Harvard University's Caribbean Insects: Thysanura
 

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Coleoptera

The beetles comprise the Order Coleoptera, the most species rich order of insects, with more than 350,000 species described. Beetles account for 40% of insect species – and roughly a quarter of all living species! They are common throughout the world, and show a remarkable variety of shapes, sizes (<1 to 75 mm), and colors.

The name Coleoptera, or "sheath wings," describes one of the main distinguishing features of beetles. While many other winged insects have two pairs of wings, in beetles the front pair of wings is modified into elytra – thickened, hard or leathery coverings that fold back over the hind (flying) wings and protect them at rest. The elytra meet in a straight line down the middle of the back. Thus the beetles have a distinct head and pronotum (covering of the front dorsal portion of the thorax), with elytra arising from the middle of the thorax and often extending back over most or all of the abdomen.
Another feature shared by all beetles is chewing mouthparts, with mandibles (jaws) that are well developed for crushing seeds or chewing leaves or wood. However, just as beetles come in all shapes and sizes, they also have a wide range of foods. While many species are phytophagous (plant-eating), others are predators, scavengers, or coprophages (dung feeders, especially of the family Scarabaeidae).

Habitats range accordingly, from leaf litter and subterranean tunnels to aquatic habitats to trees and shrubs (either on the surface or under the bark).

The beetles undergo complete metamorphosis: from an egg hatches the wingless larval form, which grows larger through a series of molts, then becomes a pupa and finally a winged adult. Most species have one generation per year.

Different families of beetle can often be distinguished by general body form, but more specific identifying characteristics include the shape and length of the antennae, the shape and number of segments in the tarsal portion of the leg, the structure of the head, and the size, shape, and patterning of the elytra.

Common families include the Curculionidae (weevils or snout beetles), Staphylinidae (rove beetles), Carabidae (ground beetles), Cerambycidae (long-horned beetles), and Chrysomelidae (leaf beetles).

 

Please browse and download our Field Guides to insect families and see our Caribbean Taxonomic Literature lists for available PDFs.

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