Odonata
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Odonata is the order that includes dragonflies and damselflies. The order is extremely old, with fossilized remains of specimens dating back 300 million years. Both adults and nymphs in the order are predaceous, feeding on mosquitoes, midges, and other pests. They have long legs which are especially evolved to hold insects captured mid air. Individuals of the order odonata have four wings which can move independently, allowing them to fly both forwards and backwards. They have sharp biting mouthparts to cut up insect prey. Individuals will try to bite humans when handled, but only very large specimens will be able to inflict pain. They do not sting.
Identification
Adults are generally large insects, 2.5 to 9 cm (1-3.5 in.) in length and are often brightly colored. The wings are long, membranous, and veined. The compound eyes are large, often taking up much of the head. The antennae are short and bristle-like. The prothorax is small, the thorax mostly composed of the second two segments. The tarsi have three segments. Male copulatory organs are found on the ventral side of the 2nd abdominal segment. Cerci are present and have 1 segment. In males, they are modified into claspers for mating. The mouth parts are for chewing.
Life Cycle
Dragonflies undergo simple metamorphosis, although the naiaid and adult do not resemble each other. Naiaids are aquatic and carnivorous, feeding on other insects, tadpoles, and even small fish. They capture their prey with modified labium, which are generally folded under the head. When in use, the labium are thrown out quickly to catch the prey in claw-like structures at its apex. This modified structure can reach up to a 1/3 of the naiaid's body length. When the naiaid is done growing, it crawls out of the water, splits the skin along the midline of the thorax, and the adult climbs out. Mating occurs during flight, with the male holding the female's head or prothorax with his claspers, both male and female flying in tandem. The male curls the tip of his abdomen to deposit a sperm packet into a chamber below his second abdominal segment. The female picks up the packet using the tip of her abdomen. Eggs are laid on vegetation near the pond or stream, or on the water's surface.
Habitat
Nymphs are aquatic, and are generally found in freshwater ponds and streams. Adults are usually found in the vicinity of nymph habitats. However, they are very strong fliers and can range over several miles.
Taxonomy
Number of species
There are 5000 species found worldwide, 450 of which are found in North America.
Suborders
There are two suborders in this order, principally separated by wing venation. Other defining characteristics include wing shape, position of wings at rest, and appendages on the abdomen.
Bibliography
Borrer, DJ and RE White. A Field Guide to Insects: America north of Mexico. Houghton Mifflin Company: Boston, 1970. ISBN 0-395-91170-2
Milne, L and M Milne. National Audubon Society Field Guide to North American Insects & Spiders. Alfred A. Knopf, Inc.: 1995. ISBN 0-394-50763-0
Integrated Taxonomic Information System. Accessed June 6 2008.