ADEPHAGA Antennae usually thread-like: tarsi 5-jointed; hind wings with an oblongum and one or two cross-veins near middle (fig. 3) : first visible abdominal sternum completely divided by Bind coxal cavaties. Larvae predaceous, campodei f orm (fig. 23) and usually with definite tarsi and paired claws.
The Adephaga consist of a single super family, the Caraboidea, whose characters are as given above. Ten families are in cluded here and the most important are as follows: The Cicindelidae (fig. 4) are, known as tiger beetles and rank among the most vo racious of carnivorous insects. Their slen der legs, acutely toothed mandibles, very prominent eyes and the presence of a jointed hook at the apex of the lacinia of the maxilla, are special distinguishing fea tures. They are often brightly coloured and run and fly with great rapidity in sun shine. The species of Cicindela frequent sandy places, including the sea-shore, where their larvae construct deep burrows and feed upon other insects which they suddenly seize when near these re treats. About i,800 species are known: four species inhabit the British Isles and i 14 species accur in N. America, but the majority frequent hot countries.
The Carabidae (fig. 5) comprise the carnivorous ground beetles of which over 17,00o kinds are known. They are distinguished from the Cicindelidae by the absence of the jointed hook to the lacinia, and by the fact that the clypeus does not extend over the bases of the antennae. They mostly occur in the soil, under stones, in moss, under bark, etc., and are active runners : many species have hind wings reduced or absent, and the elytra soldered together. Since these beetles and their larvae prey upon other in sects, worms, etc., they are dis tinctly useful to man: a few spe cies may attack cereals and straw berries, but this is exceptional.
The Dytiscidae (fig. 6) are a large family of carnivorous water beetles. Their hind legs function as oars, being flattened and pro vided with lcng hairs. In the males of some genera three seg ments of the fore tarsi are ex panded to form sucker pads which enable them to hold the females during pairing. Their larvae prey upon other forms of aquatic life including even tad poles and small fish : their long sickle-like jaws are perforated by a fine canal through which the body-fluids of their victims are imbibed. The family is world-wide and includes about 2,200 species.
Other families include the Gyrinidae or whirligig beetles which swim on the surface of fresh water, and the curious Paussidae which inhabit ants' nests.