In the Achorutidae the head is forwardly directed, the tergum of the prothorax conspicuous, and the spring small or vestigial.
The prothorax is much narrowed, whereas the other segments (especially the mesothorax) are greatly enlarged; the legs long and slender, the anterior pair often very much longer in the male than in the female; the tarsi fouror five-jointed; but in some genera (e.g.
The Raphidiidae or snake-flies (q.v.) are remarkable for the long, narrow, tapering prothorax which gives the appearance of a constricted neck, while the female has a long ovipositor.
The tergite of the prothorax (pronotum) is prominent in all beetles, reaching back to the bases of the elytra and forming a substantial shield for the front part of the body.
They are relatively shorter and broader insects than the Embiidae with large prothorax and long wings, which have a transverse line of weakness at the base and are usually shed after the nuptial flight.
The prothorax is short and the mesothorax very long, the three pairs of legs closely similar, the wings often highly modified or absent, and the cerci short and unjointed.
The abdomen is oval, sandy-grey in hue and beset with warts and bristles; the prothorax forms a mobile neck for the large square head, which carries a pair of long and powerful toothed mandibles.
Among the longhorn beetles, the prothorax scrapes over a median file on the mid-dorsal aspect of the mesothorax.
The Embiidae are feeble, somewhat soft-skinned insects with the prothorax small and the mesothorax and metathorax elongate.
Paired erectile plates (patagia) are borne on the prothorax in moths, while in moths, sawflies, wasps, bees and other insects there are small plates (tegulae) - see Fig.