Insect morphology least three different positions: prognathous, opisthognathous, and hypognathous. In species with prognathous articulation, the head is positioned vertically aligned with the body, such as species of Formicidae; while in a hypognathous type, the head is aligned horizontally adjacent to the body. An opisthognathous head is positioned diagonally, such as species of Blattodea and some Coleoptera. The mouthparts vary greatly between insects of different orders, but the two main functional groups are mandibulate and haustellate. Haustellate mouthparts are used for sucking liquids and can be further classified by the presence of stylets, which include piercing-sucking, sponging, and siphoning. The stylets are
Insect wing was originally proposed in the 19th century. Recent literature has pointed to several ancestral structures as being important to the origin of insect wings. Among these include: gills, respiratory appendages of legs, and lateral (paranotal) and posterolateral projections of the thorax to name a few. According to more current literature, gill-like structures and the paranotal lobe still appear to be among the most important ancestral structures to insect wing origins. Today, there are three main theories on the origins of insect flight. These theories are referred to as the paranotal lobe theory, the gill theory and the dual theory of