Coleoptera is an order of insects commonly called beetles. The word 'coleoptera' is from the Greek , koleos, meaning 'sheath'; and , pteron, meaning 'wing', thus 'sheathed wing'. The reason for the name is that most beetles have two pairs of wings, the front pair, the 'elytra', being hardened and thickened into a sheath-like, or shell-like, protection for the rear pair, and for the rear part of the beetle's body. The superficial consistency of most beetles' morphology, in particular their possession of elytra, has long suggested that the Coleoptera are monophyletic, but there is growing evidence that this is unjustified, there being arguments for example, in favour of allocating the current suborder Adephaga their own order, or very likely even more than one. The order Coleoptera includes more species than any other order, constituting almost 25% of all known life-forms.
Contributions by John-Nash, Jhml, and Stan Shebs.