Odonata

The Odonata (toothed one)family includes the dragonflies (Anisoptera) and damselflies (Zygoptera). Both are carnivorous.

Dragonflies are generally larger , and rest with the wings held out at the sides, whilst damselflies hold the wings over the body and have slender bodies. Both have 2 sets of narrow transparent wings. The abdomen is normally longer than any wing. They hunt in daylight and are the only animal that can predict where the prey will be (other predators follow the prey) and fly to intercept at a future point. No one knows how they can do this with such a small brain (not surprisingly ,the military are interested in finding out so they can better target missiles) .The kill rate of dragonflies is the highest of any hunter at 80%.

They are colourful and fly by water.

There are about 5000 species, the larvae are nymphs which live in shallow water and eat mosquitoes ,snails and some small fish, they moult about 8-16 times and can be 5cm in length. For the final moult they climb out of the water onto vegetation to emerge as adults. Initially the adults are sexually immature but develop over 2 weeks. Then they congregate at the edge of water to mate. The males establish territories and will fight other males who enter it, sometimes to the death.

They mate in a wheel position (the tip of his abdomen holds her head, and her abdominal tip attaches close to his thorax where his sperm are stored. Sperm competition occurs ,so males protect females until the eggs are laid.

Like butterflies , each species of Odonata have unique secondary sexual appendages - this 'lock and key' means different species can't interbreed

The large compound eyes (which consist of 30000 units ,or ommatidia) of dragonflies meet at the top of the head and can give 360 degree vision. The damselflies have well separated eyes.

Damselflies have 4 terminal abdominal appendages, whilst dragonflies have 3.

Unlike other insects which beat their wings synchronously , Odonata can beat the front and rear pair separately, this allows them a range of acrobatic flight methods including flying backwards , hovering and virtually midair pivots

The larvae of damselflies have 3 flat plates at the rear of the abdomen which act as gills. Dragonflies have gills in the intestinal tract. When startled damselfly larva swim like a fish by moving the gills, while dragonfly larva use jet propulsion through the anus.

The larvae hunt by shooting out their prehensile lower jaw (like Alien!), this is done in under 0.03 seconds by increased haemolymph pressure controlled by abdominal muscles

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