Dragonfly nymphs hunt ponds before they take wing
Odonata unites dragonflies, damselflies, and odd Epiophlebia damsel-dragonflies as aerial and aquatic predators. Every species has water-dwelling nymphs called naiads, and both stages eat other animals—almost always insects. Odonatology is their science; Odonatoptera names a wider fossil clan.
Johan Christian Fabricius named the order in 1793 from the Greek for tooth, possibly because the mouthparts called maxillae carry obvious teeth. True dragonflies are usually stocky, with big eyes that meet and wings held open at rest; damselflies are slimmer, with separated eyes and wings folded along the body. Adults perch readily but seldom walk. Because dragonfly can mean the whole order, enthusiasts say anisopteran for the narrow group, and warriorfly has been floated as an alternative.
Sizes vary enormously. The Central American damselfly Megaloprepus coerulatus spans 19.1 cm, the helicopter damselfly Mecistogaster linearis stretches 135 mm, and the east Asian Nannophya pygmaea measures only 15 mm. Their Paleozoic relative Meganeuropsis permiana, a griffenfly rather than a true odonate, spanned 71 cm, the largest insect ever. The wider lineage dates to the Late Carboniferous, among the earliest winged insects, with fossils going back 319 million years.
Each of the four wings has its own directly attached muscles, so amplitude, angle, camber and twist can be adjusted independently. A weighted, often colourful cell near each wingtip, the pterostigma, damps the flutter that would otherwise make gliding impossible at speed. Nymphs are stockier, wingless and longer-antennaed, and seize prey with a hinged lower lip called the labial mask. Damselfly nymphs breathe through gills on the tail end, while dragonfly nymphs pump water through the rectum. Larvae will tackle small fish, tadpoles and even adult newts.
Mating is unusual too. Males move sperm from a genital opening near the tail to a secondary organ further forward, then clasp the female by the thorax or head while she curls round into the wheel position. Dragonflies often pair in flight for seconds to a couple of minutes; perched damselflies may take five to ten, and some males scoop out a rival's sperm first.
Source: Odonata
