Definitions refer to usage in this book.
Terms included within a definition and that occur elsewhere in the glossary are italicised where to do so may assist comprehension.
accompanying behaviour A foraging strategy of adult dragonflies that entails accompanying large, slowly moving objects over grassland.
acute zone Area in compound eye having interommatidial angles less then 0.2 degrees; also termed a fovea.
aedeagus Tip of penis.
aestivation Summer diapause.
alpha male Territorial male who is dominant at the time of day when most receptive females arrive at the rendezvous.
anal pyramid The sharp, triangular projection at the posterior tip of the abdomen of anisopteran larvae made up of the epiproct and two paraprocts.
andromorph Colour form of female resembling the male
anterior pole The end of the egg that contains the micropyles (through which sperm enter), through which the prolarva issues and which faces the outside of the substrate enclosing eggs laid endophytically.
apolysis Separation of the new from the old cuticle before ecdysis; after apolysis but before ecdysis the developmental stage is termed pharate.
arthropod A jointed-limbed animal that possesses a hard exoskeleton.
assimilation efficiency (AE) Measure expressed (as a percentage) as 1 – (dry weight of faeces produced)/(dry weight of food consumed).
autotomy Voluntary severance by an animal of part of its own body.
bank lurker A non-territorial male who intercepts females as they fly near the water.
batch Pertaining to eggs. See clutch.
biochemical oxygen demand Measure of the deoxygenating ability of a sample of water.
biological control (biocontrol) Suppression of a pest organism or the reduction of the damage it causes (to a level considered acceptable to humans) by manipulating the pest’s predators, parasites, parasitoids or pathogens.
biological productivity Total mass of organic material manufactured by organism or ecosystem during a specified time.
biomass Weight of living material, usually expressed as dry weight, carbon, nitrogen or calorific content, in all or part of an organism, population or community.
biota A characteristic association of animals and plants.
biotope Local area containing a biota.
blastokinesis Revolution of the embryo within the egg during embryogenesis; equivalent to katatrepsis.
BOD Biochemical oxygen demand.
bout Applied to oviposition, a spell of uninterrupted egg laying during an episode that may include several bouts, each separated by perching.
branchial basket Complex of gills lining the inner wall of the rectum of Anisoptera.
burrower Dragonfly larva that normally rests with all or almost all of the body hidden within sediment.
bursa copulatrix Part of the female genitalia that receives and stores sperm after insemination.
carrying capacity Maximum number of organisms (of a given species) that a habitat can sustain.
caudal appendages Epiproct and paraprocts arising from abdominal segment 11 or its vestiges.
caudal lamellae Flattened, leaf-like caudal appendages of Zygoptera that are used for respiration and swimming.
chitin The tough, horny, nitrogenous polysaccharide that makes up the bulk of the insect cuticle.
circadian rhythm Periodically repeated fluctuation (with a period close to 24 hours) maintained by an innate time-measuring sense; sometimes termed the ‘biological clock’.
clasper Dragonfly larva that at rest uses the legs to hold the body tightly against a support, usually a stem or a branch.
clutch Complement of oocytes that mature together to produce a batch of eggs which are typically laid during an episode.
cohort Members of a generation that share a time (usually a year) of hatching or emergence.
commensal An organism that benefits from its association with its host but does not impose a cost on it.
compound eye The typical eye of insects (very well developed in dragonflies) comprising many, separate, hexagonal units (facets), each with its own lens and efferent nerve, which together contribute to a composite image.
congeneric Belonging to the same genus.
conspecific Belonging to the same species.
courtship Behavioural interaction between a male and a female that facilitates copulation; refers especially to displays by males.
crepuscular Active during twilight.
crypsis Aspect of the appearance (usually coloration, pattern or posture) of an organism that renders it inconspicuous.
cuticle Non-cellular outer layer of the body wall of an insect covering the epidermis.
damselfly Dragonfly of the suborder Zygoptera.
definitive host Pertaining to a parasite, the host in which reproduction takes place.
diapause State of suspended or retarded development that may supervene at some stage or stages in the life cycle and that typically constitutes an anticipatory response to conditions unfavourable for uninterrupted development. See dormancy.
diel Pertaining to the 24-hour period; the 24-hour period.
dispersal Spatial displacement by individuals (usually adults) that, being centrifugal, causes them to become farther apart. See migration.
diurnal Pertaining to the light period during the diel.
divided emergence Separation of a diel emergence cohort into two instalments by the advent of low temperature during stage 1 of emergence.
dormancy Reduction in activity or metabolism in direct response to conditions unfavourable for uninterrupted development.
dorsal Pertaining to the back or upperside of an animal.
dragonfly Member of the order Odonata.
ecdysis (plural ecdyses) Moulting; the shedding of the outer skin.
eclosion Moulting or issuing from the egg.
ecological energetics The study of the energy transformations that occur within ecosystems.
ecosystem Natural unit consisting of living and nonliving parts that interact to form a stable system.
ectotherm Animal that regulates its body temperature by gaining (or losing) heat from its environment.
embryogenesis The development of the embryo.
emergence Ecdysis from larva to adult; the final moult.
emergence curve Curve describing the seasonal pattern of emergence, usually on a cumulative basis. The notation EM50 denotes the time at which 50 per cent of the annual population has emerged.
endemic Restricted to a particular geographic region.
endocuticle Thick, colourless, elastic, innermost layer of cuticle. See epi- and exocuticle.
endophytic Pertaining to oviposition into a substrate, usually plant tissue. See epiphytic and exophytic.
endotherm Animal that regulates its body temperature by generating heat within the body by its own activity.
energy budget An inventory for an individual or population showing the balance between energy acquisition and expenditure.
epibiont Organism attached to the outside of the body of a carrier organism.
epicuticle Very thin, refractile membrane, at most a few micrometres thick, forming the outer layer of the cuticle. See endo- and exocuticle.
epiphytic Pertaining to oviposition when eggs are placed on, and usually adhere to, the surface of a substrate, typically a plant. See endophytic and exophytic.
epiproct Middle, dorsal, backwardly pointing, appendage thought to be a vestige of the 11th abdominal segment; it is sharp and robust in anisopteran larvae.
episode Applied to oviposition, a single visit to the oviposition site during which egg laying may occur in several bouts, each separated by perching.
eurytopic Able to tolerate a wide range of environmental conditions.
eutrophic Possessing abundant, sometimes excessive, nutrients; usually applied to aquatic habitats. See mesotrophic and oligotrophic.
evolution Cumulative, heritable change in the organisms in a population.
exocuticle Rigid layer, usually amber-coloured, between the endocuticle and epicuticle.
exophytic Pertaining to oviposition when eggs are dropped, or washed, from the abdomen without being placed into or directly onto a substrate. See endophytic and epiphytic.
Exopterygota Insects (including dragonflies) in which the wings develop externally during the later larval stadia and which lack a pupal stage.
exploitation competition Competition between coexisting individuals (of the same or different species) that entails use of the same resource.
exuvia (plural exuviae) Outer skin(s) shed at the end of each stadium.
F-o Last larval stadium. Compare F-1, F-2 etc., denoting the penultimate and antepenultimate larval stadia.
facet See ommatidium.
facultative Optional; contingent on external stimuli. See obligate.
fecundity Number of fertilised eggs laid by a female during her lifetime.
feeding Behaviour that follows prey capture; handling and ingestion (the predatory sequence). See foraging.
fitness The relative ability of an organism to transmit its genes to the next generation.
flier Dragonfly that, when active at the rendezvous, typically remains on the wing except for brief interludes of perching. See percher.
flying season Period of the year during which reproductively mature adults are active.
foraging Behaviour that increases the likelihood of prey capture. See feeding.
frons Anterior-facing plate on the upper surface of the head between the compound eyes.
gamont Immature sexual form of gregarine Protozoa.
genitalia External reproductive organs.
gonad Organ in which gametes are produced; a testis or ovary.
growing-degree day Day when the ambient temperature has exceeded the lower threshold permitting growth.
growth ratio Proportionate change in size of a specified part of the body between one stadium and the next.
guarding Behaviour of male adult when escorting a female, usually his recent copulation partner, and usually while she is ovipositing. He may be attached to her (in contact guarding) or unattached, flying close to her (in non-contact guarding).
habitat Place where a given species or community lives.
habitat selection The process by which an organism exercises a preference for one type of habitat.
haemolymph Internal circulatory fluid conveying nutrients and hormones around the body.
handling time Interval, beginning with prey pursuit, during which a predator is sufficiently preoccupied with its current prey that it cannot resume searching.
hanging type A type of emergence in which, during the resting stage, the angle between the anterior part of the body and the horizontal is 90-180°.
head-arrester system Fields of hair-like structures on the back of the head and on the neck which help to stabilise the dragonfly in flight.
heterothermy A type of thermoregulation that combines methods used by an ectotherm and an endotherm.
hibernation Suspension of development during winter.
hider Dragonfly larva that rests beneath a thin layer of detritus or leaf litter.
highest steady density (HSD) Equilibrium number of sexually active males in a given area of the rendezvous resulting from intramale interaction.
host An organism attacked by a parasite, parasitoid or pathogen.
hyperparasite Parasite that parasitises another parasite.
hyperparasitoid Parasitoid that lives at the expense of another parasitoid.
imago (plural imagines) The adult stage of an insect.
in copula In the wheel, or mating, position.
inclusive fitness The extent to which (all factors considered) an animal contributes genetical material to its descendants.
insect An arthropod in which the body is typically divided into three regions: head, thorax and abdomen.
insolation Exposure to the sun’s rays.
instar Interval between two apolyses. See stadium.
interference competition Competition between coexisting individuals (of the same or different species) that entails direct interaction, including predation.
interspecific Between species.
intramale sperm translocation (IST) Transfer by a male of sperm from his primary gonopore to his secondary genitalia.
intra-odonate predation Predation by one species of dragonfly on the same or another species of dragonfly; when the predation is intraspecific it is termed ‘cannibalism’.
intraspecific Within a species.
invertebrate Animal lacking a vertebral column; a non-chordate metazoan.
Joule Unit of work performed or energy consumed.
K strategist Organism that produces few offspring and contributes to a population that stays close to the species’ carrying capacity.
katatrepsis Revolution of the embryo during embryogenesis.
labial suture Hinged joint of the larval labium situated between the pre- and postmentum.
labium Fused second maxillae, specialised in the dragonfly larva to form a prehensile organ that can be extended during prey capture.
larva Developmental stage between egg and adult. The term ‘nymph’ has sometimes been used instead of larva. It is ambiguous, having been used at different times to denote (1) the larva of an exopterygote insect; (2) the last larval stadium of such an insect when the wing sheaths are prominent; and (3) the pupa of an endopterygote insect. The term ‘nymph’ is not needed in reference to the Odonata.
latency habitat For a metapopulation of a given species, the suboptimal habitat type serving as a habitat reserve where mainly larvae, rarely F-o exuviae, and almost no adults are found, and where a population cannot normally survive for more than one generation without immigration. See secondary habitat and stem habitat.
lentic Pertaining to standing water.
lifetime reproductive success (LRS) The survival of progeny of an individual.
littoral Pertaining to the marginal strip of relatively shallow water in which rooted macrophytes can grow.
localisation Behavioural sequence of the adult by which site attachment develops.
lotic Pertaining to flowing water.
macrophyte Macroscopic, multicellular, water plant at least part of which is submerged.
maiden flight Flight or succession of flights that take a teneral adult from the emergence site to the place of first protracted rest or the place from which flight is no longer oriented away from the emergence site.
mating success Number of copulations achieved by an individual during a lifetime.
mating system General behavioural strategy employed when obtaining mates.
maturation period See prereproductive period.
melanic Darkened by black cuticular pigments.
mesotrophic Pertaining to an aquatic habitat having an intermediate nutrient content. See eutrophic and oligotrophic.
metamorphosis Irreversible changes in morphology, physiology and behaviour that take place during the transition from the F-o stadium to the adult.
metapopulation Population of a species that has components coexisting in, and exchanging individuals among, habitat types offering different opportunities for reproduction and larval survival. See latency habitat, secondary habitat and stem habitat.
microhabitat Particular part of a habitat in which an individual is normally found during a specified stage of its life cycle or when performing a specified activity.
micropyle Conical or nipple-like projection at the anterior pole of the egg through which sperm travels when entering the egg.
microtrichia Minute hair-like setae on an external body surface, e.g. the wing.
migration Spatial displacement that entails part or all of a population leaving the habitat where emergence took place and moving to a different habitat where reproduction ensues; migration may be obligate or facultative, and migrating adults may or may not travel in aggregations. See dispersal.
moult Process of shedding the cuticle; ecdysis.
natural selection Elimination of an inferior genetic trait from a population through differential survival and reproduction of individuals bearing that trait. Widely regarded as the main mechanism giving rise to evolution. See sexual selection.
niche Functional role and position of an organism in an ecosystem.
non-trivial flight Type of spatial displacement which, in contrast to trivial flight, is characterised by relatively protracted, long-range, persistent, non-appetitive movement (e.g. migration).
nymphochrysalis An aquatic developmental stage of a hydracarine mite immediately after it has dropped off the dragonfly host.
obelisk posture Position adopted by a percher, usually when the sun is at the zenith, such that the abdomen points towards the sun and the body’s shadow is minimised.
obligate Invariable. See facultative.
oligotrophic Pertaining to a body of extremely clear water having a low nutrient content and low productivity. See eutrophic and mesotrophic.
ommatidium (plural ommatidia) A single optical unit of the compound eye; each ommatidium is a cone-shaped structure comprising a lens, a crystalline cone and light-sensitive retinulae; also called a facet.
ontogeny Development of the individual from the fertilised egg to adulthood.
operational sex ratio The proportion of males and females active at the rendezvous.
optimal foraging theory Proposition that fitness is likely to be enhanced by foraging strategies that increase the net rate of energy or nutrient intake.
oviposition Act of laying eggs.
ovipositor The egg-laying apparatus of the female.
paraprocts Three robust, backwardly directed appendages, on larva and adult, arising from abdominal segment 10.
parasitism Interaction between members of two species in which one (typically small) species, the parasite, lives in or on the other species, the host, from which it obtains benefit (e.g. food or shelter) at the host’s expense; the host is not necessarily killed by the interaction. See parasitoid.
parasitoid Parasite that invariably kills its host and so in this respect resembles a predator.
parthenogenesis Development of an egg without fertilisation.
partivoltine Completing a generation in more than two years.
percher Dragonfly that, when active at the rendezvous, typically remains on a perch from which it makes brief flights.
pharate Condition in which, before ecdysis, the outer and inner layers of the cuticle have become separated. See apolysis.
phenology The study of life cycles and seasonal distribution.
philopatry Tendency of an adult, after maturation, to return to the water body whence it emerged.
phoresy (is) Interaction during which one species is carried on the outside of the body of another species without being parasitic on it.
postmentum Unpaired part of the larval labium proximal to the labial suture.
prementum Unpaired part of the larval labium distal to the labial suture; it bears the paired palpal setae.
prereproductive period Phase of adult life, including the teneral stage, that precedes the attainment of reproductive maturity and therefore the flying season.
prolarva First, often very abbreviated, larval stadium.
prothorax The most anterior thoracic segment; the one lacking wings.
proximate cues Attributes of their external environment to which individuals respond positively when behaving in a specific way.
pruinescence Bloom on body surface of adults, more often males, caused by supracuticular pigment that typically strongly reflects ultraviolet light.
pseudopterostigma Counterpart of pterostigma, though less robust or well defined, as found in Calopterygidae.
pterostigma Pigmented ‘cell’ near the distal end of the leading edge of the fore and hind wings of almost all species.
pursuer A non-territorial male who pursues females for up to 50 metres.
reflex immobilisation Antipredation behaviour, of larva or adult, characterised by persistent immobility; also termed ‘death feigning’ or ‘thanatosis’.
rendezvous Venue where males and females meet as a direct prelude to copulation; if there are several such venues, typically one – the primary rendezvous – is sought preferentially by the most competitive males.
resting stage The phase during stage 2 of emergence when the head, thorax and legs are out of the exuvia and attached to it by the posterior part of the abdomen, which remains inside.
roosting site attacker A non-territorial male who grasps females at the roosting site.
satellite Male who stations himself near a dominant male in a dominant-subordinate relationship and tries to intercept approaching females or steal copulations when the dominant male is preoccupied.
secondary habitat For a metapopulation of a given species, suboptimal habitat type serving as a population reserve with a near-normal population structure but in which the small population cannot normally survive for more than one generation without immigration. See latency habitat and stem habitat.
semivoltine Completing a generation in two years.
sentinel position Upright position of a male when in tandem during guarded oviposition.
seta (plural setae) Hollow, hair-like structure which is an extension of the cuticle.
sexual selection Selection by one sex for specific traits in adults of the opposite sex, often exercised through courtship behaviour. See natural selection.
siccatation Suspension of development during the hot, dry season.
sink population Typical occupant of a latency or secondary habitat.
site attachment Association over time between an individual adult and a particular site.
site fidelity Duration of site attachment.
sneaker A non-territorial male who patrols along the edge of an occupied territory trying to intercept females.
speciation Evolution of a new species.
sperm competition Competition between the sperm of two or more males, within a single female, for fertilisation of her eggs.
sperm displacement The process by which the male repositions the sperm of previous rivals during copulation.
sperm precedence Measure of proportion of eggs laid that are fertilised by sperm received during the most recent insemination.
spermatheca Small, sac-like branch of the female reproductive tract (of insects and other arthropods) in which sperm may be stored.
spermatodesm Specialised spermatophore from which sperm are not released promptly after insemination.
spermatophore Packet of sperm transferred to the female during copulation.
sprawler Larva that uses the long, laterally extended legs to support the body on or within a matrix, usually of detritus or macrophytes.
spring species Species that spends the last winter before emergence as a stadium F-o larva and consequentially typically emerges synchronously and early. Also called a Type 1 species. See summer species.
stadium Stage of morphological development between two successive moults; not, strictly speaking, equivalent to an instar. In almost every case when the word ‘instar’ has been used, ‘stadium’ correctly conveys the intended meaning.
stealer A non-territorial male who attacks and splits tandem pairs.
stem habitat For a metapopulation of a given species, optimal habitat type that persistently produces large populations, emigrants from which supply suboptimal latency and secondary habitats.
stenotopic Unable to tolerate a wide range of environmental conditions.
subordinate male Displaced or submissive male in a male-male encounter.
succession Progressive changes in a community of organisms from initial colonisation to the establishment of a stable (climax) state.
summer species Species that spends that last winter before emergence in a stadium before F-0 and consequently typically emerges later and with less synchronisation than spring species. Also called a Type 2 species.
tandem linkage Physical connection, as a prerequisite for copulation, formed by the male grasping the female’s head or prothorax with his anal appendages.
taxonomy Study of the classification and naming of organisms.
temperature coefficient Rate of increase of an activity or process resulting from an increase in temperature of 10°C; sometimes referred to as the Q10.
teneral Condition of a larva or adult, soon after moulting, when the cuticle is almost colourless and still unhardened.
territory Area occupied by an individual (or occasionally more than one individual of the same species) and defended against intruders.
testis (plural testes) Primary reproductive organ of males, producing spermatozoa.
thanatosis Reflex immobilisation, sometimes termed death feigning.
thermal conformer Individual whose body temperature equates to ambient temperature.
thermoregulation Process by which an individual maintains its body temperature within a particular range and largely independent of ambient temperature.
thorax Body section of an insect between the head and abdomen, comprising three segments, often fused together, and bearing the legs and wings.
tracheae Breathing tubes of insects, opening to spiracles on the outside of the body.
trivial flight Type of spatial displacement which, in contrast to non-trivial flight, is associated with an obvious immediate goal, such as thermoregulation or escape.
ultimate factors Environmental factors that exert selection pressure that maintains a specific trait.
ultraviolet light Wavelengths between 40 and 400 µm of the electromagnetic spectrum.
univoltine Completing a generation in one year.
upright type A type of emergence in which, during the resting stage, the angle between the anterior part of the body and the horizontal is 0-120°.
ventral Pertaining to the underside of an animal.
vitelline membrane Structureless, colourless investment of the yolk within the egg.
voltinism Number of generations completed within a year.
voucher specimen Specimen collected and preserved for future investigatory need.
vulvar scale Small flap, an extension of the ventral surface of abdominal segment 8, used during exophytic oviposition to regulate the flow of eggs.
wanderer A non-localised, non-territorial male who travels through or near many territories when searching for females.
warriorfly Dragonfly of the suborder Anisoptera.
water lurker A non-territorial male who searches oviposition sites and forms tandems with females that are submerging or surfacing and may even pursue them beneath the water.
wheel position Copulatory position in dragonflies.
wing sheaths Transparent cuticular envelopes that contain the developing wings during the last few larval stadia.