Insecta

Invertebrate class that consists of the insects. Insects are by far the largest class of animals: there are over a million species of insect known today and entomologists are continually discovering more.

Insects are divided into 29 orders in two subclasses, Apterygota (wingless forms) and Pterygota (winged forms). In the Apterygota, which include the bristle tails (Thysanura) and springtails (Collembola), there is no, or only very slight, metamorphosis. The Pterygota can be divided into Exopterygota and Endopterygota.

In the Exopterygota the wings develop outside the body and there is but a slight metamorphosis without a pupal stage. The main orders of this division are: Orthoptera (grasshoppers, locusts), Phasmida (stick and leaf insects), Grylloblattodea (rock crawlers), Dictyoptera (cockroaches and mantids), Dermaptera (earwigs), Plecoptera (stone-flies), Isoptera (termites), Anoplura (biting lice), Ephemeroptera (mayflies), Odonata (dragonflies), Thysanoptera (thrips), and Hemiptera (true bugs).

In the Endopterygota the wings develop inside the body and the metamorphosis to adult form is elaborate, involving a pupal stage. The main orders of this division are: Neuroptera (lacewings), Mecoptera (scorpion flies), Trichoptera (caddis flies), Lepidoptera (butterflies and moths), Coleoptera (beetles), Siphonaptera (fleas), Diptera (true flies), and Hymenoptera (ants, bees, wasps, ichneumon flies).

Classification Insecta is in the phylum Arthropoda.