Coleoptera Coleoptera Introduction Beetles. The largest order with over 130 families and 350,000 species worldwide or about one-third of all described animal species. About 25,000 species occur in North America, north of Mexico, but only about 1200 of these are purely aquatic.
Many additional species are semiaquatic.
Adults with chewing mouthparts, fore wings modified into a hard elytra, which covers the hind wings and usually most of the abdomen, antennae with 11 or fewer segments. Pupae are exarate, pads of forewings thickened, antennae with 11 or fewer segments, usually above water. Some adults are short-lived, some larvae take nearly a full year to complete their growth, a few take several years. There are normally 3 to 8 larval instars. The last instar larva usually leaves the water to find a pupation site.