The largest order by number of species is Coleoptera. One in five living animal species is a beetle.
Coleoptera usually have two pairs of wings. The front pair of wings, called elytra, are thick and form a hard shell over the abdomen of the most beetles. Elytra meet in a straight line down the middle of the back. Some have short elytra and may be confused with earwigs but the caudal appendages on beetles are segmented rather a single piece like in earwigs. The hind wings are membranous and are folded under the front wings when at rest. Mouthparts are formed for chewing in adult beetles and immatures but some are modified considerable for piercing or pollen feeding. Weevils may have a snout which can be long and slender giving them the appearance of a sucking mouth but mandibles are at the end.
Immatures can have six legs or be legless almost maggot-like, and generally are called grubs. They come in many sizes and shapes and include the wireworms, white grubs and many others. Some are more worm-like. They generally short antennae, and a distant head capsule. Prolegs are never present but there may be extensions or hooks on the end of the abdomen.
Coleoptera is the largest order of insects, including about 1/4 of all known insects with about 280,000 different species in the world. Food habits are varied. Some feed on living plants; some are predaceous; some are scavengers; and others bore in wood. This order includes some of the best known and most important of our insect enemies. Most of the members are terrestrial, but some are aquatic. Perhaps the most famous members of this group are lady beetles, June beetles and the cotton boll weevil.
Beetles go through complete metamorphosis. They are microscopic to over 2 inches long.
See Coleoptera for individual listings.