Insects

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See Insects in Wikipedia, the free encyclopedia.

According to Edward O. Wilson, insects are the "little things that run the world."

Insects are arthropods in the subphylum Hexapoda. Characteristics unique to insects are compound eyes, usually ocelli (light-gathering organs separate from eyes), ectognathous (exposed) mouthparts, well developed maxillary and labial palps, six or more segments per legs, cerci (jointed terminal appendages), tracheal gas exchange, pleural spiracles on the thorax and abdomen, and in many cases, wings.

There are anywhere from 3-30 million insect species, which occupy virtually every possible ecological niche, including detritovores, carnivores, herbivores, pollinators, parasites, seed dispersers. The only habitat not colonized extensively by insects is the open ocean. Currently, there is only one genus of 40 species of waterstrider-like bugs known to live on the surface of the open ocean, Halobates.

Insects are valued as biological control agents and pollinators and for food, silk production, and sheer aesthetics. On the other hand, they are harmful agricultural pests and vectors of disease, such as malaria, sleeping sickness, river blindness, and yellow fever.

There are twenty orders of insects: Archaeognatha (bristletails and rockhoppers), Thysanura (silverfish), Ephemeroptera (mayflies), Odonata (dragonflies and damselflies), Dermaptera (earwigs), Orthoptera (grasshoppers, locusts, katydids, crickets), Phasmatodea (walking sticks), Mantodea (mantids), Blattodea (cockroaches), Isoptera (termites), Thysanoptera (thrips), Phthiraptera (chewing and sucking lice), Hemiptera (true bugs, leaf hoppers, cicadas, plant hoppers, treehoppers, aphids, scales, and mealybugs), Neuroptera (lacewings and ant lions), Coleoptera (beetles), Diptera (flies), Siphonaptera (fleas), Trichoptera (caddisflies), Lepidoptera (butterflies and moths), and Hymenoptera (ants, bees, and wasps).

Eusocial insect orders are Isoptera, Coleoptera, and Hymenoptera (incidentally, eusociality in non-insects has only evolved twice, in fairy shrimp and naked mole rats).