Glossary - Bedfordshire Odonata

Glossary of terms used in Odonata references

Dragonflies and damselflies are complex organisms, and many of the terms used to describe their biology, life cycle, and behaviour can be unfamiliar or highly specialised.

This glossary explains the specialised terminology commonly used in reference materials on dragonflies and damselflies (order Odonata). Many terms have synonyms or alternative scientific names; where relevant, these are cross‑referenced for clarity.

The posterior section of the odonate body, consisting of ten externally visible segments (S1-S10). It houses the digestive tract, reproductive organs, and spiracles. In males, S2-S3 bear the secondary genitalia, while S10 supports the anal appendages. Highly flexible, enabling manoeuvrability during flight, mating, and oviposition. See also: Posterior, Caudal, Tergite, Sternite.

Anal Appendages (Cerci)

Paired structures at the distal end of the abdomen. In males, the superior and inferior appendages form a species-specific clasping mechanism used during tandem and copulation. Morphology is often diagnostic. Female cerci are typically reduced. See also: Apex, Distal, Tandem.

A distinctive arrangement of hindwing cells in many Anisoptera (especially Libellulidae). Its shape (e.g., 'boot-shaped') is a key family-level diagnostic feature. See also: Venation, Triangle, Subtriangle.

Andromorph / Homeomorph

A female colour morph resembling the male in pattern and coloration. May reduce male harassment or aid thermoregulation. Opposite: Heteromorph. See also: Dimorphic, Polymorphic.

Pertaining to the suborder Anisoptera (dragonflies), characterised by robust bodies, wings held horizontally at rest, and hindwings broader at the base. Opposite: Zygopteran.

Antehumeral Stripes

Longitudinal pale stripes on the dorsal thorax, often used in identification. See also: Humeral Stripes, Thorax.

Directional term meaning toward the head or leading edge of a structure. Opposite: Posterior. See also: Cranial, Dorsal, Ventral.

Referring to the distal tip of a structure, such as the wing apex. Opposite: Base / Basal. See also: Distal, Apex, Pterostigma.

A key crossvein near the wing base, important in venation analysis. See also: Venation, Triangle, Node.

Referring to the base of a structure, such as basal wing cells near the thorax. Opposite: Apex / Apical. See also: Proximal, Costa.

Producing two generations per year. See also: Univoltine, Semivoltine, Multivoltine.

A raised ridge or keel on the body, common in larval morphology. See also: Sclerite, Spine.

Relating to the posterior end of the body. Opposite: Cranial. See also: Posterior, Abdomen.

Caudal Lamellae

Three leaf-like appendages at the end of the abdomen in damselfly larvae. Function as external gills and stabilisers during swimming. See also: Larva, Setation.

A facial sclerite between the frons and labrum. Useful in identification. See also: Frons, Labrum, Sclerite.

Belonging to the same species.

The leading edge vein of the wing, providing rigidity and aerodynamic stability. See also: Anterior, Venation, Node.

The proximal leg segment articulating with the thorax. See also: Trochanter, Femur, Proximal.

Toward the head. Opposite: Caudal. See also: Anterior, Posterior.

Active at twilight.

The chitinous exoskeleton providing support and protection. Hardens through sclerotization after emergence. See also: Sclerite, Exuvia.

A trait that reliably distinguishes one species from another.

A hormonally regulated developmental arrest triggered by environmental cues.

Exhibiting two distinct forms within a species. See also: Polymorphic, Andromorph, Heteromorph.

Farther from the body or point of attachment. Opposite: Proximal. See also: Apex, Apical.

The upper surface of the body. Opposite: Ventral.

Shedding of the exoskeleton during larval growth. See also: Instar, Stadium.

Transition from aquatic larva to aerial adult. See also: Teneral, Exuvia.

Eggs inserted into plant tissue. See also: Epiphytic, Exophytic.

Eggs laid on the surface of plant material. See also: Endophytic.

Summer dormancy.

Eggs released freely into water or onto its surface. See also:

The shed larval exoskeleton after emergence.

The thick, muscular leg segment used in prey capture. See also: Tibia, Tarsus, Coxa.

A distinct morphological or colour variant.

The upper facial sclerite between the eyes. See also: Clypeus, Occiput, Vertex.

The 'cheek' region of the head capsule. See also: Frons, Occiput.

Aerial foraging behaviour involving interception of flying prey.

Having incomplete metamorphosis; lacking a pupal stage.

The typical female colour form. Opposite: Andromorph.

Winter dormancy.

Humeral Stripes

Dark stripes along the humeral suture of the thorax. See also: Antehumeral Stripes.

Transparent or glass-like, usually describing wings.

The sexually mature adult stage.

A developmental stage between moults. See also: Stadium, Ecdysis.

The overall impression or 'feel of a species in the field, based on general appearance and behaviour.

Paired structures on the larval labium used in prey capture. See also: Labium, Larva.

The prehensile larval mouthpart used to capture prey. See also: Labial Palps, Larva.

The anterior 'upper lip' covering the mandibles.

The aquatic immature stage. See also: Naiad, Nymph, Prolarva.

Toward the side of the body. Opposite: Medial.

A jaw-like mouthpart used for biting and chewing. See also: Labrum, Labium.

Along the midline. Opposite: Lateral.

Showing no variation in form. Opposite: Dimorphic, Polymorphic.

Producing more than two generations per year.

Aquatic juvenile stage of hemimetabolous insects. See also: Larva, Nymph.

A structural notch on the costa influencing wing flexibility. See also: Costa, Subnode.

Common term for the larval stage. See also: Naiad, Larva.

Occipital Triangle

A triangular region on the dorsal head between the eyes.

The posterior part of the head capsule. See also: Frons, Gena.

Ocellus (Ocelli)

Simple photoreceptive organs aiding flight stability.

Any member of the order Odonata.

A single optical unit of the compound eye.

The act of laying eggs.

A sclerotised structure used to insert eggs into substrates.

A lateral sclerite of an abdominal segment. See also: Tergite, Sternite.

Exhibiting multiple forms. Opposite: Monomorphic.

Toward the rear of the body. Opposite: Anterior.

The first post-hatching stage.

A dorsal plate on the prothorax.

The anterior thoracic segment bearing the forelegs.

Closer to the body or point of attachment. Opposite: Distal.

A waxy bloom on the cuticle of some adults.

Pseudopterostigma

A coloured wing patch in female demoiselles.

A thickened, pigmented cell near the wing apex.

See Venation.

A hardened plate of the exoskeleton. See also: Sclerotization, Cuticle.

The chemical hardening of the cuticle forming sclerites.

Completing a generation every two years.

Sensory hairs detecting mechanical or chemical stimuli. See also: Setation.

The pattern or arrangement of setae.

A rigid, pointed projection of the cuticle. See also: Seta, Carina.

Openings for gas exchange.

Site of Special Scientific Interest. A UK conservation designation for areas of high ecological or geological value.

The period between moults. See also: Instar.

The ventral sclerite of an abdominal segment. See also: Tergite, Pleurite.

A vein branching from the node.

A flexible junction between sclerites.

The fused meso- and metathorax supporting wings and legs.

A conspicuous patch of colour near the end of the abdomen, especially in damselflies.

A mating posture where the male clasps the female with his anal appendages. See also: Wheel Position.

The distal leg segment composed of tarsomeres.

The scientific system of classifying organisms.

A small lobe covering the wing base. See also: Costa, Arculus.

A newly emerged adult with soft cuticle.

The dorsal sclerite of an abdominal segment. See also: Sternite, Pleurite.

The central body region containing flight musculature.

The long leg segment between femur and tarsus.

Triangle / Subtriangle

Wing venation landmarks important in Anisoptera identification.

A small leg segment between coxa and femur.

Producing one generation per year.

The pattern of veins in the wings.

The underside of the body. Opposite: Dorsal.

The top of the head between the eyes. See also: Frons, Occiput.

A ventral flap on segment 8 in females lacking an ovipositor.

A spine on the underside of segment 8 in some damselflies.

The copulatory posture in which the male transfers sperm to the female. See also: Tandem, Secondary Genitalia.

Pertaining to damselflies (suborder Zygoptera). Opposite: Anisopteran.

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