A, B. There are a great many natural enemies of garden pests, including various insects such as (A) mantids, spiders such as a (B) jumping spider, predatory mites, and centipedes. WHITNEY CRANSHAW
NATURAL ENEMIES OF INSECTS AND POLLINATORS: THE “BENEFICIAL BUGS”
ENTOMOLOGISTS OFTEN NOW USE the term “services” to describe the beneficial roles that insects and related invertebrates perform in our environment. Activities of these organisms are normally unseen by the average observer, but they contribute to all aspects of a healthy garden ecosystem. Without the services of insect natural enemies, populations of pest species would go largely unchecked. Other insects—along with many mites, millipedes, sowbugs, and earthworms—are macrodecomposers that handle the large amount of dead plant matter, dead animals, and animal waste that is constantly being produced, preventing it from piling up and allowing the nutrients locked within to be released into the nutrient cycling system. Furthermore, a very large percentage of flowering plants, including most of our fruits and vegetables, are pollinated by a host of bees, flies, beetles, butterflies, moths, and other insects.
There are several kinds of natural controls that work to regulate populations of all insects. Weather-related events, such as periods of extreme temperatures or heavy rainfall, can sometimes have enormous adverse effects on insects and mites. Many plants have some ability to fight off pests (host plant resistance), producing chemicals toxic to a feeding insect or stimulating physical defenses, such as a pitch flow that can entrap attacking insects. Physical features of some plants, such as hairs or a waxy surface, can also deter and prevent successful insect attack.
Perhaps the most widely recognized of the natural controls, however, and most observable to the gardener, are the natural enemies of insects. Three primary groups of natural enemies predominate: predators, parasitoids, and pathogens, examples of which are described in the following section. Although these are constantly active under natural conditions, there are occasions when humans seek to enhance their activities to be more effective in suppressing a particular plant pest. This human intervention with natural enemies is then described as biological control. One way this can be done is to acquire a natural enemy through a commercial supplier; more than four dozen natural enemy species are commercially available. These might be introduced into a crop where they do not already exist, such as introducing a whitefly parasitoid for control of greenhouse whitefly, or to augment numbers of an existing natural enemy, such as when one distributes green lacewing eggs in a garden. The purchase and release of some insects is quite widely known in the gardening community, notably releasing adults of field-collected convergent lady beetles or placement of egg cases of the Chinese mantid in a garden.
Although use of these “bugs for hire” is fairly popular, it is a far less efficient and effective biological control strategy than methods that conserve and enhance the existing natural enemies already present in a yard and garden. These involve purposeful efforts to improve the environment in ways that meet needs of the natural enemy species. For example, adult stages of many insect predators (e.g., lady beetles, green lacewings, flower flies, hunting wasps) sustain themselves on nectar and/or pollen. By purposefully planting the types of flowers that are used as nectar and pollen sources, their activities can be optimized. Diversification of plantings can improve the availability of different kinds of prey that can be used to sustain larval stages of insect predators. Some insects, notably certain hunting wasps (and many solitary bees), need nesting sites, which may be in the form of small holes or cavities in wood. Also, it is very important that any other insect control practices, such as use of insecticides, be done only in a manner that minimizes effects on natural enemy species, that is, that fully integrate natural controls with other management methods.
A, B. There are a great many natural enemies of garden pests, including various insects such as (A) mantids, spiders such as a (B) jumping spider, predatory mites, and centipedes. WHITNEY CRANSHAW
C. Macrodecomposers such as earthworms help recycle the nutrients present in dead plant and animal matter. WHITNEY CRANSHAW
D, E. Many plants are dependent on pollination by insects such as (D) bees (E) butterflies, moths, beetles, and flies. WHITNEY CRANSHAW
F. A few organisms that can provide biological control of other insects are commercially available, such as these field-collected convergent lady beetles. MATT CAMPER, COLORADO STATE UNIVERSITY
G, H. Adult stages of many insect natural enemies sustain themselves on nectar or pollen or both, such as (G) flower flies (H) hunting wasps. WHITNEY CRANSHAW
PREDATORS OF INSECTS AND MITES
A great many kinds of insects—as well as all spiders and centipedes and many mites—develop as predators of insects or other arthropods. Arthropods that are predators are free-living hunters in their immature stages, actively seeking prey, and they consume many prey in the course of their development. Adult stages of insect predators may have similar habits, particularly those that have simple metamorphosis (e.g., mantids, predatory bugs) as well as spiders and predatory mites. Other kinds of insect predators switch diet in the adult stage to feed largely or exclusively on nectar, pollen, honeydew, and similar materials. The availability of these adult food sources allows them to survive longer and often to lay more eggs.
LADY BEETLES (LADYBUGS, LADYBIRD BEETLES)1
Lady beetles are the most familiar and widely recognized predators of garden insects. Adults of the great majority have a characteristic round-oval shape, are brightly colored, and often have bold patterning on the wing covers. A pattern of black spots on an orange or reddish background is present on many of the most commonly encountered species, including CONVERGENT LADY BEETLE (Hippodamia convergens), TWOSPOTTED LADY BEETLE (Adalia bipunctata), SEVENSPOTTED LADY BEETLE (Coccinella septempunctata), and MULTICOLORED ASIAN LADY BEETLE (Harmonia axyridis); however, other common lady beetles have variations of color and patterning, such as the PARENTHESIS LADY BEETLE (Hippodamia parenthesis), VARIEGATED LADY BEETLE (H. variegata), PINKSPOTTED LADY BEETLE (Coleomegilla maculata), EYESPOTTED LADY BEETLE (Anatis mali), and TWICESTABBED LADY BEETLE (Chilocorus stigmata). Many lady beetles may be uniformly colored, black or gray, and a few are striped.
Many lady beetles are generalist predators that feed on many kinds of insects and mites, including aphids, small caterpillars or beetles, and insect eggs. Many of the most commonly observed species feed primarily on aphids, although other prey may be incidentally eaten, but other lady beetles are more specialized predators. For example, the twicestabbed lady beetle feeds only on armored scales, and the SPIDER MITE DESTROYERS (Stethorus species) feed on mites. The larvae of all are strictly predators, but adults of most species also supplement their diet with pollen, nectar, and honeydew, and the presence of such foods around the yard or garden may be important in maintenance of these beneficial insects. When prey or alternate sources of nourishment are not available, adult lady beetles readily disperse to search other sites for food.
Most lady beetles lay eggs in masses of 5–30 orange-yellow eggs. The eggs are quite distinctive, being round with pointed tips, although they can resemble those produced by some leaf beetles (Chrysomelidae family). Eggs are usually laid near colonies of insects that provide food for their larvae.
The immature or larval stages look very different from the adult beetles and are often overlooked or misidentified. Lady beetle larvae are elongated, generally dark colored, and usually marked with orange, yellow, or purple, or combinations of these. Some species may have fleshy spines and a few that specialize on mealybugs and woolly aphids as prey are covered with white wax. Larvae are active hunters that can crawl rapidly over plants, searching for food. This very different appearance of the immature forms can sometimes be confusing to gardeners, who may even mistake them for pest insects—but the larval stage of the lady beetles is, by far, the most important stage in terms of preying on other insects, consuming far more than the adults.
B. Twospotted lady beetle. WHITNEY CRANSHAW
C. Sevenspotted lady beetle. WHITNEY CRANSHAW
D. Multicolored Asian lady beetle. WHITNEY CRANSHAW
E. Pinkspotted lady beetle. DAVID SHETLAR
F. Parenthesis lady beetle. WHITNEY CRANSHAW
G. Spider mite destroyer. WHITNEY CRANSHAW
H. Twicestabbed lady beetle. DAVID SHETLAR
I. Lady beetle egg mass. DAVID SHETLAR
J. Lady beetle egg mass laid on tree trunk. HAROLD J. LARSEN, COLORADO STATE UNIVERSITY
The larval stage of lady beetles is often completed in two or three weeks. They then seek out a place to pupate, which may be on leaves, trunks, sides of buildings or other solid surfaces. The pupa is attached to these objects at the base of the abdomen and during this period will not move, except to twitch sometimes when disturbed. The adult stage will typically emerge a week or two after the pupa is formed, and the pupae often become increasingly darker and more patterned as adult emergence approaches.
Most lady beetles survive winter as an adult in sheltered locations, such as under leaves, behind bark flaps, and sometimes behind walls of buildings. Most lady beetles spend winter alone or in small groups, but in some areas of the country the convergent lady beetle migrates to higher elevations during its dormant periods and may aggregate in large numbers. These mass aggregations, particularly those that occur in the Sierra Nevada Mountains, serve as the source of adult lady beetles that are then sold through nursery and garden catalogs. Although the sale and release of these wild-caught convergent lady beetles has long been a common and popular practice, it has little value for a gardener since almost all the beetles immediately disperse from the area. Furthermore, the field-collected beetles are in a semidormant stage (diapause) and will normally not begin to lay eggs for several weeks following their release.
Several lady beetles present in yards and gardens are not native to North America, notably the sevenspotted lady beetle and multicolored Asian lady beetle. The latter derives its name from having considerable variation in coloration and spotting. It is now often one of the most common lady beetles encountered in yards, gardens, and crop fields and a voracious predator of aphids. Unfortunately, the multicolored Asian lady beetle, unlike the native species, has a habit of entering buildings in late summer and early fall, sometimes creating serious nuisance problems. They are also capable of producing a mild nip.
Convergent lady beetle (top to bottom) pupa, recent pupa that has not yet darkened, prepupa. WHITNEY CRANSHAW
Several other specialist lady beetles have also been introduced into North America. Lindorus lophanthae, known as the “singular black lady beetle,” is commonly sold as a biological control of armored scales. This native of Australia is only about ⅛ inch in diameter, and the larvae can actually fit under the shells of scales. Cryptolaemus montrouzieri, known as the MEALYBUG DESTROYER, is another commonly sold species used to manage citrus mealybug in citrus orchards, greenhouses, and interiorscapes. Perhaps the most famous lady beetle is the VEDALIA BEETLE (Rodolia cardinalis), which was purposefully imported into California to control the cottony cushion scale on citrus trees in 1888. This introduction was spectacularly effective in eliminating cottony cushion scale as a serious pest, and it provided the first clear demonstration, worldwide, of the potential value of biological control for managing insects and mites.
About 480 species of lady beetles can be found throughout North America and, with very few exceptions, all develop as predators of other insects and mites; in addition, there are seven North American species in the genus Psyllobora that feed on fungi, particularly powdery mildews. These are all considered beneficial inhabitants of the yard and garden. A notable exception are the “bad apples” of the lady beetle family: the Mexican bean beetle and squash beetle (page 204), which have a plant-feeding habit.
1 Coleoptera: Coccinellidae
B. Larva of the convergent lady beetle. WHITNEY CRANSHAW
C. Larva of the multicolored Asian lady beetle. WHITNEY CRANSHAW
D. Larva of the sevenspotted lady beetle. WHITNEY CRANSHAW
E. Massed convergent lady beetles in overwintering site. JIM KALISCH, UNIVERSITY OF NEBRASKA
F. Larva of the mealybug destroyer lady beetle. DAVID CAPPAERT, BUGWOOD.ORG
G. Range of color and patterning of multicolored Asian lady beetle, a species that enters buildings during the dormant season. DAVID SHETLAR
H. A vedalia beetle next to a cottony cushion scale. JACK KELLY CLARK COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
I. A Psylloborus species of lady beetle that feeds on powdery mildew. WHITNEY CRANSHAW
GROUND BEETLES1
Ground beetles are common insects of gardens. Most are broadly oval in form, with prominent forward-projecting jaws. They have hard wing covers that are typically dark, but they may have metallic coloration. Adults can be very active and fast moving, although they usually spend days under cover of leaf litter and other sheltering debris. Larvae are soft-bodied, elongate, and also predators. Larvae are usually active at the soil surface or tunnel in the upper soil.
Almost all ground beetles develop as predators and may feed on a wide variety of insects, snails, and slugs. As their name may indicate, most restrict their activity to areas at or around the soil surface and are poor climbers; however, a few species may occur on plants, such as the large, striking Calosoma species, known as “caterpillar hunters,” that attack larvae of gypsy moth and other caterpillars. Bembidion ground beetles can be important predators of insect eggs on leaves.
Some of the most common species belong to the genus Harpalus, which contains more than 400 species of beetles that range from iridescent green to shiny black. Poecilus is another large genus with typically green to blue-green beetles. Bombardier beetles (like Brachinus spp.) are notable for their unique defensive ability, involving production of a noxious spray at near boiling temperature that they shoot from the tip of the abdomen. Somewhat atypical ground beetle forms occur with Scarites spp. These have the head and first section of the thorax (pronotum) joined tightly together and separated from the wings and abdomen by a narrowed constriction.
A group of insects now commonly classified with the ground beetles are the TIGER BEETLES. These are extremely active insects and most readily fly. Both adults and larvae are general predators of other insects, although larvae hunt primarily by ambush from soil tubes where they develop. Most tiger beetles are in the genus Cicindela.
Soil burrows of a tiger beetle. WHITNEY CRANSHAW
Tiger beetle, Cicindela punctulata. WHITNEY CRANSHAW
Larva of the tiger beetle Cicindela punctulata, extracted from burrow. WHITNEY CRANSHAW
1 Coleoptera: Carabidae
B. Harpalus affinis. DAVID SHETLAR
C. Amara apricana. DAVID SHETLAR
D. Calasoma scrutator. DAVID SHETLAR
E. A bombardier beetle. DAVID SHETLAR
F. Ground beetle larva feeding on cutworm. JIM KALISCH, UNIVERSITY OF NEBRASKA
G. Ground beetle larva. DAVID SHETLAR
ROVE BEETLES1
Rove beetles have an unusual appearance with a very elongate body and very short wing covers, which do not even extend to cover the abdomen. It is an extremely diverse and abundantly represented family of insects, considered by many the largest family of any animal or plant on earth, with more than 63,000 described species. Many develop as predators of insects and mites, particularly of insects found in soil. Other rove beetles are scavengers of carrion or feed on dung or fungi.
Rove beetles feeding on maggot. JIM KALISCH, UNIVERSITY OF NEBRASKA
Larvae of many rove beetles found in and around yards and gardens specialize in attacking fly maggots and puparia around compost piles and other sites with decomposing plant matter. Aleochara bilineata is an introduced species that has spread widely and is an important predator of root maggots. Rove beetles in the genus Platydracus are larger and known to attack cutworm and armyworm larvae. When exposed, these beetles have a habit of curling the abdomen upward and over the body, in a somewhat threatening manner.
The tiny Oligota oviformis is sometimes called the “spider mite destroyer” as the larvae and adults feed on spider mites that attack fruits and ornamental plants in the garden. The greenhouse rove beetle Dalotia (=Atheta) coriaria is a small black species commonly sold for control of fungus gnat larvae. These are most useful in greenhouses, enclosed environments, and gardens that have suitable hiding places and moisture.
1 Coleoptera: Staphylinidae
SOLDIER BEETLES1
Soldier beetles are elongate beetles with fairly soft wing covers, lending them the alternate name “leather-winged beetles.” Adults are usually patterned with yellow or orange and black markings. Soldier beetles are most commonly observed on yellow flowers late in the season, feeding on pollen and often in copula. Some (Cantharis and Podabrus species) can be important predators of aphids, mealybugs, and other soft-bodied insects.
A Cantharis species of soldier beetle. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
The rarely noticed larval stages are elongate and covered with a velvet-like integument. They develop in the soil where they feed on other arthropods, but they occasionally invade homes in search of food. Larvae of the common PENNSYLVANIA LEATHERWING (Chauliognathus pensylvanicus) are reported to develop as predators of root maggots in soil.
1 Coleoptera: Cantharidae
B. Rove beetle. WHITNEY CRANSHAW
C. Rove beetle. DAVID SHETLAR
D. Rove beetle larva. DAVID SHETLAR
E. A Podabrus species of soldier beetle. JIM KALISCH, UNIVERSITY OF NEBRASKA
F. Soldier beetle larva. DAVID SHETLAR
G. Pennsylvania leatherwing. DAVID CAPPAERT, BUGWOOD.ORG
BLISTER BEETLES1
Blister beetles can have many kinds of associations with a garden. The adults are plant feeders, with many common at flowers feeding on pollen (page 566) and a few occasional plant pests that chew leaves of various legumes, clematis, and other garden plants (page 206). The larval stages develop as predators of various insects. Those in the genus Epicauta feed on the eggs of grasshoppers, and their abundance often cycles with the numbers of their prey. The brightly colored Lytta species and large flightless “oil beetles” (Meloe spp.) develop while feeding on the food and larvae of developing bees and wasps that nest in the ground.
Blister beetle larva. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
1 Coleoptera: Meloidae
FIREFLIES/LIGHTNINGBUGS1
Despite their common names, fireflies or lightningbugs are neither flies nor bugs, but instead are a type of beetle. Like soldier beetles and blister beetles, fireflies have fairly soft wing covers and are elongate in form. The head is usually hidden below a flap of the first thoracic segment and many species (but not all) have light organs on the tip of the abdomen used to flash mating signals.
Larvae of fireflies are usually found in moist sites, where they feed on soft invertebrates such as slugs, snails, and earthworms. They are much more abundant east of the Great Plains than in western states, and species that produce light are particularly uncommon in western North America. Adults of some fireflies may also be predatory, feeding on scale crawlers, aphids, and similar small, soft-bodied insects.
1 Coleoptera: Lampyridae
SOFT-WINGED FLOWER BEETLES1
Soft-winged flower beetles are moderate-sized beetles (⅕ to ⅓ inch), usually bluish-black with red or orange markings. They are typically observed on flowers, where they may feed on pollen, but some are also predatory and will feed on insect larvae, aphids, and other small, soft-bodied insects. They can be common in fields but are infrequently found in gardens, and members of the genus Collops are considered important predators of insects in many crops, particularly in the western states. Larvae also develop as predators but live in the soil and are rarely observed.
1 Coleoptera: Melyridae
B. A first-instar larva of a blister beetle (triungulin). KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
C. A nocturnal, luminescent firefly, Photinus pyralis. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. A day-active, non-luminescent firefly, Ellychnia corrusca. DAVID CAPPAERT, BUGWOOD.ORG
E. Larva of a firefly. DAVID SHETLAR
F. Larva of a firefly. GERALD J. LENHARD, LOUISIANA STATE UNIVERSITY, BUGWOOD.ORG
G. Collops beetle feeding on weevil larva. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
CLERID BEETLES1
Clerid beetles, or checkered beetles, are usually brightly colored insects that are generally elongate in form and somewhat flattened. Most species are important predators, as adults and larvae, of bark beetles and other wood-boring beetles. The adult beetles are commonly found inspecting the trunks of dead trees or logs, where they are searching for food or egg-laying sites. The adults also frequently visit flowers. The immature clerid beetles are commonly found in tunnels of bark beetles.
1 Coleoptera: Cleridae
CYBOCEPHALID BEETLES1
The cybocephalids are relatives of sap beetles, but they have a predatory habit. Most are specialists of armored scales, but some feed on adelgids, mealybugs, and mites. The adult beetles are small, elongate-oval in shape, and either black or bicolored. The larvae look somewhat like small lady beetle larvae. Cybocephalus nipponicus has been introduced into the eastern U.S. to control the hemlock elongate scale, and in Florida to control the cycad scale. Native species in this genus also feed on armored scales.
1 Coleoptera: Cybocephalidae
GREEN LACEWINGS1
Several species of green lacewings commonly frequent yards and gardens, most in the genera Chrysopa or Chrysoperla. Adults are generally pale green insects with clear, highly veined wings they hold over the body when at rest. Some species turn a light brown during cold weather. They are delicate and very attractive insects that feed primarily on nectar, pollen, and honeydew, although adults in the genus Chrysopa also feed on small insects. The females lay a distinctive stalked egg, approximately ½ inch in height. Eggs may be laid in small groups or singly on leaves of plants throughout the yard.
Lacewing larvae emerge from the egg in about a week. These larvae, sometimes called “aphid lions,” are voracious predators capable of feeding on a wide range of insects, including small caterpillars and beetles as well as aphids and other insects. They are perhaps best marked by their large sickle-shaped jaws that project from the head. The body is elongate, usually a bit thicker in the middle, and most lacewing larvae are some shade of light brown to nearly white. However, these features are obscured by the larvae of some “trash-carrying” species that pile the carcasses of prey, small bits of lichen, and other debris on their body, an effective camouflage from some predators that also allows them to escape detection by aphid-tending ants. Pupation occurs in a nearly spherical, pale-colored cocoon often attached loosely to leaves or needles.
Some Chrysoperla species are produced commercially in insectary facilities. These are sold, often as eggs, for use in biological control of aphids and caterpillars in certain vegetable and greenhouse crops and interiorscapes.
1 Neuroptera: Chrysopidae
A. Checkered beetle feeding on bark beetle. GERALD J. LENHARD, LOUISIANA STATE UNIVERSITY, BUGWOOD.ORG
B. Checkered beetle feeding on emerald ash borer. DAVID CAPPAERT, BUGWOOD.ORG
C. Larva of a checkered beetle. WHITNEY CRANSHAW
D. A cybocephalid feeding on hemlock scales. DAVID SHETLAR
E. Green lacewing eggs. DAVID CAPPAERT, BUGWOOD.ORG
F. Green lacewing adult. WHITNEY CRANSHAW
G. Green lacewing adult. DAVID SHETLAR
H. Green lacewing larvae shortly after egg hatch. WHITNEY CRANSHAW
I. Late-instar larva of a green lacewing. DAVID SHETLAR
J. A “trash-carrying” larva of a green lacewing. SUSAN ELLIS, BUGWOOD.ORG
K. Cocoon surrounding green lacewing pupa. WHITNEY CRANSHAW
BROWN LACEWINGS1
The brown lacewings are related to the green lacewings with generally similar habits, being predators of insects as both adults and larvae. Many are more specialized predators, feeding primarily on woolly aphids, mealybugs, scales, and mites, and they are usually associated with dense vegetation, including trees and shrubs.
Adult brown lacewings are generally smaller than green lacewings, possess light brown wings, and are predators. Larvae are also predators, with a body generally similar to green lacewings but with mouthparts that are a bit less curved and a narrower body form. The eggs of brown lacewings are laid singly on foliage and do not have a stalk.
1 Neuroptera: Hemerobiidae
DUSTYWINGS1
Dustywings are very small insects (ca. ⅛ inch) that develop as predators of mites, but they may also feed on aphids, scale insects, and other small arthropods. The body of the adult insect is covered with fine powdery white wax; larvae are plump with short, projecting mandibles. Although easily overlooked, dustywings may be abundant on the trees and shrubs they frequent, especially conifers.
Dustywing larva. DAVID SHETLAR
1 Neuroptera: Coniopterygidae
ANTLIONS1
The larvae of antlions are predators that establish cone-shaped pits in loose soil to trap insects that wander into the pit traps. Sometimes known as “doodlebugs,” the larvae have a generally oval body with prominently projecting elongate jaws (mandibles). They are ambush hunters that lie in wait, buried at the base of the pit, for passing prey.
The adults are rarely noticed since they fly at night. The adults drop eggs onto dry soil, and upon hatching, the larvae scoot backwards in a spiral while flipping out fine soil or sand. This eventually forms a pit with steeply sloping sides. Any insect that drops into the pit is quickly grabbed by the jaws and pulled down into the soil where the body fluids are sucked out. Antlions are likely not major predators in landscapes, but interesting curiosities.
1 Neuroptera: Myrmelionidae
B. Brown lacewing larva. DAVID SHETLAR
C. Brown lacewing larva feeding on aphid. DAVID CAPPAERT, BUGWOOD.ORG
D. Dustywing. DAVID SHETLAR
E. Antlion adult. WHITNEY CRANSHAW
F. Antlion larva. DAVID SHETLAR
G. Antlion larva feeding on cricket. JIM KALISCH, UNIVERSITY OF NEBRASKA
H. Pits produced by antlion larvae. DAVID SHETLAR
SYRPHID FLIES (FLOWER FLIES, HOVER FLIES)1
Syrphid flies are common, brightly colored flies most often seen at flowers, where they feed on nectar. Adults are typically marked with yellow or orange and black in a manner that can closely mimic certain bees or wasps; however, syrphid flies are incapable of biting or stinging and are harmless to humans.
It is the larval stage of the syrphid fly that is an insect predator. Variously colored, the tapered maggots crawl over plants, and a single maggot can tear through dozens of aphids in a day. Syrphid fly larvae are particularly important in controlling aphid infestations early and late in the season, when many other predators are not active, and their body form also allows them to enter tightly curled leaves where aphids hide. Despite being common and abundant, the larvae are infrequently noticed as they are slow moving and often blend well with the plants. Indirect evidence of their prior activity is sometimes present on plants in the form of a tarry smear of excrement they leave behind after feeding on aphid prey.
Although most syrphid flies seen in gardens develop as predators of insects, others have different habits. A few species of syrphid flies, known as bulb flies (page 502), develop by feeding on and tunneling plant tissues. Also common may be DRONE FLIES (Eristalis species), excellent mimics of honey bees. In their larval form—known as a RATTAI LED MAGGOT because of the very long breathing tube that extends from the end of the abdomen—drone flies develop in very moist soil or polluted water.
1 Diptera: Syrphidae
PREDATORY MIDGES1
Although most insects of the gall midge family Cecidomyiidae feed on plants and many produce galls or other plant distortions, a few are predators of other insects. The larvae are tiny maggots (ca. 
inch), often orange or yellowish and found on leaves among colonies of their prey. The most common species encountered in gardens is Aphidoletes aphidimyza, a predator of aphids, and Feltiella acarisuga, a predator of spider mites. Both of these are also commercially reared and sold for control of greenhouse pests.
1 Diptera: Cecidomyiidae
B. Syrphid fly, Helophilus species. JIM KALISCH, UNIVERSITY OF NEBRASKA
C. Syrphid fly, Toxomerus species. JONATHAN YOUSCHOCK
D. Syrphid fly laying egg in aphid colony. DAVID SHETLAR
E. Syrphid fly egg. DAVID SHETLAR
F. Syrphid fly larva. DAVID SHETLAR
G. Drone fly (top) and honey bee (bottom). WHITNEY CRANSHAW
H. Syrphid fly larva. JIM KALISCH, UNIVERSITY OF NEBRASKA
I. Larva of a drone fly, a rattailed maggot. JIM KALISCH, UNIVERSITY OF NEBRASKA
J. Spider mite predator midge, Feltiella acarisuga. WHITNEY CRANSHAW
K. Aphid predator midge, Aphidoletes aphidimyza. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
The long-legged flies1 are moderately small flies noted for their metallic coloration. Species of Condylostylus are common across North America, with all species being metallic green, blue, or copper. Less noticed are species of Gymnopternus and Xanthochorus, which are yellow or brown with darker markings. Adult stages of both flies have prominent eyes and long legs. Adults feed on small insects such as gnats and midges. Larvae are also predaceous and some (Medetera species) live under bark and feed on bark beetle larvae.
Dance flies2 are closely related to longlegged flies but lack the metallic coloration, and most are brown, gray, or black. Dance flies are most commonly observed perched on plant leaves, where they are looking for potential prey to fly by. When approached, these flies often run back and forth on leaf surfaces, quickly moving from one leaf to another. The LONGTAILED DANCE FLY, Rhamphomyia longicauda, is a woodland species that is easy to spot because of its large red eyes and feather-shaped bristles that line the legs. It can occasionally be found in shaded garden locations.
1 Diptera: Dolichopodidae
2 Diptera: Empididae
ROBBER FLIES1
Along with dragonflies, the robber flies are often the top predators of the airways over a field or garden. Robber flies vary considerably in size, but many are fairly large and almost all have a characteristically elongated abdomen. They have large eyes, used to scan the area where they perch, and a sharp beaklike mouthpart, hidden within a “mustache” of hairs. The adults are active fliers that will dart after any other insect that flies by, which they grasp with their front legs and rapidly paralyze with a bite. They are generalist predators and will attempt to attack almost any insect of sufficient size to attract their interest. The larvae live in moist soil or decaying logs, where they also prey on other soft-bodied insects.
Members in the subfamily Asilinae are often called giant robber flies, and species of Machimus and Proctacanthus can be found in most landscapes. Adults can range from 1 to 2 inches in length. On the other extreme, members of the subfamily Stenopogoninae are usually ½ inch or less in length, and most have yellow and black markings that mimic local wasps. The thinnest of the robber flies are species in the subfamily Leptogastrinae that can actually mimic crane flies. Species of Leptogaster are often seen perched on the top of a plant holding their abdomen straight out from the plant. Species in the subfamily Laphriinae are medium to large flies, and most have hairy bodies that mimic bees. Species of Laphria can look so much like bumble bees that most people simply walk by them.
1 Diptera: Asilidae
B. Longlegged fly feeding on small fly. DAVID SHETLAR
C. Dance fly. DAVID SHETLAR
D. Dance fly, Rhamphomyia longicauda. DAVID SHETLAR
E. Robber fly feeding on cabbage butterfly. WHITNEY CRANSHAW
F. Robber fly feeding on honey bee. WHITNEY CRANSHAW
G. Robber fly adult emerging from pupal case. WHITNEY CRANSHAW
BEE FLIES1
Bee flies are typically moderate-sized flies with a rounded body often covered with hairs, giving them a superficial resemblance to a bee. The wings often have brown or black markings, and many have elongated mouthparts used to suck nectar from flowers, their main food. The larvae develop as predators or external parasites of other insects. Many bee flies develop on host larvae of ground-nesting bees, but others develop on grasshopper eggs and the larvae and pupae of beetles, moths, flies, and wasps. They range widely in size, with the largest, Xenox spp., being parasites of carpenter bee larvae.
1 Diptera: Bombyliidae
PREDATORY THRIPS1
Adults of the PREDATORY THRIPS1 are usually dark colored and often conspicuously marked with black-and-white banding, lending them the alternative name “bandedwinged thrips.” Most feed primarily on smaller prey, notably spider mites and plant feeding thrips, but they may take other prey and supplement their diet with pollen. Most occur in the genus Aeolothrips, which has 31 North American species, but other predatory thrips that may be locally common include Franklinothrips vespiformis,1 with a body form that mimics ants, and Leptothrips mali (BLACK HUNTER THRIPS),2 the most important predatory thrips in eastern orchards. A species sold for biological control is the SIXSPOTTED THRIPS (Scolothrips sexmaculatus),3 used to control spider mites.
Predatory thrips, Franklinothrips vespiformis. WHITNEY CRANSHAW
1 Thysanoptera: Aeolothripidae
2 Thysanoptera: Phlaeothripidae
3 Thysanoptera: Thripidae
PREDATORY STINK BUGS1
Although stink bugs include many species that feed on plants (pages 300 and 594–596), some are predators. All stink bugs are characterized by their distinctive shieldlike body and ability to produce an unpleasant odor when disturbed. Those that feed on insects are capable of subduing large prey, such as caterpillars or beetle larvae, which they impale with piercing-sucking mouthparts. Among the predatory stink bugs commonly found in gardens are the TWOSPOTTED STINK BUG (Perillus bioculatus) and related Perillus species, which specialize in beetle larvae and the SPINED SOLDIER BUG (Podisus maculiventris) and related Podisus spp., which feed primarily on caterpillars. A particularly colorful species found in the southeastern states is the FLORIDA PREDATORY STINK BUG (Euthyrhynchus floridanus). Immature stages of most predatory stink bugs, which lack fully developed wings, are generally rounded in body form and may have colorful patterning.
Most stink bugs feed on plants and are discussed in other sections. Those that are predatory can be distinguished from the plant feeding stink bugs by viewing the attachment of the mouthparts at the front of the head. The mouthparts of predatory species are attached only at the tip, allowing them to project forward when stalking prey. Mouthparts of plant-feeding stink bugs are attached more extensively to the head and can only be directed downward.
1 Hemiptera: Pentatomidae
B. Bee fly, Villa species. WHITNEY CRANSHAW
C. Sixspotted thrips. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
D. Predatory thrips, Aeolothrips species. WHITNEY CRANSHAW
E. Spined soldier bug nymph feeding on caterpillar. RUSS OTTENS, UNIVERSITY OF GEORGIA, BUGWOOD.ORG
F. Spined soldier bug. DAVID SHETLAR
G. Spined soldier bug eggs. DAVID SHETLAR
H. Florida predatory bug. JOHNNY N. DELL, BUGWOOD.ORG
H. Twospotted stink bug feeding on Colorado potato beetle larva. JOHN CAPINERA, UNIVERSITY OF FLORIDA
ASSASSIN BUGS1
Assassin bugs are moderately large insects that can also feed on fairly large prey, such as insect larvae. Most assassin bugs are elongate in form, have a pronounced “snout” on the front that is the base for the stylet mouthparts, and are spiny. Despite their prodigious ability to dispatch most garden pests, they rarely become very abundant, since they in turn succumb to many natural enemies of their own, including fellow assassin bugs. Common assassin bugs associated with gardens include the SPINED ASSASSIN BUG (Sinea diadema) and related Sinea spp., the BEE HUNTERS (Apiomerus spp.), and several elongate assassin bugs in the genus Zelus. Of even more dramatically slender form are the THREAD-LEGGED BUGS (Emesaya species), which have grasping front legs and can be mistaken for very thin mantids. The thread-legged bugs often feed on spiders and are able to move among spider webs.
One of the largest assassin bugs is the WHEEL BUG (Arilus cristatus), which can reach nearly 2 inches in length. They are an overall dark gray color and the pronotum behind the head has a series of distinctive, upright spines that look like the spokes of a wheel. This is a generalist predator that will feed on anything it can capture. The eggs of this species are often found as a mass of barrel-shaped eggs glued together in a flat mass with a dark resinlike material. The nymph has a red, bulbous abdomen.
Late in the season, AMBUSH BUGS (Phymata species) are commonly found on flowers. These are rather heavy-bodied assassin bugs with thick forelegs they use to capture flies, bees, and other insects that visit flowers. Their patterning and coloration blend well with the flowers on which they hide.
Zelus luridus nymph feeding on hunting wasp. WHITNEY CRANSHAW
Ambush bug feeding on honey bee. DAVID SHETLAR
All assassin bugs of sufficient size can bite humans if handled. The bite is often quite painful but of short duration and not a medical threat.
1 Hemiptera: Reduviidae
DAMSEL BUGS1
Damsel bugs are considerably smaller than assassin bugs (ca. ¼ inch) and usually dark yellow to pale brown or mottled gray. Similar to the assassin bugs, the forelegs are slightly thickened to assist in holding prey. Damsel bugs develop as general predators of insect larvae, small soft-bodied insects, and insect eggs. They are most common in grassy fields.
1 Hemiptera: Nabidae
B. Wheel bug. DAVID LEATHERMAN
C. Zelus luridus. WHITNEY CRANSHAW
D. Egg mass of the assassin bug Zelus luridus and nymph. WHITNEY CRANSHAW
E. Threadlegged bug. DAVID SHETLAR
F. Ambush bug eggs and newly hatched nymph. WHITNEY CRANSHAW
G. Damsel bug. WHITNEY CRANSHAW
H. Damsel bug nymph. BRADLEY HIGBEE, ARAMOUNT FARMING, BUGWOOD.ORG
PREDATORY PLANT BUGS1
The plant bug family includes several important species that can be seriously damaging to plants, such as the tarnished plant bug (page 592), fourlined plant bug, and honeylocust plant bug (page 296); however, many plant bugs are omnivorous and frequently feed on insects as well as plants. A few, notably in the genus Deraeocoris, are primarily predaceous and on some plants may be among the most important biological controls of spider mites, gall midges, and other pests of shade trees.
1 Hemiptera: Miridae
BIG-EYED BUGS1
Big-eyed bugs are common predators in gardens, lawns, and field crops. Adults of most are gray, black, or tan in color and about ⅛ inch long; the wingless nymphs have a lighter-colored body. Similar in general appearance to many small seed or plant bugs, the big-eyed bugs are distinguished by having very large eyes along the sides of the head. They are active insects, and both nymphs and adults may be seen rapidly running in search of small insects, mites, or insect eggs. Almost all big-eyed bugs are in the genus Geocoris, with G. pallens and G. punctipes two of the common gray-colored representatives and G. uliginosus a common generally black species.
Big-eyed bug feeding on leafhopper. RUSS OTTENS, UNIVERSITY OF GEORGIA, BUGWOOD.ORG
1 Hemiptera: Geocoridae
MINUTE PIRATE BUGS1
The smallest of the predatory “true” bugs commonly found in yards and gardens (typically about 
inch), minute pirate bugs feed on smaller arthropods such as spider mites, thrips, aphids, and insect eggs. The adults in the genus Orius are distinctive with black-and-white markings; Xylocoris spp. tend to be more uniformly colored dark gray or brown. Immature forms of minute pirate bugs are generally red or straw-colored and may superficially resemble a highly active aphid. Minute pirate bugs are most often seen in and around flowers, where they feed on thrips or, in the absence of prey, pollen and nectar.
1 Hemiptera: Anthocoridae
A. Predatory plant bug Deraeocoris brevis. BRADLEY HIGBEE, PARAMOUNT FARMING, BUGWOOD.ORG
B. Nymph of the predatory plant bug Deraeocoris brevis. BRADLEY HIGBEE, PARAMOUNT FARMING, BUGWOOD.ORG
C. Big-eyed bug nymph feeding on chinch bug. DAVID SHETLAR
D. Minute pirate bug, Orius species. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
E. Nymph of a minute pirate bug, Orius species. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
F. Minute pirate bug, Anthocoris species. BRADLEY HIGBEE, PARAMOUNT FARMING, BUGWOOD.ORG
MANTIDS1
Mantids are familiar insects to gardeners. Large and statuesque, all develop as predators of other insects, which they capture with their distinct grasping forelegs. Mantids develop from eggs that are laid in masses (an ootheca) covered with a protective layer of dried foam, giving them somewhat the appearance of a packing peanut. Immature forms resemble the adults but lack wings.
The most common mantid in much of the northern U.S. is the introduced EUROPEAN MANTID (Mantis religiosa), also known as the “praying mantid.” Both brown and green forms occur, the variation in large part related to the general color of the background vegetation where they develop, with brown forms predominating from drier sites. A bull’s-eye marking on the inside of the foreleg is a characteristic that can be used to distinguish this species.
European mantid making warning display. WHITNEY CRANSHAW
European mantid nymph recently hatched. WHITNEY CRANSHAW
Of generally similar size are several native mantids in the genus Stagmomantis. These can also be variable in color, and in females the wings do not completely cover the end of the abdomen. CAROLINA MANTID (S. carolina) occurs over a broad area east of Rockies extending into Florida. CALIFORNIA MANTID (S. californica) and S. limbata occur in the southwestern states, and the larger FLORIDA MANTID (S. floridensis) is native to Florida.
Perhaps the most familiar mantid to many gardeners is the CHINESE MANTID (Tenodera aridifolia sinensis), which has been widely distributed through sales of egg masses by garden centers and nursery catalogs. The Chinese mantid is a very large species that is generally brown with green-and-yellow striping along the sides of the wings. More recently, another non-native species related to the Chinese mantid, known as the “narrowwinged mantid” (Tenodera angustipennis), has become established in areas of the Mid-Atlantic States.
Most gardeners welcome the presence of mantids, and they are fascinating to watch; however, their ability to effectively control pests is usually far overstated. Being large and indiscriminate predators, they are too large to feed on small insects like mites, scales, and aphids. Often they hunt near flowers where they will capture bees, wasps, and other desirable species. Because of this, purchasing and distributing mantid egg cases in gardens is not recommended as a useful biological control of pests, although the practice can provide other pleasures to a gardener by increasing the very presence of mantids. (Note: It is a common myth in some areas of the U.S. that mantids are protected by law. This is without foundation, although they are the State Insect of Connecticut and South Carolina.)
1 Mantodea: Mantidae
B. Egg cases produced by European mantid. WHITNEY CRANSHAW
C. Carolina mantid male. DAVID SHETLAR
D. Carolina mantid female. DAVID SHETLAR
E. Nymph of a Carolina mantid. DAVID SHETLAR
F. Chinese mantid. DAVID SHETLAR
G. Egg case of a Chinese mantid. DAVID SHETLAR
EARWIGS1
Although the EUROPEAN EARWIG (page 52)1 is often considered a plant pest as well as a common nuisance, it is an omnivore that feeds on a wide variety of materials, including many insects. Other earwigs are primarily predaceous, however, including RINGLEGGED EARWIG (Euborellia annulipes)2 and the SPINE-TAILED EARWIGS (Doru species).3
1 Dermaptera: Forficulidae
2 Dermaptera: Anisolabididae
3 Dermaptera: Labiduridae
Dragonflies and damselflies are among the most widely recognized of the insect predators, and adults often move into yards and gardens. The adults are day-flying aerial hunters, capturing flying insects on the wing. Small flies make up much of their diet, including the occasional mosquito, but they may also catch larger prey, such as butterflies, large flies, and bees. Often they are most commonly observed to feed at dusk, when mating swarms of midges and gnats provide rich hunting.
Unlike the other natural enemies of insects found in yards, the immature stages of dragonflies and damselflies develop in water, with permanent ponds that have vegetation being particularly good breeding sites. These are top-level predators of these aquatic sites, either lying in wait as ambush hunters or slowly stalking prey. They feed mostly on a mixture of insects and crustaceans, sometimes taking tadpoles and small fish, which they grab with unique mouthparts, an extensible “lower jaw” (labium).
Immature dragonfly. DAVID SHETLAR
1 Odonata (suborder Anisoptera)
2 Odonata (suborder Zygoptera)
CRAB SPIDERS1
Crab spiders are usually distinguished by the front two pairs of legs being particularly elongated. Most have a fairly bulbous abdomen and all hunt primarily by ambush, waiting on leaves and flowers for prey to approach. The “flower crab spiders” hunt at flowers, capturing flower visitors such as flies, bees, wasps, and the occasional moth or butterfly. They are variously patterned in yellows or white to blend in well with their background. Misumena vatia and Misumenoides formosipes are the two most common flower crab spiders; these are quite similar but the latter can usually be distinguished by the presence of dark markings. There are also 18 North American Mecaphasa spp., which are hairier than the other flower crab spiders. Less commonly observed are the “bark crab spiders,” which have a flatter abdomen and are marked with grays or browns to blend in well with bark, where they typically hunt. The most common species of bark crab spiders occur in the genera Xystichus and Bassaniana.
1 Araneae: Thomisidae
B. Ringlegged earwig. DAVID SHETLAR
C. A Doru species of earwig. DAVID SHETLAR
D. Adult of the calico pennant, a skimmer type of dragonfly. DAVID SHETLAR
E. Mating pair of bluet damselflies. DAVID SHETLAR
F. Misumena vatia crab spider at blossom. WHITNEY CRANSHAW
G. Bark crab spider, Xystichus species. WHITNEY CRANSHAW
H. Crab spider, Misumenoides formosipes. DAVID CAPPAERT, BUGWOOD.ORG
JUMPING SPIDERS1
The jumping spiders are some of the most active hunters, and as their name indicates, they are capable of short (usually less than 1 inch) jumps. Most are brightly colored, and they have large eyes that allow them to track prey well. Among those with the brightest patterning are Phidippus species; the BOLD JUMPER (P. audax) is one particularly common in yards and gardens. Other common jumping spiders include various Salticus spp., such as the ZEBRA JUMPER (S. scenicus), and the more muted-colored Platycryptus spp.
1 Araneae: Salticidae
WOLF SPIDERS1
Wolf spiders are active hunters that search the ground for prey, which they run down and subdue. Some species will dig ground burrow, lined with silk, and forage the general vicinity of the burrow, often at night. Others may be active both day and night and range more widely while hunting.
Most wolf spiders are gray, brown, or nearly black, and some have lighter chevron or striping patterns that can be useful in identifications. Females are longer and more heavy-bodied than males, although legs of the latter are often proportionately longer. A distinctive habit of the females is that they carry their egg sac attached to the spinnerets at the end of the body. (Nursery web spiders also carry their egg sac, but with their jaws.) When the eggs hatch, the mother will tear open the sac and then carry the spiderlings on her back, where they remain for days, until the next molt.
Size of wolf spiders ranges widely. Some of the smaller species are in the genera Pirata and Paradosa, which typically have a body length of ¼ to ½ inch. Among the commonly noticed wolf spiders in eastern North America that is somewhat larger is Rabidosa rabida (RABID GARDEN SPIDER), and some very large wolf spiders occur in the genera Tigrosa and Hogna. Hogna carolinensis (CAROLINA WOLF SPIDER) is generally considered the largest wolf spider in North America, with the body of the females sometimes reaching almost 1½ inches, causing it to be mistaken sometimes for a tarantula—or a small mouse. None of the wolf spiders are dangerous to humans, and they will readily attempt to flee if disturbed.
1 Araneae: Lycosidae
NURSERY WEB SPIDERS1
These spiders are often confused with wolf spiders. Most remain motionless while hiding among leaves or on tree bark. Their name comes from their habit of webbing together some plant leaves in which an egg case is deposited. The female spider often guards this “nursery” until the newly hatched spiderlings are able to start looking for their own food. Two large species often cause alarm in gardens. The FOREST NURSERY WEB SPIDER, Dolomedes tenebrosus, often has a 3- to 4-inch leg span. The SIX-SPOTTED FISHING SPIDER, D. triton, can reach 3 inches in leg span and occasionally visits backyard water features.
1 Araneae: Pisauridae
B. Platycryptus species of jumping spider. JIM KALISCH, UNIVERSITY OF NEBRASKA
C. Zebra jumper. WHITNEY CRANSHAW
D. Wolf spider. DAVID SHETLAR
E. Wolf spider carrying egg sac. WHITNEY CRANSHAW
F. Wolf spider female carrying spiderlings. DAVID SHETLAR
G. Carolina wolf spider near burrow. JIM KALISCH, UNIVERSITY OF NEBRASKA
H. Nurseryweb spider. JIM KALISCH, UNIVERSITY OF NEBRASKA
I. Nurseryweb spider carrying egg sac. DAVID SHETLAR
DYSDERID SPIDERS1
The dysderid spider, Dysdera crocata, is a European species now widely distributed in North America and found in sites that harbor its primary prey, sowbugs and pillbugs. These “wood louse hunters” or “roly-poly hunters” possess very large jaws which, combined with their reddish coloration, often attract attention; they are harmless. Dysdera crocata will often enter homes through openings near ground level, and it may establish in damp basements for awhile if its sowbug prey is also present.
1 Araneae: Dysderidae
ORBWEAVERS1
The orbweaver spiders are well recognized as the masters of web spinning, with many producing beautifully patterned concentric webs in late summer and early fall. The largest of these are the “garden spiders” (Argiope spp.) that can build large, very strong webs among shrubs and tall grasses that are capable of holding grasshoppers and other large prey. The garden spiders typically mark the center of the web with bands of reflective silk, often in a zigzag pattern, known as a stabilimentum. In most of eastern North America, the BLACK-AND-YELLOW GARDEN SPIDER (A. aurantia) predominates. In the drier areas of the west the BANDED GARDEN SPIDER (A. trifasciata) is most common, while in the southeast one finds the FLORIDA GARDEN SPIDER (A. florida). All of these have a 1-year life cycle and mature in late summer and early fall. In some of the most southern areas of Florida, Texas, and California, a spring-maturing species, the SILVER GARDEN SPIDER (A. argentata), is present.
In the southeast the GOLDEN SILK SPIDER (Nephila clavipes) attracts attention with the large webs it produces, often more than 3 feet in diameter, in open areas among trees and large shrubs. The FURROW SPIDER (Larinioides cornuta) is a very common, but smaller orbweaver found in urban gardens. It often prefers to build nests under the eaves of buildings and around night lights. It usually weaves a new nest every night and hides in nearby crevices during the day.
Large orb webs are also produced by many Araneus species. Close to 50 species occur in North America, and several occur around gardens or outbuildings. Most are chunky-bodied, and some have humps on the abdomen. The best known of these is the BARN ORBWEAVER (A. cavaticus), a common spider east of the Great Plains that is the model of E. B. White’s children’s story Charlotte’s Web. (The featured spider in the book is named Charlotte A. Cavatica.) The large humps on the abdomen and some dark spotting of the PLAINS ORBWEAVER (A. gemmoides), a common species in the western states and provinces, often lead to it being referred to as the “cat-faced spider.” A species of very similar appearance found along the West Coast is A. gemma.
Barn orbweaver. TOM MURRAY
B. Typical orb web. WHITNEY CRANSHAW
C. Black-and-yellow garden spider. DAVID CAPPAERT, BUGWOOD.ORG
D. Banded garden spider female and male (upper right). WHITNEY CRANSHAW
E. Golden silk spider. DAVID CAPPAERT, BUGWOOD.ORG
F. Plains orbweaver, also known as the “cat-face spider.” WHITNEY CRANSHAW
Many also have distinctive patterning on the abdomen, such as MARBLED ORBWEAVER (A. marmoreus), SHAMROCK ORBWEAVER (A. trifolium), and LATTICE ORBWEAVER (A. thaddeus). The CROSS ORBWEAVER (A. diadematus) is a European species introduced into both the northeastern and northwestern U.S. and is steadily extending its range.
The eight Neoscona species also produce concentrically patterned webs. These somewhat resemble Araneus spiders, but they all have a smoothly oval abdomen and tend a bit smaller. Common species include the ARABESQUE ORBWEAVER (N. arabesca), WESTERN SPOTTED ORBWEAVER (N. oaxacensis), and ARBOREAL ORBWEAVER (N. crucifera).
The sharply angular projections present on the body of Micrathena species often attract attention when they are observed. The most common species occur east of the High Plains, including the SPINED MICRATHENA (M. gracilus), WHITE MICRATHENA (M. mitrata), and ARROWHEAD MICRATHENA (M. sagittata). Micrathena funebris is present in southern Arizona and southern California. Another orbweaver marked with very prominent projections extending from a broad abdomen is Gasteracantha cranciformis (SPINYBACKED ORBWEAVER), found in the southeastern states.
Spinyback orbweaver. DAVID CAPPAERT, BUGWOOD.ORG
1 Araneae: Araneaidae
LONGJAWED AND ORCHARD ORBWEAVERS1
These orbweaving spiders usually orient the orb horizontally or at a slight angle to the ground. Many longjawed spiders seem to prefer aquatic habitats, so their webs will be found near lakes, ponds, streams, and garden water features. They have very slender bodies with longs legs, but their enlarged jaws (fangs) are what catch most attention. The ORCHARD SPIDER, Leucauge venusta, is a very common species that makes its orb web below a mass of tangled webbing. Where prey is abundant, large numbers of longjawed spiders may build masses of intertwining webs among landscape and garden plants.
Orchard spider. DAVID SHETLAR
1 Araneae: Tetragnathidae
B. Shamrock spider. DAVID CAPPAERT, BUGWOOD.ORG
C. Arabesque orbweaver. DAVID CAPPAERT, BUGWOOD.ORG
D. Spined micracantha. DAVID CAPPAERT, BUGWOOD.ORG
E. Longjawed spider. DAVID SHETLAR
COBWEB WEAVER SPIDERS1
The webs produced by cobweb weaver spiders appear as disorganized tangles of webs, typically located in a sheltered areas such as under a roof, along a fence, in a corner of a greenhouse, or within a plant. The AMERICAN HOUSE SPIDER, Parasteatodea tepidariorum, is the most common species found in and around buildings in much of North America. Other common cobweb weavers are in the genus Steatoda, including the TRIANGULATE COBWEB SPIDER (S. triangulosa), S. borealis, and S. grossa. The latter two are sometimes referred to as “false black widows” because of similar body form and dark coloration of widow spiders.
American house spider. DAVID SHETLAR
While the venom of most cobweb weavers is harmless to humans, this family also contains the “widow spiders” in the genus Latrodectus, which do possess a neurotoxic venom that can produce illness in humans. Five species can be found within the U.S. with the most common including the NORTHERN BLACK WIDOW (L. variolus), BLACK WIDOW (also called SOUTHERN BLACK WIDOW) (L. mactans), and the WESTERN BLACK WIDOW (L. hesperus). The adult females of these species are generally black in color, but immature stages may have white or yellow markings on the upper surface. The males are often brightly colored with mottled white and yellow markings. In the Gulf States, there is an introduced species, often called the BROWN WIDOW (L. geometricus). This species can range from dark to light brown and often has light markings on the abdomen, and the hourglass is a light orange color. All widow spiders can be recognized by having some red to redorange marking, often in a vaguely hourglass pattern, on the underside of the abdomen.
Widow spiders do not usually like disturbance or brightly lit areas and are infrequent in gardens, preferring more protected sites such as wood piles, dark corners of outbuildings, and basement window wells. In some situations they construct webs under or near landscape lights from which they emerge at night to capture insects attracted to the lights, a habit shared by many other spiders. Widow spiders can be abundant at times, but because of their secretive habits they are rarely contacted by humans and bites are very infrequent.
1 Araneae: Theridiidae
LYNX SPIDERS1
Lynx spiders hide among vegetation and ambush passing insects. They have very spiny legs and the tip of the abdomen comes to a point. A common species that attracts attention in the southeast is GREEN LYNX SPIDER (Peucetia viridans), which is fairly large and has bright green coloration. Oxypodes scalaris (WESTERN LYNX) and Oxypodes salticus (STRIPED LYNX) are two lynx spiders that occur most broadly across North America.
1 Araneae: Oxyopidae
B. Black widow female tending egg sac. JIM KALISCH, UNIVERSITY OF NEBRASKA
C. Male western widow. WHITNEY CRANSHAW
D. Green lynx spider tending eggs. DAVID SHETLAR
E. Green lynx spider. DAVID SHETLAR
F. An Oxypodes species of lynx spider. DAVID SHETLAR
FUNNEL WEAVERS1
The funnel weaver spiders make distinct webs that include a horizontal flat sheet of web with a funnel-shaped tube at one end. Their webs are commonly found in lawns, among tall grass, in dense shrubbery, and in corners of buildings, wood piles, and other debris. Small threads extend above the sheet of webbing that can trip passing insects and cause them to fall onto the main web, where they are rapidly subdued by the spider waiting nearby in the funnel retreat.
Funnel weaver spiders are most commonly observed in late summer and early fall, as they mature, and the webs are particularly conspicuous when covered with dew. These usually involve various “grass spider” species in the genera Hololena and Agelenopsis, which are also common nuisance invaders of homes in late season. Most often found indoors are males, many of which possess grossly enlarged pedipalps used for sperm transfer.
Funnel weaver spiders in the genera Tegenaria and Eratigena may also be found both outdoors and indoors, and the BARN FUNNEL WEAVER (T. domestica) is among the most common spiders found within buildings in North America. Often attracting more attention because of their large size are Eratigena atrica and E. agrestis (“hobo spider”).
The funnel weaver spiders are very commonly mistaken for wolf spiders or brown/recluse spiders. Funnel weaver spiders are harmless to humans.
A funnel weaver, Hololena holo. WHITNEY CRANSHAW
1 Araneae: Agelenidae
PROWLING SPIDERS1
Five species of prowling spiders can be found across North America, but those most commonly encountered are in the genus Cheiracanthium. The AGRARIAN SAC SPIDER (C. inclusum) is a native species that usually has a brown body and a yellow to light green abdomen; the YELLOW-LEGGED SAC SPIDER (C. mildei) is a foreign introduction that has spread across most of North America and is usually lighter in color.
Prowling spiders are active hunters that feed at night. For a daytime retreat they usually construct a two-sided sac of silk between two leaves, under stones or loose bark, or where two walls meet. The yellow sac spider is a common home invader, where it can remain active year-round. Adult spiders can bite humans if handled or accidentally confined against the skin; bites that do occur should be promptly treated to prevent bacterial infection.
1 Araneae: Eutichuridae
B. Funnel weaver web in juniper shrub. WHITNEY CRANSHAW
C. Funnel weaver in funnel retreat of web. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. Agelenopsis species funnel weaver, male. WHITNEY CRANSHAW
E. Sac spider female. WHITNEY CRANSHAW
F. Sac spider male. DAVID SHETLAR
CELLAR SPIDERS1
As their name implies, these spiders often reside in dark, undisturbed locations like cellars, unused basements, and storage sheds. They have very long legs and small bodies, are often confused with daddy longlegs, but these true spiders hang out in tangled webs of silk. An unusual habit of the females is to carry their egg sac in their jaws until the eggs hatch. Cellar spiders feed primarily on other spiders. Despite the common rumors in some regions (especially the Pacific Northwest), cellar spiders are harmless with fangs too small to pierce skin and an absence of venom with hazards to humans.
1 Araneae: Pholcidae
BROWN OR RECLUSE SPIDERS1
These are generally small to medium spiders that are light brown in color, have long legs, and appear to be hairless though their bodies are covered with dense, short hairs. The BROWN RECLUSE (Loxosceles reclusa) has a native range of Kansas and Missouri down to Mexico, but it has been spread through movement of infested furniture and household goods to many other locations. This species is not well adapted to extremely cold or wet habitats. An imported species, the MEDITERRANEAN RECLUSE (L. rufescens) has been introduced into the U.S. and is now quite broadly distributed, although it is almost always found in dark areas of large buildings and occurs only rarely outdoors.
An adult brown spider usually has a leg-span the size of a quarter. Outdoors, brown recluse spiders make thin, sticky, sheetlike tangle webs, usually under the bark of dead trees, spaces under stones, or between pieces of firewood. Inside buildings, they prefer to make webs along the floor of an undisturbed area. The uniformly colored brown abdomen and absence of any banding on the legs is one way to distinguish these spiders from some for which they are commonly mistaken, such as funnel weavers (Agelenidae family).
Adult spiders are capable of piercing human skin, and their venom may cause a local lesion. More extensive tissue damage develops from the effects of the venom in a very small percentage of cases. When this occurs, damage can be extensive because of slow-healing ulcerations that may result in serious scarring and, in very rare instance, have more systemic effects that can be life threatening. As with wounds by other insects and spiders that break the skin, these areas are also susceptible to secondary bacterial infections, so brown recluse bites (and bites of any spider or insect that breaks the skin) should be immediately cleaned and disinfected.
1 Araneae: Sicariidae
DADDY LONGLEGS/HARVESTMEN1
DADDY LONGLEGS are distant relatives of spiders and are classed in their own order, Opiliones. More than 200 species occur in North America, including several common species of European origin. Leiobunum species and Phalangium opilio are usually the daddy longlegs most commonly encountered in gardens.
Like other arachnids, the daddy longlegs have 4 pairs of legs, but the cephalothorax and abdomen are broadly joined (spiders have a “waist” between the cephalothorax and abdomen). However, the legs are usually extremely long, proportionately longer and more conspicuous than with any other animal. Males, although somewhat smaller-bodied than females, have particularly long legs. The body is generally globular and lacks distinct body regions, although the abdomen is clearly segmented. Daddy longlegs have two small eyes mounted on tubercules of the head.
B. Brown recluse spider female. DAVID SHETLAR
C. Brown recluse spiders caught on sticky trap. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. Phalangium opilio feeding on ant. DAVID SHETLAR
E. Leiobunum species of daddy long legs. WHITNEY CRANSHAW
Their jaws (chelicerae) are designed to tear food apart so it can be mixed with digestive fluids. Unlike spiders they do not possess poison glands, although their purported toxicity is a very widespread (worldwide)—and baseless—urban legend. Daddy longlegs also have no glands to produce silk.
Daddy longlegs are generalists in their feeding habits. They may consume small, soft-bodied insects, slugs, and mites and are generally considered beneficial in their effects within a garden. They also scavenge dead insects, spiders, and earthworms. Some may also feed on plant juices, but do not produce significant plant injuries. Most have a 1-year life cycle, with adults maturing late in the season, a habit leading to the other common name “harvestmen.” However, the life cycle of others, including the ubiquitous Phalanigum opilio, may not be as synchronized, so both reproductinve adults and immature stages may be present through much of the growing season.
Occasionally large groups of daddy longlegs will mass together in protected areas (on tree trunks, sides of buildings, etc.), a behavior that seems to help provide collective protection from predators.
1 Opiliones: Phalangiidae, Sclorsomatidae, Laniatores, and others
PREDATORY MITES1
Many types of mites are predators of plant-feeding spider mites. Typically, predatory mites are pear-shaped and have shinier bodies than spider mites. They are also considerably more active and can usually be detected by being considerably faster-moving than their prey. Most predatory mites are generalist predators and may feed on eriophyid mites, thrips, and eggs of insects. Pollen is also important in the diet of some predatory mites. Predatory mites can often provide good control of spider mites but tend to require higher humidity than spider mites. They are often very susceptible to insecticides, which they can pick up by contacting residues on plant surfaces, taking water from plants, or eating contaminated pollen. In most landscapes and gardens, predatory mites can be conserved by treating only plants with pest populations that need quick knockdown (no general cover sprays) or using insecticides that have minimal impact on predatory mites.
Phytoseiidae is the largest family of predatory mites with representatives worldwide. The family includes several species reared and sold for biological control of mites and thrips. Typhlodromus pyri is often found on fruit and ornamental trees and survives well in northern climates. Females overwinter in crevices on trunks and branches. On warm spring days, these adults emerge to begin their search for eggs and spider mites, but they can survive by feeding on pollen, fungi, and plant fluids. Normally, there are three to four generations each summer. Amblyseius fallacius is another common species that survives better in more moderate zones. This species as well as other Amblyseius are commonly sold for spider mite and thrips control in greenhouses, small fruit crops, vegetables, and ornamental plants. (Each species of Amblyseius may have different temperature and humidity tolerances, so check with commercial suppliers to determine the species best suited for your needs.) Phytoselius persimilis is one of the most commonly sold species, but it is a tropical species best suited for high humidity and moderate temperature locations such as greenhouses. The WESTERN PREDATORY MITE, Galendromus (=Typhlodromus) occidentalis, is a native of the western U.S. but it has been spread widely through commerce. It is capable of surviving a wide range of temperatures, can survive most winters, and often will have 8–10 generations in a season. Perhaps the most active mites one might observe on a plant are WHIRLIGIG MITES (Anystidae family). Compared to the phytoseiid mites and spider mites, these are fairly large and often reddish or orange. They can run extremely rapidly in erratic, spiraling patterns. The whirligig mites are generalist predators that usually feed on spider mites or thrips.
Bdellid mites (Bdellidae family) are often called SNOUT MITES because they have elongated mouthparts that project forward. They are relatively common in soils, in leaf litter, and on plants, where they prey on a variety of other mites and small insects. Camerobiid mites (Camerobiidae family) are usually round in body shape with long legs often held straight out from the body. These are swift-moving mites that are often red or orange in color. Both mites are relatively common in landscapes but not usually reared for sale.
A rather unusual group of mites are the VELVET MITES. These live in or on the soil, and young stages of many are parasites of insects. Young stages of some in this family (Trombiculidae) are parasites of other animals and known as chiggers. Adults are general predators that feed primarily on insect eggs. Their reddish color, often bright red, attracts attention, although velvet mites are never very abundant around a garden.
A closely related family of mites, Erythraeidae, contains a subfamily Balaustiinae of large red mites commonly known as “concrete mites.” BALAUSTIUM MITES have lost their parasitic habits and feed primarily on pollen. They can cover sidewalks, fence posts, and sides of buildings in late spring. They will stain light-colored clothing if crushed, so they can become a nuisance issue. Sometimes they are mistaken for a type of chigger, but balaustium mites are not known to bite humans.
1 Acari: Phytoseiidae, Anystidae, Bdellidae, Camerobiidae and others
A. Predatory mite Amblyseius fallacius feeding on spider mite. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
B. Western predatory mite Galendromus occidentalis feeding on spider mite. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
C. Whirligig mite, Anystis agilis. HAROLD J. LARSEN, COLORADO STATE UNIVERSITY
D. Whirligig mite. DAVID SHETLAR
E. Bdellid mite. TOM MURRAY
F. Velvet mite. DAVID SHETLAR
G. Balaustium mite. DAVID SHETLAR
All centipedes develop as predators of other arthropods. They are rarely abundant enough to have much effect on insect populations but feed on a wide variety of potential pests that spend part of their lives in or on the soil surface. The most common centipedes found in yards and gardens are the STONE CENTIPEDES,1 usually about 1 inch long, red-brown in color, and possessing 15 pairs of legs. The largest centipedes are “bark centipedes” of the genus Scolopendra2 which possess 21–23 pairs of legs. Some Scolopendra species that occur in the southern U.S. can be 6 inches in length, and almost all are large enough to produce a very painful bite if handled carelessly.
When digging or moving stones and landscape timbers, one often finds SOIL CENTIPEDES.3 These centipedes are very slim, generally yellowish in color and have more than 29 pairs of legs. These are blind and their fangs are too small to pierce human skin.
The HOUSE CENTIPEDE (Scutigera coleoptrata)4 is a centipede of rather bizarre appearance with extremely long legs, 15 pair on the adults. It is one of the few centipedes adapted to living and reproducing within buildings, where it feeds on spiders, cockroaches, and other indoor insects. However, it is more common (although less commonly seen) outdoors. Outside, these centipedes forage at night and may be noticed around lights that attract other insects. This species will readily self-amputate legs that are grabbed or stuck, but it can immediately alter its walk to compensate for the loss of an appendage and still be capable of rapid escape.
1 Chilopoda: Lithobiomorpha
2 Chilopoda: Scolopendromorpha
3 Chilopoda: Geophilomorpha
4 Chilopoda: Scutigeromorpha
PREDATORY SNAILS
A few snails are primarily predatory, feeding on soft-bodied invertebrates (slugs, snails, earthworms). The best known is DECOLLATE SNAIL (Rumina decollata)1, a Mediterranean species that has been introduced into North America and feeds on the brown garden snail. Euglandina rosae2, known as ROSY WOLFSNAIL or ROSY PREDATOR SNAIL, has been introduced into some areas to control the giant African snail; in Hawaii it is considered to be an invasive species as it has led to the extermination of many native tree snails.
1 Gastropoda: Subulinidae
2 Gastropoda: Spiraxidae
B. Ground centipede. DAVID SHETLAR
C. Centipede tending eggs. DAVID SHETLAR
D. House centipede. JIM KALISCH, UNIVERSITY OF NEBRASKA
E. A large scolopendrid centipede, Scolopendra polymorpha. WHITNEY CRANSHAW
F. Decollate snail. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA IPM PROGRAM
Many wasps and ants are predators of other arthropods. In these insects the adult is the predatory stage, often collecting insect prey to feed their developing young. Ants and the various paper-nesting wasps are social insects. These produce a colony and different individuals may have specialized tasks, with usually a single queen the sole reproducing form. Other wasps are solitary and the female does all tasks involved in prey capture, nest construction and rearing of young.
PREDATORY ANTS1
A wide variety of habits exist among the hundreds of species of ants found in North America. Some are considered pests because they occur in nuisance numbers in homes, nest in wood, or damage plants. Many are important predators of insect pests, particularly in sites such as turfgrass; several are largely predaceous, or eat insects as part of their diet. FIRE ANTS (Solenopsis species) (page 518), found in the southern U.S., are largely predatory and may devastate insect populations that occur in the vicinity of nests. GHOST ANT (Tapinoma melanocephalum) has been found to feed on spider mites and many types of insects and has been considered as a useful biological control species in greenhouses. Many of the other common ants found in and around yards and gardens, such as FIELD ANTS (Formica species), CARPENTER ANTS (Camponotus species), and PAVEMENT ANTS (Tetramorium caespitum), feed on both living and dead insects as well as on sweet materials such as honeydew.
1 Hymenoptera: Formicidae
PAPER WASPS1
Paper wasps annually make open-celled paper nests that are not covered with a papery envelope. They are usually observed hanging from eaves and the ceilings of outbuildings, but they may also nest in aboveground hollows and along the branches of trees and shrubs. The great majority of those found in North America are in the genus Polistes. In addition to native species, a recently introduced species, now widely established in North America, is the EUROPEAN PAPER WASP, Polistes dominula. East of the Rocky Mountains, P. annularis is a common red-brown species with a black abdomen that has a single yellow band. This species can make nests that contain 1,000 or more individuals by the end of the summer. P. exclamans, P. fuscatus (NORTHERN PAPER WASP), and P. dorsalis are common species that are usually more brightly colored with red, brown, and yellow markings.
In areas of western North America, the YELLOWLEGGED PAPER WASP (Mischocyttarus flavitarsis) may be common. In the southern states, Mischocyttarus mexicanus commonly makes small nests in rolled plant leaves or under the protection of palm leaves. Both these species are somewhat smaller than Polistes wasps and have a distinctively narrow first segment of the abdomen.
All the paper wasps rear their young on chewed-up insects. They are commonly seen searching plants for caterpillars, beetle larvae, and other suitable prey, which are then chewed and fed to the grublike larvae within the nest. Paper wasps are very valuable in the biological control of many pest insects in yards and gardens. Paper wasps can sting, and some species will aggressively defend the nest; however, unlike yellowjackets, they do not scavenge at foods.
1 Hymenoptera: Vespidae
B. Red imported fire ants preying on mole cricket. DAVID SHETLAR
C. Ghost ants. DAVID SHETLAR
D. Carpenter ant feeding on small fly. WHITNEY CRANSHAW
E. Polistes paper wasp feeding on cutworm. DAVID SHETLAR
F. Nest of Polistes dorsalis. DAVID SHETLAR
G. Northern paper wasp chewing on fence to collect wood fibers. DAVID SHETLAR
H. European paper wasp feeding on cabbagworm. WHITNEY CRANSHAW
I. Nest of the European paper wasp. JIM KALISCH, UNIVERSITY OF NEBRASKA
J. Yellowlegged paper wasp at nest. WHITNEY CRANSHAW
HORNETS AND YELLOWJACKETS1
The BALDFACED HORNET (Dolichovespula maculata) and AERIAL YELLOWJACKET (D. maculata) create large aerial nests covered with a papery shell, produced from chewing on weathered wood or cardboard. These nests are produced annually, started by a single fertilized female (queen) in late spring and then abandoned at the end of the season. Both these insects rear their young strictly on a diet of living insects, particularly caterpillars. Although they sting if the nest is disturbed, the activities of these insects are largely beneficial to gardeners because of their importance as biological control agents.
Of far more mixed effects are the activities of YELLOWJACKETS (Vespula species) (page 586). Some species are primarily predators, such as the PRAIRIE YELLOWJACKET (V. atripilosa), which feeds largely on flies, but the majority of North American yellowjackets have much broader food choices, and most are scavengers that frequently visit outdoor dining areas and trash cans. These types of yellowjackets, which include the GERMAN YELLOWJACKET (V. germanica), WESTERN YELLOWJACKET (V. pensylvanica), and EASTERN YELLOWJACKET (V. maculifrons), may feed on some live insects, but more often will consume dead insects and earthworms and scavenge carrion—and feed on meaty foods laid out by humans. They also forage on sweet materials, particularly late in the season, and can be serious nuisance pests during outdoor dining. As yellowjackets are the predominant stinging insect in much of North America, often forage as scavengers rather than as predators, and are not significant pollinators, yellowjackets are usually considered undesirable around the garden.
Yellowjackets make paper nests that include multiple layers of cells and are covered with a paper envelope, in the manner of the Dolichovespula species; however, the nests are always hidden, often belowground. Normally all the hornets and yellowjackets abandon their nests upon the arrival of cold winter temperatures; on rare occasions, nests of the SOUTHERN YELLOWJACKET, V. squamosa, can persist more than one season in warmer areas of the southern U.S. Only newly emerged, mated females can survive freezing temperatures, and these build new nests the following spring. These wasps do not reoccupy old nests, a habit that allows them to avoid persistent pathogens and parasites. Once a hard freeze has occurred, old nests can be removed and potential nesting cavities sealed to prevent future colonization of these areas.
The EUROPEAN HORNET (Vespa crabro germana) (page 588) is an introduced species often twice the size of the baldfaced hornets and three times the size of yellowjackets. This is a relatively nonaggressive species that feeds primarily on captured insects, but the workers are known to chew the bark off tree and shrub branches. They will often return to these plant wounds to lick up exuding sap. It prefers to nest in hollow logs but will build nests in building attics and other voids.
1 Hymenoptera: Vespidae
POTTER WASPS1
The potter wasps are related to the yellowjackets and paper wasps but do not produce colonies but instead construct mud nests for rearing young. Those in the genus Eumenes produce nest cells in the form of clay pots they provision with paralyzed caterpillars and beetle larvae. A single wasp larva develops within each of the nest cells. The potter wasps are nonaggressive and rarely sting.
1 Hymenoptera: Vespidae (Eumeninae)
B. Baldfaced hornet. DAVID SHETLAR
C. Prairie yellowjacket, a predatory species that often feeds on flies. WHITNEY CRANSHAW
D. Yellowjacket nest entrance on ground. DAVID SHETLAR
E. Western yellowjacket feeding on cabbageworm. WHITNEY CRANSHAW
F. Western yellowjacket scavenging on meat. WHITNEY CRANSHAW
G. Large nest of eastern yellowjacket established among hay bales. TERRY S. PRICE, GEORGIA FORESTRY COMMISSION, BUGWOOD.ORG
H. European hornets. JIM BAKER, NORTH CAROLINA STATE UNIVERSITY, BUGWOOD.ORG
I. Potter wasp larva extracted from nest cell. WHITNEY CRANSHAW
J. Potter wasp bringing caterpillar prey to nest. JON YUSCHOCK, BUGWOOD.ORG
The hunting wasps are solitary wasps and do not produce a colony like those of the social wasps (paper wasps, yellowjackets, hornets). Instead the females construct an entire nest and do all the foraging needed to feed their young, working alone. Nearly a thousand species of these wasps occur in North America, but only a few are commonly noticed. Depending on species, some hunting wasps make nests in soil in the form of a burrow connected to underground chambers. Others excavate tunnels in the pith of plants or utilize holes made by wood-boring insects that have emerged from tree trunks or logs. A few create nest cells out of mud.
Each type of hunting wasp specializes in a different kind of host insect. The largest of the hunting wasps are the CICADA KILLERS (Sphecius spp.)2 that specialize in the large dog-day cicadas (page 408). Cicada killers dig large underground nests that may penetrate well below a foot and result in conspicuous mounds. Many other hunting wasps nest in the soil, such as Ammophila spp.,1 which specialize in hairless caterpillars such as hornworms and cutworms, Podalonia spp.,1 which target cutworms and other caterpillars in the family Noctuidae, Bembix spp., which specialize in flies, and Cerceris spp.,2 which collect weevils and wood-boring beetles.
Bembix pruinosa returning to ground nest with horse fly prey. HOWARD ENSIGN EVANS
Various orthopterans are the prey of some of the common hunting wasps. Katydids and crickets are prey used by the Sphex species,1 which are large wasps that include the GREAT GOLDEN DIGGER WASP (S. ichneumoneus) and S. pensylvanicus. Grasshoppers are the prey of most Prionyx spp.,1 field crickets (Gryllus spp.) of the STEEL-BLUE CRICKET HUNTER (Chlorion aerarium),1 and tree crickets (Oecanthus spp.) of the GRASS-CARRYING WASPS of the genus Isodontia.1 Most of these make nests in the soil, but the last use existing cavities aboveground such as those left by wood borers. The grass-carrying wasps use grass to separate the rearing chambers, and it is not uncommon for them to use the crevices present in the sash tracks of windows, lending them the name “window wasps.”
Several small hunting wasps that prey on insects such as aphids, psyllids, and leafhoppers use small cavities in plants for nest sites. Pemphredon spp.2 that hunt aphids excavate cavities from the pith of plants such as rose and caneberries. Passaloecus spp.2 often use preexisting cavities, including predrilled blocks used to attract cavity-nesting bees.
Two kinds of hunting wasps, known as “mud daubers” fully form nest cells using mud. The BLACK-AND-YELLOW MUD DAUBER (Sceliphron caementarium)1 is found throughout North America and makes a series of cylindrical cells under eaves and in other sites protected from rainfall. Considerably longer mud nest cells are produced by the ORGANPIPE MUD DAUBER (Trypoxylon politum),2 which occurs in eastern North America, extending to Texas. Both these wasps use spiders as prey, often packing each cell with a dozen or more paralyzed spiders that are quickly consumed by their larvae.
Despite their often fearsome appearance, the hunting wasps rarely sting and do not possess venom that causes pain on par with the social wasps (e.g., paper wasps, yellowjackets).
1 Hymenoptera: Sphecidae
2 Hymenoptera: Crabronidae
B. Cicada killer returning to nest with prey. DAVID SHETLAR
C. Great golden digger wasp. DAVID SHETLAR
D. An Ammophila species hunting wasp with caterpillar prey. DAVID CUPPAERT, BUGWOOD.ORG
E. Grass carrier wasp with tree cricket prey. JOHNNY N. DELL, BUGWOOD.ORG
F. Debris excavated from nests of grass carrying wasps. JIM KALISCH, UNIVERSITY OF NEBRASKA
G. Pemphredon wasp resting on leaf. WHITNEY CRANSHAW
H. Black-and-yellow mud dauber constructing nest. HOWARD ENSIGN EVANS.
I. Organpipe mud dauber returning to nest. DAVID SHETLAR
J. Nest cell of black-and-yellow mud dauber opened to expose spider prey. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
SPIDER WASPS1
The spider wasps are also hunting wasps of solitary habit. All specialize in spiders, choosing hosts that are larger than the wasp. The spiders are incapacitated by a sting, then dragged to a tunnel in the soil, which the wasp either finds (i.e., the burrow of the spider) or constructs. The host spider is then cached in the nest and an egg laid on it. Upon egg hatch, the spider wasp larva rapidly consumes the immobilized spider.
Adult spider wasps are fairly common at flowers feeding on nectar and pollen. Spider wasps are capable of producing a painful sting, but they are not aggressive species and sting only if handled.
1 Hymenoptera: Pompilidae
INSECT PARASITOIDS
Many wasps and some flies develop as parasitoids. With these insects the adult female seeks insects that are appropriate hosts to support her young then lays an egg in or on the insect. As the parasitoid larva develops, it feeds initially on nonvital tissue, and the insect host may show no external evidence of the parasite; however, as the parasitoid larva matures it ultimately does kill the insect on which it develops. Most parasitoid larvae develop inside their host (endoparasitoids). A few, notably in the wasp family Eulophidae, may pass through stages that feed from the outside of the host (ectoparasitoids). However, larvae of many parasitoids emerge from the host when feeding is completed and pupate on the outside. Adult stages of insect parasitoids usually feed on nectar, pollen, and honeydew; a few feed on blood of host insects which they acquire by puncturing with their ovipositor.
TIPHIID AND SCOLIID WASPS
These wasps are mostly parasites of white grub larvae. Adult wasps can be fairly large and may superficially resemble yellowjackets or other hunting wasps. Myzinum1 and Tiphia1 are the two most common genera in North America. Scolia dubia2 is more than an inch long and generally black with orange-and--yellow markings on the abdomen. This hairy wasp will persistently hover over turf or garden soil infested with green June beetle (page 468) larvae. Both tiphiid and scoliid wasps dig into the soil, paralyze their prey in the soil, and attach an egg. The wasp larvae remain on the outside of the grub body while the head is buried inside the body.
1 Hymenoptera: Tiphiidae
2 Hymenoptera: Scoliidae
PELECINID WASPS
The pelecinid wasps have only one North American species, Pelecinus polyturator,1 but it is a large black wasp of unusual appearance. The abdomen of the female is extremely elongated, extending an inch and a half, which allows laying eggs in soil. Larvae are parasites of white grubs (scarabs) in soil.
1 Hymenoptera: Pelecinidae
A. Spider wasp with spider prey. DAVID CAPPAERT, BUGWOOD.ORG
B. Spider wasp dragging spider prey. WHITNEY CRANSHAW
C. A Myzinum species of tiphiid wasp. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. A Tiphia species of tiphiid wasp. DAVID SHETLAR
E. Larva of a Tiphia wasp developing on white grub host. DAVID SHETLAR
F. Scoliid wasp Campsomeris pilipes digging in soil in search of host. WHITNEY CRANSHAW
G. A scoliid wasp. DAVID SHETLAR
H. Pelecinid wasp. DAVID SHETLAR
ICHNEUMONID WASPS1
These wasps are medium to fairly large, slender wasps. Antennae are quite long, and the females usually possess a long and conspicuous ovipositor. Ichneumonid wasps are most commonly encountered as parasites of caterpillars. Beetles, sawflies, and other wasps are other hosts. Common genera include Hyposoter, Diadegma, Ophion, and Exochus. The family Ichneumonidae is one of the largest of any insect group, with 3,300 described species in North America.
The largest ichneumon wasps are those in the genus Megarhyssa, which are parasites of horntail larvae, a type of wood-boring sawfly. These giant ichneumon wasps may be 3 inches long, including the very long tail-like ovipositor used to penetrate wood.
1 Hymenoptera: Ichneumonidae
BRACONID WASPS1
Braconids are very similar to ichneumonids but usually much smaller. This large and important family of wasps has more than 1,900 North American species. Bracon, Chelonus, Leiophron, Macrocentrus and Opius are common genera that generally attack caterpillars. The white or yellowish pupae of Cotesia species, spun on or adjacent to their caterpillar host, are among the most commonly observed stages of any parasitic wasp. Braconids are a very diverse group, with some taxonomists elevating the 29 or more subfamilies to family level. There are subfamilies that specialize in parasitizing almost all the other orders of insects.
The aphid parasitoids subfamily (Aphidiinae) are among the most ubiquitous of the smaller braconid wasps, found almost invariably among aphid colonies. As the wasp larva develops within an aphid, the host typically swells, grows lighter in color, and becomes affixed to the leaf. Aphids killed in this manner are often referred to as “aphid mummies.” A circular hole cut in the aphid by the emerging wasp is also characteristic. Among the common genera of aphid wasps are Trioxys, Diaeretiella, Lysiphlebus, and Aphidius.
The giant ichneumon wasp Megarhyssa macrurus, a parasitoid of pigeon tremex larvae. DAVID SHETLAR
Adult braconid wasps emerged from woollybear host. JIM KALISCH, UNIVERSITY OF NEBRASKA
1 Hymenoptera: Braconidae
A. Ichneumonid wasp, Itoplectis conquisitor, ovipositing into caterpillar hosts. GERALD J. LENHARD, LOUISIANA STATE UNIVERSITY, BUGWOOD.ORG
B. Ichneumonid wasp ovipositing into fall webworm caterpillars. DAVID SHETLAR
C. Megarhyssa atrata ovipositing into trunk for horntail host. DAVID SHETLAR
D. A braconid wasp, Aleiodes indiscretus, oviposiiting into gypsy moth larva. SCOTT BAUER, USDA AGRICULTURAL RESEARCH SERVICE
E. Cocoons of Cotesia glomeratus, a braconid wasp parasitoid of imported cabbageworm. WHITNEY CRANSHAW
F. Braconid wasp larvae exiting host caterpillar. JIM KALISCH, UNIVERSITY OF NEBRASKA
G. Cocoons of Cotesia congregata on back of tobacco hornworm host. DAVID SHETLAR
H. Cotesia congregata adult, with cocoons of pupae on caterpillar host. DAVID SHETLAR
I. Pupal cocoon of Dinocampus coccinellae, a parasitoid of lady beetles. DAVID SHETLAR
J. Aphid parasitoid ovipositing. DAVID SHETLAR
K. Potato aphid “mummies” showing evidence of parasitism by a braconid wasp. JIM KALISCH, UNIVERSITY OF NEBRASKA
CHALCID WASPS1
Known as chalcid wasps, this superfamily (Chalcidoidea) contains more than a dozen families that are generally tiny parasitic wasps. Many are small enough to parasitize insect eggs, but insect nymphs, larvae, or pupae can also be attacked. Many species of chalcids have been introduced as biological control agents of introduced scale, caterpillar, beetle, and fly pests.
The PTEROMALID WASPS (Pteromalidae family) include species that are very important parasites of sawflies. Another group are those that develop on larvae and pupae of various filth-breeding flies, some of which are sold commercially as “fly predators” or “fly parasites” to control nuisance flies around livestock operations. Pteromalus, Perilampus, Spalangia, and Nasonia are among the genera of pteromalid wasps most important for biological control of pest species.
A pteromalid wasp ovipositing into a fly pupa. USDA ARS PHOTO UNIT, USDA AGRICULTURAL RESEARCH SERVICE, BUGWOOD.ORG
ENCYRTID WASPS (Encyrtidae family) are very small wasps that develop internally in eggs, larvae, or pupae of certain insects. The genera Anagyrus, Leptomastix, and Metaphycus include species that serve as important natural enemies of some of the most common mealybugs and soft scales. An unusual species is Copidosoma truncatellum, which lays its eggs in the eggs of cutworms, loopers, and other caterpillars. The species is polyembryonic, and numerous larvae—sometimes more than 1,000—develop from the few eggs originally laid. The larvae of this wasp develop throughout the larval life of the caterpillar host, killing it as it prepares to pupate.
APHELINID WASPS (Aphelinindae family) include many important species that attack insects in the order Hemiptera. Several Encarsia species are very important as parasites of whiteflies and cause the host nymph to turn black when parasitized. Aphelinus is a genus that includes important parasites of aphids, which also characteristically turn dark black when parasitized. Coccophagus and Aphytis include many of the parasites most important in control of scale insects.
Most true CHALCID WASPS (Chalcididae family) are internal parasites of caterpillars, although some develop in fly larvae. They are distinguished by having very enlarged femurs on the hind legs, and are some of the larger wasps in the subfamily, occasionally reaching ⅜ inch in length. Brachymeria is the most common and widespread genus among the chalcid wasps in North America.
The EULOPHID WASPS (Eulophidae family) are very small (typically ca. 
inch) and many develop as external parasites of their hosts. Some of the most conspicuous are species of Euplectrus that develop on the body of several kinds of caterpillars. Others are parasites of scales, psyllids, and flies—including many of the leafmining flies. Some eulophids are egg parasites of beetles.
The smallest parasitic wasps—and smallest insects known—are those that develop as internal parasites of insect eggs. The TRICHOGRAMMA WASPS (Trichogrammatidae family) are well known as parasites of caterpillar eggs, and several species (T. pretiosum, T. platneri, T. brassicae, T. minutum) are widely available for sale as biological control agents. Even more minute are the FAIRYFLIES (Mymaridae family), which include the genus Anagrus, a group that develops in the eggs of leafhoppers and can be important biological controls.
1 Hymenoptera: superfamily Chalcidoidea
A. Cabbage looper larva packed with pupae of a Copidosoma floridanum, an encyrtid wasp. DAVID SHETLAR
B. Encarsia formosa, an aphelinid parasitoid of greenhouse whitefly. DAVID CAPPAERT, BUGWOOD.ORG
C. Greenhouse whiteflies parasitized by Encarsia formosa (dark insects are parasitized). DAVID CAPPAERT, BUGWOOD.ORG
D. A parasitoid of scale insects, Coccophagus species. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
E. Phasnogophora sulcata, a chalcid parasitoid of flatheaded borers. DAVID CAPPAERT, BUGWOOD.ORG
F. Tetrastichus planipennisi, a eulophid wasp introduced to control emerald ash borer. DAVID CAPPAERT, BUGWOOD.ORG
G. Larvae of an ectoparasitic eulophid wasp, Euplectrus species, on back of caterpillar host. DAVID SHETLAR
H. Trichogramma wasp ovipositing in egg of a corn earworm. JACK KELLY CLARK, COURTESY OF UNIVERSITY OF CALIFORNIA STATEWIDE IPM PROGRAM
SARCOPHAGID FLIES1
Most sarcophagid flies feed on fresh carrion and are known as “flesh flies.” Others develop as parasites of insects, including grasshoppers, caterpillars, and beetles, and are sometimes important natural enemies of certain pest insects. For example Sarcophaga aldrichi is one of the most common natural enemies of tent caterpillars. It is sometimes called the “friendly fly” as it will frequently land on people, but it does not bite and is harmless to humans. Grasshoppers are often heavily attacked by sarcophagid flies in the genus Blaesoxipha.
Sarcophagid flies are generally a little larger than a house fly and often have black bodies with gray thoracic stripes. Many have prominent red-orange eyes, and the egg-laying structures on the tip of the abdomen may also be red-orange, hence other common names of these insects are “red-eyed” or “red-tailed flies.”
1 Diptera: Sarcophagidae
TACHINID FLIES1
The tachinid flies are a large and very important family of parasitic flies with about 1,300 North American species. All develop as internal parasites of other insects, including many caterpillars, beetles, true bugs, earwigs, and grasshoppers that occur as garden pests. Typical species somewhat resemble house flies but tend to have more stout, bristly hairs on the abdomen. Females usually glue an egg to the body of a host, often near the head, and the maggot larva burrows into the host’s body cavity. However, some tachinid flies insert larvae directly into the host insect, whereas others lay tiny eggs on foliage that hatch when ingested.
Tachinid fly laying eggs on walnut caterpillar. JIM KALISCH, UNIVERSITY OF NEBRASKA
Tachinid fly larvae emerged from pupa of a cecropia moth. JIM KALISCH, UNIVERSITY OF NEBRASKA
1 Diptera: Tachinidae
B. A Blaesoxipha species of sarcophagid fly, parasitoid of grasshoppers. WHITNEY CRANSHAW
C. Tachinid fly ovipositing on yellownecked caterpillar. DAVID SHETLAR
D. Squash bugs with attached eggs of a Trichopoda species of tachinid fly. WHITNEY CRANSHAW
E. Adult of a Trichopoda species of tachinid fly. JIM KALISCH, UNIVERSITY OF NEBRASKA
F. Eggs of the tachinid fly Istocheta aldrichi laid on Japanese beetle. JIM KALISCH, UNIVERSITY OF NEBRASKA
G. Cabbage looper showing evidence of parasitism by developing tachinid flies (dark spots are breathing tubes of parasitoid larvae). WHITNEY CRANSHAW
H. Pupa of a tachinid fly parasitoid of European earwig. WHITNEY CRANSHAW
Although infrequently observed, insects and mites often suffer from infection by pathogens, many of which produce lethal diseases. Certain kinds of fungi, bacteria, protozoa, and viruses can all kill insects, and many are important in their management.
Viruses that produce disease in insects are most evident among the caterpillars and sawflies. One particularly gruesome group of insect viruses (nuclear polyhedrosis viruses/NPV) cause wilt disease. Caterpillars and sawflies infected by these viruses are killed rapidly, their virus-filled bodies hanging limply by their prolegs. At the slightest touch, the insects rupture, spilling the virus particles onto leaves below them to infect other insects. Wilt diseases are important biological controls of several caterpillars, including cabbage looper, gypsy moth, and Douglas-fir tussock moth.
Other types of viruses, known as granulosis viruses, act considerably more slowly. These other viruses may produce only modest external symptoms such as a chalky color of the infected insect or a general listlessness. A few of these have been commercially developed, including viruses that affect codling moth (Cyd-X®, Madex®) and corn earworm (Gemstar®).
Several types of bacteria may infect insects and typically enter through the digestive system. Larvae of Japanese beetle are susceptible to Paenibacillus popilliae, producing milky disease that causes infected grubs to turn creamy white, grow poorly and often die. Related species infect other species of white grubs. An extremely infectious and potentially devastating disease of larval honey bees is American foulbrood, produced by Paenibacillus larvae. Various Serratia species also cause infections in many insects.
Bacteria may also produce various toxins that can be lethal to insects. Bacillus thuringiensis (Bt) is the best known of these, capable of producing protein crystals that can destroy cells of the digestive system of susceptible species. A great many strains of this bacterium have been discovered, each of which produces compounds that affect insects differently. Several strains have been commercialized and are variously used to control certain caterpillars (kurstaki, aizawi strains), leaf beetle larvae (tenebrionis strain), larvae of mosquitoes, fungus gnats, and related flies (israelensis strain), and white grubs (galleriae strain).
Alfalfa webworms killed by Bacillus thuringiensis. JOHN CAPINERA, UNIVERSITY OF FLORIDA
Fungi produce some of the more spectacular diseases of insects. A wide variety of insects succumb to fungus disease around the yard and garden. Fungus-killed insects and mites become stiff and, when conditions are right, covered with a white, light green, or pink “fuzz”—the spores of the fungus. Perhaps the fungal disease of insects most commonly encountered in a garden is Entomophthora muscae that infects various root maggot flies. Infected flies die stuck to the tops of plants and at other high points around the garden. This fungus can also infect house and blow flies, which may be seen stuck onto windows surrounded by a halo of spores. Grasshoppers infected with strains of E. grylli may be seen attached to upper stems of plants, where they die, stiffly clinging to the plant. Entomophaga maimaiga is an introduced fungus that produces devastating outbreaks among gypsy moth when spring moisture conditions are optimal for its spread and infection.
A. Gypsy moth larva killed by a nuclear polyhedrosis virus wilt disease. JOHN GHENT, JOHN GHENT, BUGWOOD.ORG
B. Sawfly larvae killed by a nuclear polyhedrosis virus. STEVEN KATOVICH, BUGWOOD.ORG
C. Masked chafer grub showing evidence of infection with a milky disease bacterium (on right). DAVID SHETLAR
D. Japanese beetle grub (on left) showing evidence of infection with a Serratia species of bacterium producing amber disease. DAVID SHETLAR
E. Seedcorn maggot flies killed by the fungus Entomophthora muscae. WHITNEY CRANSHAW
F. Gypsy moth larva killed by the fungus Entomophaga maimaiga. DAVID SHETLAR
Beauveria bassiana is a very common fungal pathogen of many insects and also currently marketed for insect control in yards, gardens, and greenhouses. It produces white muscardine disease, which can cover infected insects with snow-white spores. Another common fungal pathogen of many insects is Metarhizium anisopliae, producing green muscardine disease, referring to the olive-green spores produced by this fungus. Several other fungi infect insects, some of which are also commercially developed, including Isaria fumosorosea and Lecanacillium lecanii.
Microsporidia, a type of fungi, tend to cause debilitating infections among insects. Effects are often subtle, such as reduced feeding, activity, or reproduction. Immature stages are usually much more susceptible to infections and survival can be reduced. Spruce budworms and grasshoppers are among the groups of insects that are common hosts of microsporidia parasites. Several Nosema species of microsporidia are also important parasites of honey bees and bumble bees. Nosema locustae can infect developing grasshoppers and is commercially developed for grasshopper control.
Many kinds of nematodes develop as parasites of insects. One diverse group are the mermithid nematodes that develop as internal parasites. They may develop slowly in their host, causing debilitating disease that is ultimately lethal. Mermithid nematodes are common in many beetles, mosquito larvae, and some grasshoppers. The largest of the mermithid nematodes one might encounter in a garden is Mermis nigrescens, a parasite of grasshoppers that can be more than 3 inches long.
Other nematodes are better described as entomopathogenic nematodes because of their involvement with bacteria. These nematodes always carry insect-killing bacteria with which they have mutual interdependence. The nematodes actively penetrate the body of some insect host, either through natural openings (mouth, spiracles, anus) or by cutting through the exoskeleton. They release the bacteria upon penetration and the bacteria then grow rapidly in the blood (hemolymph) of the insect, killing it within hours to a few days. The nematodes develop on the resulting soup of bacteria and degraded insect tissue.
Two genera of entomopathogenic nematodes have been developed as biological controls for insect pests. Various Steinernema species (all contain Xenorhabdus bacteria species) are used to manage insects, including certain caterpillars, fungus gnats, and mole crickets. Infected insects turn tan or gray in color. Heterorhabditis species (all contain Photorhabdus bacteria species) tend to be more effective for control of larvae of white grubs and root weevils in soil. Infected insects turn a red-brown color. Heterorhabditus nematodes are also capable of direct penetration through the host exoskeleton.
Another group of large wormlike parasites that affect insects are the horsehair worms. These are placed in a separate phylum from the nematodes (Nematomorpha) and are thicker and darker than Mermis nigrescens, the common nematode parasite of grasshoppers. Horsehair worms have a wider host range and can affect many insects—various crickets and beetles perhaps most commonly. Several species in the genus Gordius may come to the attention of gardeners, particularly near water sources. Eggs of horsehair worms are laid in water, where they hatch. The larvae attach to plants growing in the water and infect insects that ingest them while eating the plants. Subsequently, infections may move to predators that feed on the originally infected insect, such as a ground beetle or mantid that consumes an infected cricket. After the horsehair worm has completed development within the insect host, infected insects ultimately move to water where the mature parasites emerge, then lay eggs. Their occurrence in animal watering troughs is the basis for the common name horsehair worm, as they have a general appearance of an animated horse’s hair.
B. Billbug adult killed by the fungus Beauveria bassiana. DAVID SHETLAR
C. Pea aphid killed by a fungus. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. Mermis nigrescens, the grasshopper nematode. JOHN CAPINERA, UNIVERSITY OF FLORIDA
E. A horsehair worm. WHITNEY CRANSHAW
F. Masked chafer grub killed by a Heterorhabditis species of nematode. DAVID SHETLAR
More than 4,000 species of bees are native to North America, and a great many of these may visit garden plantings. All rear their young on pollen and nectar, and many have evolved close relationships with the plants that provide these foods, and the bees providing essential pollination services in return.
Most familiar are the bees that form colonies: the honey bee and the bumble bees. These are also truly social insects, which have overlapping generations, provide cooperative care of the young, and divide labor between distinct castes (fertile female queen, sterile female workers, male drones); however, the overwhelming majority of bees are solitary, with all provisioning and care of the young handled by the mother.
Bees do possess a stinger, a special modification of the ovipositor—used to lay eggs in other insects—that is linked to venom glands. (Some ants and wasps also have a stinger, and the great majority of insect stings are produced by these insects, including fire ants, yellowjackets, and paper wasps). Bees will sting in defense, usually defense of the colony, and the sting of the social bees can be painful. Solitary bees sting only if handled or accidentally crushed against the skin, and their sting is much less painful. Male bees do not possess a stinger and thus cannot sting, although they may engage in aggressive bluffing behaviors to defend territory.
HONEY BEE
The HONEY BEE (Apis mellifera)1 is an insect native to parts of Eurasia and Africa that was introduced into North America early, during European colonization in the 1620s. It is an excellent pollinator of many crops and is particularly important for pollinating tree fruits; pollen they return to the hive is carried in special pollen baskets (scopae) on the hind legs. Honey bees also produce large amounts of honey for use as an energy source, and the excess is collected by beekeepers. Honey bees construct nest cells of wax, produced as flakes from special glands on the abdomen, and beeswax is also an important commercial product.
Unlike other bees that occur in North America, honey bees maintain perennial colonies. They survive over the winter with an intact colony numbering in the thousands, with the bees clustering together for warmth, feeding on the stored honey and pollen collected the previous season. Although egg laying is suspended for most of the winter months, the queen resumes egg laying in late winter, increasing the population to take full advantage of the nectar flow that comes with spring flowers.
At no point can an individual honey bee survive long on its own, and a honey bee colony can be considered a superorganism that functions as a collective unit of all members. Although the fertilized female queen produces eggs, new colonies form when the colony divides through a swarming event. During swarming the majority of the worker bees and the old queen leave the colony and seek to establish a colony in a new location. The workers that remain behind rear a new queen that, after mating, will resume egg laying.
Honey bees are nonaggressive when foraging and rarely sting unless their hive is disturbed or they are accidentally trapped or handled. (The great majority of “bee stings” result from the activity of very different insects, usually yellowjacket wasps.) The stinger of worker honey bees is barbed and is pulled out of the bee’s body in the act of stinging, resulting in the bee’s death.
1 Hymenoptera: Apidae
A. Honey bee collecting pollen. SUSAN ELLIS, BUGWOOD.ORG
B. A honey bee strain of dark coloration. DAVID SHETLAR
C. Honey bee queen being tended by workers in a colony. JESSICA LOUQUE, SMITHERS VISCIENT, BUGWOOD.ORG
D. Honey bee eggs and young larvae at base of nest cells. JESSICA LOUQUE, SMITHERS VISCIENT, BUGWOOD.ORG
E. Frame from a honey bee hive showing capped cells containing pupae. WHITNEY CRANSHAW
F. Honey bee swarm. WHITNEY CRANSHAW
Bumble bees (Bombus spp.)1 are large, fuzzy bees brightly colored black with yellow and/or orange. Like honey bees, they are social insects that produce a colony, usually in an abandoned rodent or bird nest where there is insulating material they use to surround the nest. Bumble bee colonies are abandoned at the end of the year, however, and only new, large, fertilized queens survive the winter. The queen establishes a new colony in spring, conducting all chores of foraging, hive construction, and rearing. The first workers produced are usually quite small, but they assist the queen as the colony develops. As the colony grows, worker size tends to increase and some reproductive forms (queens, males) are produced toward the end of the season.
Bumble bees are native insects, with close to 50 species in North America. Many are important pollinators, and they have a unique method of acquiring pollen from some plants, known as buzz pollination, which shakes pollen from some kinds of flowers. The collected pollen is then packed into pollen baskets on the hind legs, in a manner similar to honey bees and others in the family Apidae. Bumble bees are used extensively to pollinate greenhouse-grown tomatoes, and many native plants are dependent on buzz pollination for seed set. Bumble bees sting readily in defense of their hive but are nonaggressive while foraging. The sting is painful, but the stinger is not left behind.
The species of bumble bees one might find in a garden vary with location. Along the Pacific Coast Bombus vosnesenskii (VOSNESENSKY BUMBLE BEE) is common, and in the Pacific Northwest, early in the season, one frequently sees B. melanopygus (BLACKTAIL BUMBLE BEE). In Texas, B. pensylvanicus (AMERICAN BUMBLE BEE) is one of the more common species in gardens, while in the Rocky Mountain west, B. huntii (HUNT BUMBLE BEE) is often observed. Common species in the Mid-Atlantic/New England area include B. impatiens (COMMON EASTERN BUMBLE BEE) and B. bimaculatus (TWOSPOTTED BUMBLE BEE).
1 Hymenoptera: Apidae (Apinae)
LARGE CARPENTER BEES
LARGE CARPENTER BEES (Xylocopa spp.)1 somewhat resemble bumble bees, both in size and in general shape. They can usually be distinguished from bumble bees by having a less hairy abdomen, which often has a metallic blue or green sheen. Large carpenter bees also differ by being a solitary species, although it is common for several nests to be built in close proximity or two females using the same opening. As the name may imply, large carpenter bees typically create nests in wood, which they can tunnel deeply. Dead limbs, logs, and stems of large plants serve as nest sites in natural areas; however, unfinished structural wood, usually coniferous softwoods such as pines, cedar, and juniper, is commonly used by the EASTERN CARPENTER BEE (Xylocopa virginica). Tunneling can be extensive, typically extending 1–1½ feet, going primarily with the grain. The tunnel is then used to create a series of nest cells, each provisioned with nectar and pollen, separated by partitions of chewed wood. Both males and females pack themselves into old burrows to overwinter. Woodpeckers will often peck out these bees from infested wood during the winter.
Females are not aggressive and very rarely have been known to sting; however, the males often make threatening types of flights to defend territory, and these actions often cause alarm. This is purely a bluffing behavior, as the males cannot sting nor will they bite. In addition to this behavior, males of many species, including the eastern carpenter bee, can be identified by a patch of yellow or white hair on the front of the head.
1 Hymenoptera: Apidae (Xylocopinae)
B. Nest of Bombus vagans. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
C. Bumble bee collecting pollen. DAVID SHETLAR
D. Bumble bee, Bombus fraternus. JOHNNY N. DELL, BUGWOOD.ORG
E. Bumble bee, Bombus vosnesenskii. WHITNEY CRANSHAW
F. Carpenter bee at nest entrance. JIM KALISCH, UNIVERSITY OF NEBRASKA
G. Range of size between queen (left) and workers of Bombus huntii. WHITNEY CRANSHAW
H. Carpenter bee leaving nest. DAVID SHETLAR
I. Carpenter bee at flower. SUSAN ELLIS, BUGWOOD.ORG
J. Male carpenter bee showing white facial marking. DAVID SHETLAR
Several kinds of solitary bees nest in cavities, either ones that naturally exist (e.g., old wood borer holes, hollow canes or tubing, areas of loose bark, crevices in stones) or ones they excavate from decaying wood or the pith of plants. Perhaps best known of these are the LEAFCUTTER BEES (Megachile spp.),1 a large group of bees represented by some 140 North American species. Many have developed specialized associations with specific plants, usually in either the pea or aster families; a European species, M. rotundata (ALFALFA LEAFCUTTER BEE) is widely used in the pollination of alfalfa grown for seed. Leafcutter bees and other bees in the family Megachilidae (mason bees, carder bees) carry pollen on the underside of the abdomen.
Once a suitable cavity has been located or constructed, the mother bee will then cut a series of leaf fragments that are used to construct a nest cell. It is then provisioned with enough pollen and nectar to support a single larva, then capped with a few more circular leaf fragments. The process is then repeated, and a series of cells may be produced within a cavity. The larvae consume the food and rapidly develop but then remain in a dormant condition, usually surviving through winter as full-grown larvae and then pupating the following spring. Leafcutter bees produce one generation per year.
Another species-rich group of cavity nesting bees are MASON BEES (Osmia spp.),1 with 150 North American species, most in the western regions. Most mason bees have some sort of metallic coloration (green, blue, purple) and lack bands or other conspicuous markings. Nest cells they produce are usually separated with plugs of mud, although some species use chewed plant matter in nest construction. One species, the BLUE ORCHARD MASON BEE (O. lignaria), is commercially distributed and can be useful for helping to pollinate early flowering plants, such as orchard crops.
Hoplitis1 species are also sometimes known as mason bees, and these may resemble Osmia, although most (but not all) lack metallic coloration and are often black. They may also use similar nest sites but divide cells with a wider variety of materials, including soil and tiny pebbles, chewed wood, and leaves. Almost all Hoplitis spp. occur in western North America.
The SMALL CARPENTER BEES (Ceratina spp.)2 are pith-nesting bees, creating tunnels in the pith of plants exposed by breakage or pruning cuts. Rose, caneberries, butterfly bush, sumac, and other pithy plants are commonly used for establishing nest sites. A series of nest cells are created, separated by chewed pith. After nests are completed the female typically remains at the nest entrance and dies there, further sealing the entrance. The bees mature in later summer but do not emerge until the following year.
Most small carpenter bees are about ⅓ inch long and shiny black, blue, or green. They may superficially resemble several other small bees, particularly some of the sweat bees; however, they can be distinguished by a cylindrical abdomen that terminates in a tiny point.
A wide variety of cavities are used by the CARDER BEES (Anthidium spp.),1 which can nest in soil, among rocks, or in plant stems. Plant hairs are used for lining nests by these bees, and they are thus often found near hairy leaved plants such as mullein (Verbascum) and lamb’s-ear (Stachys). Most native species occur in the southwest, but a European species, A. manicatum (WOOL CARDER BEE), is spreading widely through the continent. Males of the wool carder bee will aggressively defend territory, and they can kill other bees by puncturing them with spines they have on the underside of the abdomen.
1 Hymenoptera: Megachilidae
2 Hymenoptera: Apidae (Xylocopinae)
B. Leafcutter bee with pollen carried on underside of abdomen. DAVID SHETLAR
C. Leafcutter bee removing cut leaf fragment. DAVID SHETLAR
D. Leafcutter bee pollinating sweet pea. WHITNEY CRANSHAW
E. Blue orchard mason bee, Osmia lignaria. SCOTT BAUER, USDA AGRICULTURAL RESEARCH SERVICE
F. Mason bee nesting in drilled wood block. WHITNEY CRANSHAW
G. Small carpenter bee. TOM MURRAY
H. Small carpenter bees reared within raspberry cane. BOB HAMMON, COLORADO STATE UNIVERSITY
I. Wool carder bee at flower. WHITNEY CRANSHAW
J. Wool carder bee male. JIM KALISCH, UNIVERSITY OF NEBRASKA
The great majority of solitary bees nest in soil. Typically a central tunnel will be dug, and along the sides or at the end of the tunnel a series of chambers will be constructed. Each will be provisioned with sufficient pollen and nectar to support one bee, which will complete its development in the chamber.
Characteristics such as soil type, slope, drainage, exposure to sun, and vegetation cover are important in determining the suitability of a specific site for the various ground-nesting bees. Almost all create individual nests, although a few species will sometimes share the main tunnel and nest entrance; however, very favorable sites may support large numbers of bees all nesting in close vicinity.
The cavity-nesting species, like all solitary bees, are not aggressive and will sting only if handled. Furthermore, the sting of almost all solitary bees is much milder than that of the social, colony-producing honey bee and bumble bees.
Several genera (Melissodes, Eucera, Svastra) of ground-nesting bees are known as “long-horned bees” because of the particularly long antennae of the males. They are densely hairy, and larger species have a robust body form that may approach that of a bumble bee. The majority create vertical burrows in flat ground, which they line with a waxlike material. Those that nest in cut banks make a horizontal burrow. Aster family plants, particularly sunflowers, are most commonly used, and these bees carry the pollen in pollen baskets.
DIGGER BEES (Anthophora spp., Habropoda spp.)1 are also quite hairy bees, with most species found in western states. They nest in flat or gently sloping areas of soil. Most prefer lighter soils (loam, sandy loam) and they sometimes will nest in sandboxes and sandy play areas. Anthophora females have very hairy hind legs and often have bands on the abdomen. Habropoda are usually gray, but heavy-bodied in a manner resembling bumble bees, and some similarly will buzz pollinate flowers they visit.
The SQUASH BEES (Peponapis spp.)1 are specialists of cucurbit flowers. Males spend the night in flowers, and most flower visits occur in early morning, shortly after blooms open. They will typically nest in areas where there is patchy vegetation, sometimes in the very near vicinity of the cucurbit plants they visit.
PLASTERER BEES (Colletes spp.)2 are moderate-sized bees (⅓–½ inch), hairy-bodied with bands of hairs on the abdomen. They line their soil burrows with a cellophane-like material they secrete from special glands, and the young are provisioned with a largely liquid mass, in contrast to the semisolid pollen/nectar mixtures provided by most other solitary bees.
B. A Melissoides species of longhorned bee. JIM KALISCH, UNIVERSITY OF NEBRASKA
C. A Svastra species of longhorned bee. JIM KALISCH, UNIVERSITY OF NEBRASKA
D. An Anthophora species of digger bee. KEN GRAY COLLECTION, OREGON STATE UNIVERSITY
E. Squash bees in squash blossom. WHITNEY CRANSHAW
F. A plasterer bee at nest entrance. DAVID SHETLAR
MINING BEES (Andrena spp.)3 comprise one of the largest single groups of solitary bees that occur in North America, with more than 400 species. They are small to moderate in size (⅓–⅔ inch), typically dark colored (black, blue, green), with bands on the abdomen. The hind legs of females are very hairy and used to collect pollen, including the upper segments. Mining bees will usually be seen nesting in sandier soils, often under the cover of a plant.
Andrenid bee leaving nest. WHITNEY CRANSHAW
The “SWEAT BEES” (Halictidae) are also a species-rich bee family, with more than 500 North American species. Some are very brightly colored metallic green, notably those in the genera Agapostemon and Augochlorella, but most have more muted coloration, such as gray-and-white banding.
Sweat bee pupae exposed from soil cells. DAVID SHETLAR
Sweat bees visit a wide variety of crops, particularly those with relatively small flowers. Pollen is carried on the hind legs. Almost all are ground-nesting species. One group important in the pollination of plants in parts of the western U.S. are the ALKALI BEES (Nomia spp.),4 and these prefer saline soils for nesting. One species, N. melanderi, is actively promoted by many alfalfa seed growers as a particularly effective pollinator of the crop, and growers will sometimes create sites that are suitable for nesting.
The name “sweat bee” refers to the habit of some, specifically in the genera Lasioglossum and Halictus, to be attracted to human sweat. This habit sometimes results in stings when they are swatted, but the sting is very mild. Most sweat bees, including the bright, metallically colored GREEN SWEAT BEES (Agapostemon spp.),4 are actually not attracted to sweat.
Halictus sweat bee at nest entrance. DAVID SHETLAR
1 Hymenoptera: Apidae (Apinae)
2 Hymenoptera: Colletidae
3 Hymenoptera: Andrenidae
4 Hymenoptera: Halictidae
A. An andrenid bee. SUSAN ELLIS, BUGWOOD.ORG
B. Andrenid bee at nest entrance. DAVID SHETLAR
C. An Agapostemon species of sweat bee. WHITNEY CRANSHAW
D. Sweat bee. JIM KALISCH, UNIVERSITY OF NEBRASKA
E. A Lasioglossum species of sweat bee. DAVID SHETLAR
