dragonflies

Anisoptera is the infraorder of insects called dragonflies. It is below the Order Odonata, which includes both dragonflies and damselflies. It was formerly treated as a suborder. In 2003, Anisoptera was combined with Anisozygoptera into the new suborder Epiprocta, and Anisoptera was demoted to an infraorder. This reordering has not been universally accepted.

There are about 3,016 still surviving (extant) dragonfly species in 348 genera in 11 families worldwide. There are 330 species in 69 genera in 7 families in North America north of Mexico. Odonata Central lists 110 dragonfly species in Minnesota.

Dragonflies occur worldwide on every continent except Antarctica. They have been recorded in every county in Minnesota.

Dragonfly adults are predatory. They feed on a wide variety of flying insects, including mosquitoes, flies, butterflies, moths, and smaller dragonflies. They only eat living insects, and they almost always capture them in flight. Dragonfly young, known as naiads, are aquatic. They feed on any living thing that moves through the water, including aquatic larvae of mosquitoes and flies, other dragonfly naiads, tadpoles, and small fish.

Dragonfly adults do not survive the winter. With most species, the naiads spend northern winters in water under ice in a state of suspended animation called diapause. With some species, the females lay their eggs on a shore, where they are washed into the water in the following spring.

Dragonflies are large flying insects. The flight is agile, strong, and sustained.

The head is bulbous, nearly as long as wide. The back of the head is hollowed out. The compound eyes are extremely large and fill most of the head. They meet at the top of the head in all species except clubtails. There are three small simple eyes (ocelli) in a triangle on top of the head. The antennae are minute. The lower lip (labrum) has a middle lobe and two strongly toothed lateral lobes. This is the feature that gives the infraorder its name. The word Anisoptera is Latin for “toothed ones”.

The abdomen is slender and has ten segments. On the female of most species, there is a subgenital plate on the underside of segment 8, but on some species, there is a needle-like, egg-laying apparatus (ovipositor) there. At the end of segment 10 there are three appendages. On the male, these function as claspers and are used to grab and hold the female during mating.

There are two pairs of transparent, membranous wings with many small veins. They are held flat and away from the body when at rest. The hindwings are larger and have a different shape than the forewings. On the leading edge (costal margin) of each wing, there is a node (nodus) near the middle. The nodus allows the wing to flex downward but not upward during flight. Near the wingtip on the costal margin there is a thick, opaque, blood-filled cell (stigma). The stigma is thought to dampen vibrations when in flight. Unlike most winged insects, dragonfly wings are attached directly to the flight muscles, not to chitinous plates of the exoskeleton.

The legs are spiny. On the front legs of the male, one row of spines is modified into a brush that the male uses to clean its eyes.

Sources

7, 17, 18, 24, 27, 29, 30, 82, 83.

It was on a tree that was in the water (ice).

Fairview Twp., Cass Lake

It was on a tree that was in the water (ice).