Odonata

Lore & Background

The two major groups are distinguished: dragonflies (Anisoptera) are usually bulkier with large compound eyes together and wings spread up or out at rest, while damselflies (Zygoptera) are more slender with eyes apart and wings folded along the body at rest. Adult odonates can land and perch but rarely walk. Odonates have large rounded heads covered mostly by well-developed compound eyes, legs specialized for catching prey in flight, two pairs of long transparent wings that move independently, and elongated abdomens. Flight is direct, with muscles attaching directly to the wings, allowing independent control of each wing. Most families have a pterostigma on the wing's leading edge, which assists in gliding by preventing flutter. Male Odonata have complex genitalia, including grasping cerci and a secondary copulatory organ. Mating involves the male grasping the female by the thorax (Zygoptera) or head (Anisoptera) while the female bends her abdomen to form the 'wheel' position. Males are competitive and may remove rival sperm. Eggs are laid in water or on vegetation, hatching into pronymphs that develop through 9–14 molts into voracious aquatic nymphs, then into flying teneral adults.

Reader's Guide

Odonata are significant as one of the earliest groups of winged insects, with members of their total group (Odonatoptera) appearing in the Late Carboniferous, and crown group Odonata appearing in the Late Triassic. The extinct Meganisoptera, such as Meganeuropsis permiana with a wing span of up to 71 cm, were related but not part of the modern order. Odonata are closely related to mayflies and several extinct orders in the group Palaeoptera. Their phylogenetic relationships continue to be studied, with debates about the classification of suborders such as Anisozygoptera and the use of terms like Epiprocta. The World Odonata List considers Anisoptera, Zygoptera, and Anisozygoptera as well-understood suborders. Odonates are ecologically important as predators throughout their life cycle, controlling insect populations in both aquatic and aerial environments.

Did You Know?

• The smallest living dragonfly is Nannophya pygmaea from east Asia, with a body length of 15 mm.
• Male Odonata can remove rival sperm from a female using cerci at the tip of the abdomen.
• The extinct Meganisoptera included Meganeuropsis permiana, the largest insect of all time, with a wing span of up to 71 cm.

Anatomy of a Master Aerial Hunter

These insects present a strikingly specialized body plan built for life in the air. Their large, rounded heads are dominated by well-developed compound eyes that deliver sharp vision, supplemented by three small ocelli and a pair of short antennae. The mouthparts sit on the underside of the head and, in adults, consist of straightforward chewing mandibles. Two pairs of long, transparent wings extend from the thorax, and the legs are adapted specifically for snatching prey mid-flight. Perhaps the most remarkable feature is the flight mechanism: unlike most other winged insects whose muscles attach to the thorax, odonates use direct flight muscles that connect straight to the wings. This arrangement grants each of the four wings fully independent control over amplitude, frequency, angle of attack, camber, and twist. Along the leading edge near the wingtip, most families carry a pterostigma—a thickened, hemolymph-filled, often colorful patch bounded by veins. This heavier section is not decorative; without it, self-exciting vibrations called flutter would take over above a critical speed and make gliding impossible.

From Aquatic Ambush to Aerial Pursuit

Every odonate begins life as an aquatic larva, known variously as a naiad or nymph, and every stage of its existence is devoted to predation. These are almost entirely insectivorous carnivores, though the larval form will seize and consume anything it can overpower, ranging from small fish and tadpoles all the way up to adult newts. The nymphs themselves look quite different from the adults: they carry stockier, shorter bodies, smaller eyes, longer antennae, and less mobile heads. Their most distinctive feature is the labium, a modified lower lip that extends outward as a prehensile labial mask for grabbing prey. Respiration also differs between the two major groups—damselfly nymphs breathe through external gills attached to the abdomen, while dragonfly nymphs draw air through a specialized organ in the rectum. Once they emerge as adults, odonates become superb aerial hunters. Their legs are finely tuned for intercepting and gripping prey in mid-air. They can land and perch on vegetation, but they rarely, if ever, walk.

A Spectrum of Sizes and Forms

The order Odonata encompasses an astonishing range of body sizes. At the opposite end, the tiny east Asian dragonfly Nannophya pygmaea measures just 15 millimeters in body length, while species of the damselfly genus Agriocnemis are the smallest odonates overall, with wingspans of only 17 to 18 millimeters. Beyond sheer size, the two major suborders differ in build and posture: Anisoptera (true dragonflies) tend to be bulkier with large compound eyes pressed together and wings held spread at rest, whereas Zygoptera (damselflies) are more slender, with eyes set apart and wings folded along the body. A small group of damsel-dragonflies, the Epiophlebia, bridges these two forms. The dedicated scientific study of all this diversity is called odonatology.

Deep Time: 319 Million Years of Flight

The lineage that would become modern dragonflies and damselflies stretches back to the Late Carboniferous, making Odonatoptera one of the earliest groups of winged insects on Earth. The crown group Odonata itself first appears in the fossil record during the Late Triassic. Their Paleozoic relatives were colossal: Meganeuropsis permiana, a Permian giant dragonfly from North America belonging to the extinct order Meganisoptera (the griffenflies), reached a wingspan of up to 71 centimeters and a body length of 43 centimeters, making it the largest insect of all time. Though the griffenflies are close cousins, they are not part of the modern order Odonata in its restricted sense. They share with mayflies a distinctive way of articulating and holding their wings at rest, linking them within the broader Palaeoptera assemblage. The prehistoric family Tarsophlebiidae occupies a position either as a basal lineage of Odonata or as their immediate sister taxon.