Odonates are among the most ancient of flying insects, their ancestors appearing during the Carboniferous period, 280-350 million years ago. There are two suborders – the Anisoptera (dragonflies) and Zygoptera (damselflies). When at rest, adult dragonflies hold their wings horizontally while damselflies hold them vertically. Larvae (nymphs) of all species are aquatic. All larvae attain a relatively large size and all are predaceous; they are often top predators in freshwater invertebrate communities. Life cycles are relatively long, generally one year in damselflies and one to four years in dragonflies. Odonates usually overwinter as eggs or as nymphs. Adults are relatively long-lived – several weeks to several months. There are about 415 species known from North America, of which 158 have been recorded from Maine (113 dragonfly species and 45 damselfly species).
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