What do the "elytra" protect in beetles?

Beetles are a group of insects that form the order "Coleoptera". The "Coleoptera", with about 400,000 species, is the largest of all orders, constituting almost 40% of described insects and 25% of all known animal life-forms. New species are discovered frequently.

The name of the taxonomic order, "Coleoptera", comes from the Greek "koleopteros" given to the group by Aristotle for their elytra, hardened shield-like forewings from "koleos" for sheath, and "pteron" for wing.

An elytron is a modified, hardened forewing of certain insect orders, notably beetles ("Coleoptera") and a few of the true bugs ("Hemiptera").

In most true bugs, the forewings are instead called hemelytra as only the basal half is thickened while the apex is membranous. An elytron is sometimes also referred to as a shard. In zoology a shard is a tough scale or covering, such as the elytron of a beetle.

The elytra primarily serve as protective wing-cases for the hindwings underneath, which are used for flying. To fly, a beetle typically opens the elytra and then extends the hindwings, flying while still holding the elytra open, though some beetles in the families "Scarabaeidae" and "Buprestidae" can fly with the elytra closed

In some groups, the elytra are fused together, rendering the insect flightless. Some of the ground beetles (family "Carabidae") are a good example of this.