Butterflies, along with moths, are easily differentiated from all other insects. They belong to the order Lepidoptera, a name composed of two Greek words, lepis meaning “scale” and ptera meaning “wing,” combined to mean “scale-winged,” which aptly describes their most obvious feature. The wings, as well as the body, are almost always entirely covered with scales. Scales on the wings are usually flat, but the scales covering the body are often long and silky, appearing almost hairlike.
In most respects butterflies and moths are quite similar, but four characteristics usually separate them. In almost all species of butterflies, the antennae end in a club or swelling at the tip, while the antennae of moths are slender or feathery but rarely clubbed. Also, butterflies generally fly during the day, while moths fly primarily at night. However, there are numerous exceptions to the generality concerning moths, since many fly about during the day. Another defining characteristic is that butterflies usually rest with their wings closed and held vertically over the back. Exceptions to this occur during periods of basking when the wings of most species may be spread flat, and the Skippers frequently rest with their wings half spread. Conversely, most moths rest with their wings outstretched and held flat against the surface on which they are resting or drawn back tightly along the sides of the body. Last, and as a general rule, butterflies more often form an unprotected chrysalis in the open, while moths form a tough, silken cocoon in which to pupate.
LIFE CYCLE
In their life cycle, butterflies go through four distinct stages, together known as a complete metamorphosis. These stages of growth are the embryo stage (egg or ovum), the wormlike growing stage (caterpillar or larva), the mummylike transition stage (chrysalis or pupa), and the winged reproductive stage (adult or imago).
Adult females usually lay eggs on or near the food plant that will sustain the caterpillars or larvae upon hatching. The eggs are almost always left unattended and will usually hatch in a few days. In some species eggs are left to overwinter, and in some rare cases they will not hatch for two years or more.
Eggs are very soft when first laid and are usually attached firmly to the food source with a sticky, gluelike substance. Slowly, the egg takes on its particular form and color as the shell dries and hardens. Shape is usually characteristic for the species, and under magnification each egg reveals its own beautiful markings and coloring. It may be round, domed, flattened, elongated, or shaped like a minute barrel, urn, pincushion, spindle, or sea urchin. The egg surface may be pearly smooth or elaborately sculptured with raised or sunken ribbing, horizontal furrows, pits, grooves, knots, spikes, or other ornamentations. Eggs of the Cabbage White (Pieris rapae) are fat yellow cones with intricate lengthwise striations. The Pipevine Swallowtail (Battus philenor) lays large, reddish-brown, almost perfectly spherical eggs, while eggs of the Guava Skipper (Phocides polybius lilea) resemble beautifully ribbed and flattened turbans. Eggs of the Blue Metalmark (Lasaia sula) resemble two pies, one stacked on top of the other.
JANAIS PATCH (Chlosyne janais)
Females of each species instinctively choose the exact food plant on which to deposit their eggs, using an intricate detection system that involves sight, feel, taste, and smell. Many butterflies lay their eggs singly, but others attach several in a single layer or in clusters of up to five hundred, usually to the underside of a leaf. Depending on the species, a female may lay between one hundred and two thousand eggs during her lifetime.
Immediately upon hatching, the young caterpillar usually eats all or a portion of the eggshell as its first meal, thus gaining vital nutrients that have been passed on from the mother. With many species the eating of the shell is extremely important, for the young larvae will not survive if they do not do so. The caterpillar then begins feeding on the leaf or flower it is on. In this nutritive stage of the larva’s life, its entire purpose is to eat—and eat it does. As it grows, it ravenously consumes food at an astonishing rate. By the time the larva has finally become satiated, it may have increased its weight by as much as one thousand times.
Some caterpillars, such as those of the Clouded Sulphur (Colias philodice), are cannibalistic in the sense that they consume eggs or already-formed chrysalides along with foliage if they happen to be attached where the caterpillar is feeding. Caterpillars of another butterfly, the Harvester (Feniseca tarquinius), eat only woolly aphids (family Eriosomatidae) for its food.
EGGS OF THE PIPEVINE SWALLOWTAIL (Battus philenor)
EGGS OF THE GUAVA SKIPPER (Phocides polybius lilea) RESEMBLE TURBANS.
The skin, or exoskeleton, of a caterpillar is incapable of stretching, so to grow any larger, a caterpillar must shed the old, too-tight skin for a new one. Through a complicated process, the skin splits down the back, and the larva emerges with a totally new skin. At first the new skin is much too large, but as the caterpillar continues to eat, this skin eventually becomes stuffed to bursting. Again the splitting process is repeated, and the larva emerges with yet another loose skin to be filled up. This changing of skins is called molting. After each molt the old skin may be abandoned but is more commonly eaten by the caterpillar.
A caterpillar will go through this process several times, the number of molts varying with the species. Most Blues and Hairstreaks (family Lycaenidae) molt only four times, while many of the Metalmarks (family Riodinidae) change skins from four to nine times. The period of a caterpillar’s life between each molt is called a stage or an instar, and the new skin of each instar is often colored and patterned differently from the previous one.
EGGS OF JANAIS PATCH (Chlosyne janais). SOME BUTTERFLIES MAY LAY HUNDREDS OF EGGS IN ONE CLUSTER ON THE UNDERSIDES OF FOLIAGE.
At the end of the last instar, the insect is ready to begin the last phase of its caterpillar life and seeks the most protected place possible. Caterpillars of many butterflies will choose a stem or branch, securely attaching themselves with strands or small pads of silk. Others pupate in silk-lined leaf-nests made from their respective food plants or in ground debris at the base of the food plant. During this transformational phase, sometimes requiring several hours, the caterpillar slowly undergoes a complete change inside the skin and eventually sheds the skin to emerge in a totally different shape—as the chrysalis or pupa. In this form it will remain, mostly immobile and helpless, for several days, months, or in a few instances, years. During this period of its life, the butterfly is vulnerable and open to attack by all sorts of enemies, such as ants, parasitic wasps, birds, lizards, and environmental factors. It is only natural, then, for the caterpillar to seek a protected place when the time comes to pupate.
When the appropriate, species-specific time is completed, yet another change takes place within the pupal case. The cells have multiplied, changed, and rearranged into the various parts of the soon-to-be adult butterfly. The chrysalis changes color; its outer skin becomes almost transparent, and the wing colors of the butterfly become visible inside. After finally splitting the pupal shell and freeing its head, the butterfly uses its legs and contortions of the body to free itself. While it remains motionless, fluids are slowly pumped into the veins of the crumpled wings until completely expanded and dried into their beautiful colorings and patterns.
VARIEGATED FRITILLARY (Euptoieta claudia)
THE BODY
The body of a butterfly is separated into three main divisions: the head, thorax, and abdomen. The head bears the principal sense organs, one of the most obvious being the pair of antennae projecting from the top of the head. Each antenna is composed of short joints or segments, with segments near the tip being larger and causing the antennae to appear knobbed or clubbed. The antennae are quite movable and are used for balancing, touching, hearing, and tasting. Also, most of the main detection sites of smell are situated in the tips. Not having long-distance vision, the butterfly depends more on this sense of smell for detecting odors in search of food. At the base of each antenna is a most essential organ used for orientation, especially while flying.
ZEBRA LONGWING (Heliconius charithonius vazquezae)
Enormous, almost hemispherical compound eyes are just below the antennae. They are among the most complex and intricately designed mechanisms used by animals for seeing. The shape, structure, and position of the butterfly’s eyes enable it to see in all directions except directly beneath its body. The eyes are called compound because they are actually made up of thousands of honeycomb-like facets—between two thousand and twenty thousand facets, depending on the species. Instead of seeing a single light image or object, the butterfly sees a separate image with each tiny facet, making thousands of images. These images are then integrated by its brain into a mosaic picture.
Its eyes are well suited for detecting any type of nearby movement, including butterflies of the opposite sex as well as numerous predators. The eyes are fixed and cannot move, rendering the insect unable to keep objects approaching it in focus. Instead, as the butterfly nears an object (or the object nears it), images move toward the inner part of each eye, with the visual angle decreasing. The spectral or color range visible to the butterfly extends from ultraviolet through yellow-orange and red, fully covering the visual spectrum of humans as well as that of other insects. This mechanism gives the butterfly the broadest spectrum of color vision known to exist in the animal kingdom.
The ability to recognize more colors gives the butterfly many advantages in communication, feeding, protection, and perpetuation of young. Besides the colors visible to us, a butterfly’s wing may reflect a little or a lot of the ultraviolet spectrum to another butterfly. This ultraviolet coloring plays an important role in courtship and mating. Also, since vegetation generally absorbs ultraviolet light, reflection from flowers and foliage serves to maximize color contrast, thus aiding the female butterfly in plant identification for egg deposition.
Also on the head, situated below and extending upward to the side of the eyes, are two soft, furry or scaly palpi. The palpi are sensitive receptors that test the suitability of the food source and protect the mouth and proboscis. The proboscis is divided into two grooved parts or half tubes that are separated when the butterfly first emerges from the pupal shell. The butterfly must spend several minutes twisting and turning the parts to fasten them together securely by the interlocking spines along the edges of each half. This structure, which now forms a long, hollow, flexible tube much like a drinking straw, can be rolled up tightly or unrolled at will and is used to suck up liquid food. Some species of butterflies also have thick, tubular organs for tasting near the tip of the proboscis.
Behind the head is the thick, muscular thorax, divided into three segments and bearing six legs and four wings. Each segment of the thorax has two jointed legs, one on each side of the body. In some species of butterflies, such as the Brush-footed (family Nymphalidae), legs on the first segment are undeveloped, held close to the body, and rarely used, causing the butterfly to appear to have only four legs. The last portion of each leg consists of five tiny segments that form the foot with the last segment ending in a pair of claws. These feet possess organs that enable the butterfly to taste its food. Tasting with the feet triggers an automatic, reflex action that causes the proboscis to uncoil when food is found. In some instances, the female uses the clawed segment to scratch the surface of plant leaves and stems, testing the chemical content to determine if it is the proper plant for depositing her eggs.
Lower Surface (Underside, Ventral)
Above the last two pairs of legs on the thorax are the four wings. Each butterfly wing consists of two delicate membranous sheets with an inner framework of hollow, tubelike veins between the layers. This venation helps strengthen the wings and is in a distinct pattern for most families and species, becoming an important tool in identification. The membrane of the wings is usually transparent, but in most butterflies it is completely covered with thousands of tiny, flat or hairlike scales of various shapes and colors. These scales, shingled in overlapping rows, provide insulation from the cold, protection from rain or dew, and help in flying. They are extremely fragile and, if touched, will readily adhere to the fingers, appearing as colored dust.
CLOSE-UP SHOWING COMPOUND EYE, PALP, AND ROLLED PROBOSCIS.
The third portion of the butterfly’s body is the abdomen, which consists of eleven segments, although only seven or eight can readily be seen. The abdomen is very soft and contains the digestive and reproductive organs. At the tip of the abdomen of the male is a pair of grasping organs used to clasp the female during mating. The abdomen of the female is usually much larger than the male’s due to the large mass of unlaid eggs.
COURTSHIP
Butterflies search for a mate primarily by either perching or patrolling, and almost always it is the male who does the courting. In perching behavior, at a specific time of day the male chooses a certain place—such as a rock, a patch of ground, a post, or a particular tree branch—that offers a visual observation point. There he waits until some moving object comes into view. Since his sight is limited to close-up vision, he must inspect everything that comes into his range of sight, be it wasp, bird, dog, cat, squirrel, human, or a butterfly of any species. If the object turns out to be an unacceptable female, the male returns to his perch to wait for the next passerby. If a male encounters another male of the same species, great exhibitions of “fighting” occur, where the two fly in close association, often spiraling upward until almost out of sight, before breaking apart and going their separate ways. The female of each species is instinctively drawn to likely spots that the male of that species ordinarily chooses, so finding a mate is not usually a problem.
The second method used in seeking a mate is patrolling. A patrolling male flies from one end of a selected site to the other almost continuously until a female of the same species flies into the territory. Here again the female is genetically keyed to locate areas typically selected by the male.
Upper Surface (Upperside, Dorsal)
The male butterfly uses a variety of ways to recognize and attract a female of the same species. One way is by color and its placement on the wings. Since butterflies see the colors humans see, as well as a large range within the ultraviolet spectrum, the male butterfly sees the colors of a female butterfly’s wings entirely differently from how humans see them.
Scale coloration is wondrously complicated. Basically, it is of two types, pigmented and structural. Pigmented colors are actual colors, produced by a pigment within the insect itself or derived from the food plant of the caterpillar. The majority of such colors as blacks, grays, tans, browns, brownish-reds, and some yellows are forms of the chemical melanin, the same pigment that produces freckles and suntans in humans. Ivory to dark yellow colors are usually from organic dyes called flavones, which are retained from the larva’s food plant. The yellow coloring of the Sulphurs and Yellows (family Pieridae) is produced by pterines, which are derived from an excretory uric acid. While some white coloring is made from pigment, others are the result of bubbles of air. The scattering of light by transparent particles produces a white effect in the same way that snow appears white. White hair in humans is similarly produced by tiny air bubbles within the strand of hair that replace the natural color rather than by a white coloring substance.
THE WING SCALES OF THE PIPEVINE SWALLOWTAIL (Battus philenor) DISPLAY A STUNNING IRIDESCENCE.
WING SCALES OF THE PALAMEDES SWALLOWTAIL (Papilio palamedes)
WING SCALES OF THE ZEBRA SWALLOWTAIL (Eurytides marcellus)
Some of the most striking and beautiful colors, such as most of the blues, greens, golds, and silvers, are the iridescent colors that are due to structural features of the scales or hairs rather than pigmentation. Each scale may be ridged or grooved with microscopic striations. The colors are the result of light being reflected from these physical features, much in the same manner as light refracting off a film of oil on water, which produces glittering, changing colors. Although each scale is of only one color, as a general rule there is a mixture of pigmented and structurally colored scales on almost every species of butterfly. On some, such as the Sulphurs, iridescence can hardly be noticed, but on the Common Buckeye (Junonia coenia) or Pipevine Swallowtail, the glow and shimmer are spectacular.
Scent or fragrance also plays an important role in the selection and seduction of a mate. Male butterflies possess special scales that act as dispensers for scents called pheromones. Placement of scent scales varies according to species and may be either scattered among the regular wing scales, grouped in patches, arranged along certain veins, or located in folds along the edges of the lower wings. Some of these scents gain the interest of the female, while others calm the female prior to and during the actual mating. Such scent scales are called androconia, from two Greek words (andr and konic) meaning “male-dust.” Some courtships involve the male performing an elaborate and prolonged dance in front of or above the female, bathing her in his perfume until she becomes settled and receptive for the actual mating.
COURTSHIP DISPLAY OF THE COMMON BUCKEYE (Junonia coenia)
Many species of freshly emerged male butterflies have a strong, noticeable fragrance, frequently comparable to that of flowers. The male Monarch (Danaus plexippus) has a rather musky, exotic scent somewhat resembling the fragrance of a wild rose (Rosa spp.). Scents of other butterflies have been likened to violets (Viola spp.), verbenas (Verbena spp.), meadowsweets (Spiraea spp.), heliotropes (Heliotropium spp.), and even chocolate. A female is readily attracted to this flower fragrance in males, since this is a scent that also entices her to nectar.
TEMPERATURE CONTROL
Butterflies are not as cold-blooded as once believed and described. They are able, under many circumstances, to regulate their body temperature by an assortment of behavioral acts. They do, however, require some heat to begin operations. Most species do not begin flying if temperatures are below 40 degrees Fahrenheit and cannot fly well until they bring their body temperatures to between 60 and 108 degrees, with the optimum body temperature between 77 and 110 degrees. In order to raise the temperature of the muscles that control their wings and legs, they must absorb radiation from the sun or their surroundings or produce the heat themselves.
A MALE JULIA’S SKIPPER (Nastra julia) EXTENDS HIS SCENT SCALES, OR “BRUSHES,” AS PART OF THE MATING RITUAL.
MATING OF THE GREAT SOUTHERN WHITE (Ascia monuste)
Butterflies exhibit six basic positions to obtain and regulate this heat: dorsal, lateral, body basking, dorsally closed, conduction, and “shivering.” In early mornings and during cool periods, butterflies can often be seen basking in the sunlight with wings spread wide. This dorsal basking is the most common position used by most species. A butterfly basking with wings outspread in this manner snaps them together quickly if a cloud or other shadow passes over its body. This conserves heat while making the insect less conspicuous.
Lateral basking is used by some butterflies such as the Large Wood-Nymph (Cercyonis pegala), Hackberry Emperor (Asterocampa celtis celtis), Goatweed Leafwing (Anaea andria), and Sulphurs. They keep their wings closed and practically lie down on their sides, exposing the undersurface of the folded wings to the full rays of the sun. This tactic also helps eliminate a shadow, which might be a giveaway to a predator.
Satyrs (family Satyridae), the Falcate Orangetip (Anthocharis midea), and Blues are primarily body baskers, opening their wings only wide enough for their bodies and base of wings (usually black or dark-colored) to receive some of the sun’s rays. A similar method is termed dorsally closed basking and is seen mostly in the Skippers (family Hesperiidae). Here the hindwings are open with the forewings only partially opened, funneling heat to the body.
In conduction basking, the butterfly chooses a rock, large leaf, the ground, or a dark-colored twig near the ground for perching, not only to absorb the heat from the sun but also to take advantage of the heat rising from the object on which it is resting. This method is used by almost all species, with wings held at their usual position.
Some species, especially those that overwinter or emerge early in the season, such as the Mourning Cloak (Nymphalis antiopa), Question Mark (Polygonia interrogationis), Eastern Comma (P. comma), and Red Admiral (Vanessa atalanta rubria), will “shiver” or rapidly vibrate the wings to warm the body before flying.
Butterflies are just as sensitive to excessive heat as they are to cold. On summer days when the temperature becomes very high, they attempt to prevent overheating by closing their wings dorsally over the back. They may also turn the head and abdomen directly toward the sun; this edge effect keeps the sun from striking the larger wing surface and helps keep the insect cooler. If the butterfly is still too hot, it will take cover in a shaded area.
ROOSTING
As late evening approaches and the air begins to turn cooler, butterflies seek a resting place for the night. Apparently, the major environmental factor that initiates roosting behavior is the decreasing radiation from the setting sun; when clouds pass over the sun before an approaching storm even on a hot summer day, butterflies will seek shelter and assume the roosting position.
For many species the selection of a roosting site is preceded by a short period of extremely active and erratic flight. During this period the butterfly spirals several feet above the vegetation, then dips down to a leaf or grass blade, testing it for suitability. It usually samples several sites before finally settling on one, most often choosing a fairly stable site with no other vegetation close by that would knock the insect from its perch if blown about by high winds. Often the perch is the dead and leafless stem of an herb, perhaps chosen because such a site is not ordinarily visited by ants, one of the butterfly’s worst enemies during periods of immobility. Many butterflies will bask in the sun as long as possible and will sometimes use the basking perch as their roosting site for the night. This has been termed “vesper warming,” and the Least Skipper (Ancyloxypha numitor), Eastern Tailed-Blue (Cupido comyntas texana), and Pearl Crescent (Phyciodes tharos) are noted for such behavior.
Other roosting positions are used, each species of butterfly habitually using a certain type. Some butterflies, such as the Black Swallowtail (Papilio polyxenes), will continue to feed late, then roost on westward-facing slopes or the outermost leaves of westward-facing plants in order to benefit from the last rays of the sun. Other butterflies, such as the Gemmed Satyr (Cyllopsis gemma gemma) and some of the Yellows, choose roosting sites that are shaded from the setting sun and will therefore be illuminated by the rising sun; such sites offer earlier warming the following morning and enable the butterfly to begin feeding sooner. However, where the accumulation of dew is great, even butterflies with east-facing roosting sites have a long wait. Until the sun reaches their wings, dispelling the moisture, the insects remain immobile, unable to fly.
Some species of butterflies randomly select sites each night or may use the site of one type for a few nights and then switch to a different type. During cool spring and autumn nights, undersides of large-leaved trees such as oak (Quercus spp.) or hickory (Carya spp.) are favorite sleeping spots for the Pipevine Swallowtail and Spicebush Swallowtail (Pterourus troilus), especially if the tree branches overhang a little-used road. Heat is trapped beneath the trees, with the temperature commonly several degrees higher beneath the branches. This extra heat provides a much warmer bed for the insects. On hot nights during the summer months, though, they seek the cooler outside tips of the upper branches.
OVERWINTERING
Different species of butterflies have evolved their own special devices for surviving the cold of winter. In the Rio Grande Valley and along the coast where it remains relatively warm all winter and flowering plants are present, many resident butterflies do not have a diapause, or “resting period,” and continue to fly and breed throughout the year. Other species that live and breed in a more northerly part of the state where freezing temperatures regularly occur must pass the winter in another life stage, as either egg, larva, pupa, or hibernating adult.
Several of the Hairstreaks overwinter in the egg stage, while most of the Skippers and some of the Blues overwinter in the larval stage. Swallowtails (family Papilionidae), Longwings (family Nymphalidae), Whites (family Pieridae), and Sulphurs spend the winter in the chrysalis or pupal stage, the exception being the species that wander into the state from Mexico or Florida and may breed but are not considered residents. Some butterflies, such as the Mourning Cloak, Hackberry Emperor, Red Admiral, Question Mark, and Painted Lady (Vanessa cardui), pass the winter in a semihibernating state, tucked away behind loose bark, in narrow cracks of buildings, or in hollows of posts or trees. They are able to survive the freezing cold of winter by thickening the blood (haemolymph) with certain natural substances (glycerol, sorbitol, or alcohol) that act in a manner similar to that of antifreeze in a car radiator. During this time of severe cold, a butterfly’s metabolic rate becomes noticeably slowed; instead of continually eating, the insect is sustained mainly from stored body fats. Any period of warmth and sun, however, will see the butterfly out partaking of oozing sap, partially thawed fruit, or any substance containing amino acids.
The Monarch is an exception and cannot endure freezing in any stage of its life cycle. For its survival, it migrates to warmer climates in Mexico, where it lives out the winter resting on certain roosting trees in areas that have been used by migrating butterflies for hundreds of years.
LONG-DISTANCE FLIGHTS
Other species of butterflies travel long distances as well, both northward and southward and at different times of the year. The Painted Lady, Common Buckeye, Cloudless Sulphur (Phoebis sennae), Dainty Sulphur (Nathalis iole), Little Yellow (Pyrisitia lisa lisa), Gulf Fritillary (Agraulis vanillae incarnata), and Great Southern White (Ascia monuste) all move northward each spring, rearing many broods along the way. With the shortening day length of fall, some of the existing population heads back southward, often into areas of nonfreezing temperatures; the majority of the insects do not make a return flight and are killed by advancing freezes. The ones that do return as far as the semitropical climate continue to reproduce with no winter diapause. By spring the population will have again built to such numbers that it must disperse in search of available food plants, so a portion of the population once again heads northward.
A few species of butterflies, such as the Checkered White (Pontia protodice), are notorious for long-range dispersal. Dispersal movements, or emigration, differ from migration in being random and erratic in nature, whereas migration follows a habitual and predictable pattern. Checkered Whites exhibit a prime example of uncertain behavior, for they may be encountered almost anywhere in the United States during one breeding season and then not seen in the same area again for several years. In the southernmost portion of the state the Snout (Libytheana carinenta) may become extraordinarily abundant after drought-breaking rains in the fall and disperse hundreds of miles. Rio Grande Valley residents such as the Julia Longwing (Dryas iulia), Zebra Longwing (Heliconius charithonius vazquezae), Amymone (Mestra amymone), Yellow Angled-Sulphur (Anteos maerula), and Ruddy Daggerwing (Marpesia petreus) are sometimes sighted in the Panhandle during these late summer and early fall months.
DANGERS TO CATERPILLARS AND CHRYSALIDES
Butterflies, as do all other living creatures, have their enemies. In the larval, plant-eating stage, one of the worst and most common pests is the introduced fire ant (Solenopsis invicta). This was not always such a serious danger, but in recent years fire ants have spread to the extent that rare is the yard that does not have its bed or two of them. Often the ants form their mound in an out-of-the-way place, and a lot of damage can be done to eggs, caterpillars, and chrysalides before the ants are finally noticed. Once a caterpillar or chrysalis is found, a group of ants will congregate and entirely consume the “future” butterfly in only a few minutes. It is time well spent to walk about a butterfly garden at least once a week to check for these ferocious beasts. Especially look along branches and leaves of the food plants.
First-brood caterpillars are especially susceptible to various fungi during the early spring months, when there are many cloudy days, an abundance of rain, and sudden drops in temperature. Plentiful stands of the food plant in protected areas will best ensure survival of the larvae during this time.
Spring rains sometimes cause plants to die because of excessive moisture. This loss is a normal occurrence and something the larvae can cope with. Usually, they simply move to nearby areas of plants that survived in drier habitats.
Parasitism of the caterpillar, as well as the eggs and pupae, by various species of tiny flies and wasps is a common hazard. The gardener has little control in this situation. If a plentiful source of the food plant is available, there are usually enough healthy larvae left to continue the breeding cycle. The amount of parasitism varies from brood to brood and season to season, so the population as a whole usually levels out.
The worst predation of butterfly caterpillars is probably by birds and spiders. Caterpillars are the staple food of young birds in the nest and are eaten quite readily by the adult as well. Several species of spiders lurk among plant foliage, taking many caterpillars, especially the smaller, early-stage ones. Caterpillars have evolved various methods of protection from their enemies, such as camouflaged coloration, spines, or distastefulness, but still the loss is staggering.
DANGERS TO ADULTS
Even after butterflies have emerged and are on the wing, their lives are still fraught with many dangers. The first broods to emerge in the spring are susceptible to late freezes and sudden thunderstorms. The insects can sometimes survive by finding a crack beneath tree bark or by snuggling low to the ground among dried grasses to escape freezing temperatures.
They are not so lucky during really windy rainstorms. During turbulent weather, adult butterflies most commonly seek shelter beneath large leaves. If high winds accompany the rain, the leaves are turned over, exposing the butterflies to the driving rain. Also, the wind often loosens the butterfly from its hold on the leaf, forcing it to the ground, where it is either drowned or beaten to death.
Praying mantises (Mantis spp.), various spiders (order Araneae), red wasps (order Hymenoptera), carabid beetles (family Caraidae), ambush bugs (family Phymatidae), assassin bugs (family Reduciidae), robber flies (family Asilidae), dragonflies (order Odonata), anoles and green snakes (order Reptilia), and birds (order Aves) all readily feed on butterflies. Birds frequently catch butterflies on the wing; other predators lie in wait or stalk the nectaring insects. The large webs of the orb-weaving spiders are another great hazard to butterflies on the wing. Nighttime predation by such animals as raccoons (order Carnivora), opossums (order Marsupialia), mice and flying squirrels (order Rodentia) are a major cause of mortality in some species. During this roosting period, the butterflies are quiescent and totally defenseless against any kind of disturbance.
During the summer months the single most common disaster to butterflies is loss of nectar plants. Nectar sources frequently die as a result of drought, mowing, or herbicides. Also, a poorly planned garden that leaves a gap with no plants in flower usually results in either the butterflies dying or having to seek food elsewhere.
Early freezes in the fall take a toll on the adult butterfly population. Some manage to survive the cold by hiding in well-protected spots and will be seen on the wing for several weeks after the first frost or two. With the exception of the species that migrate or hibernate, extremely cold weather eventually kills both the nectar plants and the butterflies. Often larval food plants are killed before the feeding larvae reach a stage in which they can overwinter successfully.
METHODS OF PROTECTION
Eggs, once they are laid, are at the mercy of the weather, parasitic wasps, and predators ranging from fire ants to beetles to birds. The best the mother butterfly can do to protect her future young is to conceal the eggs as well as possible and to choose a well-protected place on or near a healthy food source. Commonly, eggs are of a pale color, either whitish, greenish, or pale yellow, and are generally deposited on the foliage. Eggs deposited at the base of a leaf or along stems often become much darker in color after a day or so, blending more readily with their surroundings and becoming less conspicuous to predaceous eyes. Some butterflies use a strategy of wide dispersal of the eggs as a measure of safety, laying only one egg per plant on widely separated plants. Other species use “overabundance,” laying a hundred or more eggs in one cluster.
The most vulnerable period of a butterfly’s life is during the larval or caterpillar stage, and it is then that greatest mortality occurs. The extent of their built-in defenses against diseases is not known, but their obvious weapons against predator attack are numerous.
As with eggs, concealment is one of the major visual defenses for caterpillars. They are often pale green, as in the case of the Cabbage White and Lyside Sulphur (Kricogonia lyside), and remain immobile and hidden beneath a leaf except when feeding. They may be spotted, blotched, or striped to blend with the stems and branches of their food plants. The lengthwise blackish and reddish-brown striping of the Common Buckeye make it practically indistinguishable from the brownish striations of the branches of agalinis (Agalinis spp.), one of its food sources.
The art of appearing as something else is one of the most fascinating strategies evolved by larvae. First instar caterpillars of some of the Swallowtails along with the Viceroy (Limenitis archippus) and Red-spotted Purple (L. arthemis) appear as nothing more than fresh bird droppings and are overlooked by all but the most observing eye. Last instar larvae of some of the Swallowtails such as the Spicebush, Eastern Tiger Swallowtail (Papilio glaucus), Two-tailed Tiger Swallowtail (P. multicaudata), and Palamedes Swallowtail (P. palamedes), have large, conspicuous eyespots on the humped thorax that give the frightening impression of a snake’s head.
The Red Admiral, Painted Lady, and Variegated Fritillary (Euptoieta claudia) use silk to form a leaf- or flower-nest in which to hide. They eat, rest, and occasionally even form the chrysalis within these shelters. Caterpillars of the Texas Emperor (Asterocampa clyton texana), Theona Checkerspot (Thessalia theona), Janais Patch (Chlosyne janais) and Bordered Patch (C. lacinia adjutrix) are gregarious in the first instars. By remaining clustered together, they are offered some protection by sheer numbers. If disturbed, they initiate a fright aspect by twitching, jerking, or rearing their heads in unison.
AN ASSASSIN BUG (FAMILY REDUVIIDAE) THREATENS A NORTHERN OAK HAIRSTREAK (Satyrium favonius ontario).
Larvae of the Gulf Fritillary, Zebra Long-wing, Mourning Cloak, and Common Buckeye, among others, are covered with branched spines that, although completely harmless, appear fearsome enough to cause would-be predators to have second thoughts. The egg-laying tubes of some parasitic wasps are not long enough to reach the body of the larva because of the spines, so parasitism is not possible. The larvae of the Monarch, Pipe-vine Swallowtail, and Queen (Danaus gilippus thersippus) have long, floppy tentacles that wave about menacingly when they are crawling or feeding. Swallowtail larvae possess a most formidable chemical defense—a scent gun. Molest one of these critters, and a two-pronged apparatus suddenly springs up out of the thorax, releasing a strong, almost overpoweringly obnoxious scent. These fleshy horns, called osmeteria, are usually bright orange or reddish. The predator attacking one of these larvae experiences a double whammy: the shock of a large, bright object suddenly appearing and a totally unexpected spraying with a horrible odor.
OSMETERIA OF THE EASTERN BLACK SWALLOWTAIL (Papilio polyxenes asterius)
And of course, some caterpillars are just plain bad tasting. Having eaten plants that contain poisonous chemicals, the larvae retain the poisons, making themselves unpalatable to predators. Such terrible-tasting caterpillars do not bother to hide. They are usually brightly or strikingly colored and remain in the open, conspicuously and confidently munching away. Birds that feed on a bad-tasting caterpillar usually do not make a second mistake.
Once caterpillars have selected the site for pupation and the change from larvae to pupae has been completed, the pupae are unable to move from the site. Because they are so vulnerable, butterfly pupae have evolved extremely variable shapes and colors that help them hide from their many enemies. Pupae of the Longwings have odd-shaped extensions that break up the overall outline, making them look more like a dead, tattered leaf than a tasty morsel; the chrysalides of the Cloudless Sulphur are either green or brown, perfectly matching the stems and foliage of Partridge-pea (Chamaecrista fasciculata), its food plant. The pale green shell of the Monarch is decorated with a partial band of black and gold with occasional golden flecks, which blends perfectly with its leaf support. Pupae of the Gulf Fritillary and the Question Mark have light-reflecting silver or gold spots or splashes, which help them blend into the sunlight-and-shadow areas of the foliage. The black-speckled yellow chrysalis of the Janais Patch would be most conspicuous if placed against green foliage, but when attached among the pale stalks of its larval food plant, it is much less noticeable to predators. The intricate blackish and brownish mottling of Swallowtail pupae resemble jagged bits of wood or bark, appearing as an extension of a leaf rachis or a broken branch.
CLOUDLESS SULPHUR (Phoebis sennae)
Because adult butterflies are also food for a number of predators, they, too, have evolved many different protective devices to survive. While we view the intricate colors, shapes, and patterns on a butterfly’s wing with awe and wonder, they have been perfected by that particular insect through a long process of natural selection for a protective rather than aesthetic purpose. One of the most dramatic protection methods is cryptic or camouflage coloration and patterning, which allows the butterfly to blend into its surroundings. Frequently, the wings have the shape or pattern of objects such as broken pieces of bark, the mottling of pebbled ground, or the ribbing and coloration of dead leaves. One of the more common butterflies exhibiting this protective resemblance is the Goatweed Leafwing. When not feeding, the Goatweed Leafwing’s usual resting place is on the ground or the trunk of a tree. The tannish or pale brown coloring and venation of the closed wings so resemble a dead leaf or a patch of bare ground that the butterfly seems to disappear the moment it comes to rest.
CLOUDLESS SULPHUR (Phoebis sennae)
LARVAE OF THE PALAMEDES SWALLOWTAIL (Papilio palamedes) ACTUALLY RESEMBLE A SNAKE’S HEAD.
Wing edges of the group of butterflies known as Anglewings (Polygonia spp.) are conspicuously angled, cut, or scalloped. These irregular wing shapes, along with a dull brownish or grayish coloration and contrasting markings, obliterate their outline, helping them escape detection.
A disruptive pattern is commonly used by species such as the Zebra Swallowtail (Eurytides marcellus) and Zebra Longwing. When viewed alone, the sharply and distinctively striped wing pattern is readily visible, but when one of these butterflies comes to rest in dappled shade, it becomes lost among the sunshine and shadows. Large contrasting borders and bands on the Bordered Patch and Red Admiral and the broad yellow bands on the upper surface of the Giant Swallowtail (Papilio cresphontes) break up the overall color and shape. With this type of disruptive coloration, the insect may be seen but is not easily recognized for what it is. Eastern Tiger Swallowtails are dramatically visible when gathered around a mud puddle or nectaring at a clump of roadside flowers, but when they glide among tree branches or shrubbery, the yellow and black striping enables them to disappear in the filtered sunlight.
Butterflies that exhibit dull or cryptic coloration on the undersurface of their wings often have a contrastingly bright upper surface. Some have prominent, eyelike spots to frighten prospective predators. Such coloring is used by the Common Buckeye, whose prominent eyespots are concealed by the brownish, camouflaging pattern of the undersides. When disturbed, the Common Buckeye suddenly opens its wings and takes off in nervous, erratic flight, startling the would-be predator with brilliant colors and large “eyes” suddenly flashed in its face.
THE LARVA OF THE GIANT SWALLOWTAIL (Papilio cresphontes) APPEARS TO BE BIRD DROPPINGS.
LONGITUDINAL STRIPING HELPS THIS COMMON BUCKEYE (Junonia coenia) CATERPILLAR BLEND IN WITH BRANCHES.
FIERCE, BRANCHING SPINES OF JULIA LONGWING (Dryas iulia) DETER MANY PREDATORS.
THE VIVID GREEN COLORING OF THIS CLOUDLESS SULPHUR (Phoebis sennae) LARVA ENABLES IT TO BLEND INTO THE SURROUNDING FOLIAGE.
BRANCHLIKE PUPA OF THE GIANT SWALLOWTAIL (Papilio cresphontes)
Some butterflies have brightly colored spots or body parts that draw the attention of predators away from the vital sections of the body. The red spots on the lower wings of most of the Swallowtails and orange-tipped upper wings of the Arizona Sister (Adelpha eulalia) and Falcate Orangetip serve this purpose. The constantly moving “tails” and bright eyespots of the Hairstreaks make it most difficult for predators to distinguish head from tail. Close inspection often reveals portions of the wings missing near these false “parts,” as if a bird or other predator had aimed for what it took to be a head and was left with a mouthful of wing instead.
Such butterflies as the Monarch, Queen, Gulf Fritillary, Pipevine Swallowtail, and Polydamas Swallowtail (Battus polydamas) rely on their showy appearances to attract the attention of predators by “thumbing their noses.” This warning, or aposematic, coloration is found in butterflies genuinely dangerous or unpalatable to would-be predators. These insects retain poisonous alkaloids or toxins from the larval food plants on through the pupal stage and are quite indigestible. The toxins usually cause a bird or lizard to vomit, become disoriented, and otherwise feel quite ill. Usually one taste is enough. Monarchs and Queens, for instance, feed on members of the Milkweed Family (Asclepiadaceae), which contain cardiac glycosides, or heart poisons. Milkweed plants produce these chemicals as protection against herbivores, but larvae of the Monarch and Queen have developed the ability to tolerate and store these poisonous chemicals, making both the larvae and the adults poisonous to predators.
Some quite harmless and palatable butterfly species have evolved colors and patterns that mimic the unpalatable ones, thereby deriving protection because would-be predators mistake them for the bad guys and leave them alone. For instance, the “edible” Viceroy has developed coloration and wing venation much like that of the Monarch and is rarely molested. The Viceroy feeds primarily on willow (Salix spp.) and cottonwood (Populus spp.) and retains only small amounts of poisonous properties from its larval food plants. Mimics of the noxious Pipevine Swallowtail are many, including other Swallowtails such as the Black and Spicebush. In the eastern half of the state there are occasional black female forms of the usually yellow Eastern Tiger Swallowtail that look quite similar to the poisonous Pipevine. Even though the Red-spotted Purple has no tails and is not even a close relative, its general color is such that it can easily be mistaken for the noxious Pipevine, giving the insect an edge in its struggle for survival.
HOME GARDENERS HAVE MANY OPPORTUNITIES TO PROVIDE PLANTS FOR BUTTERFLIES.