See subgroups of the order Coleoptera. Their front pair of wings are hardened into wing-cases, elytra , distinguishing them from most other insects.
However, the number of beetle species is challenged by the number of species in dipterans flies and hymenopterans wasps. Found in almost every habitat except the sea and the polar regions , they interact with their ecosystems in several ways: beetles often feed on plants and fungi , break down animal and plant debris, and eat other invertebrates.
Some species are serious agricultural pests, such as the Colorado potato beetle , while others such as Coccinellidae ladybirds or ladybugs eat aphids , scale insects , thrips , and other plant-sucking insects that damage crops. Some others also have unusual characteristics, such as fireflies , which use a light-emitting organ for mating and communication purposes.
Beetles typically have a particularly hard exoskeleton including the elytra , though some such as the rove beetles have very short elytra while blister beetles have softer elytra. The general anatomy of a beetle is quite uniform and typical of insects, although there are several examples of novelty, such as adaptations in water beetles which trap air bubbles under the elytra for use while diving.
Beetles are holometabolans , which means that they undergo complete metamorphosis , with a series of conspicuous and relatively abrupt changes in body structure between hatching and becoming adult after a relatively immobile pupal stage.
