46

N. Chari et al.

Fig. 4.5 Wing joints of an insect

Direct Muscles

In all insects, the upward movement of the wings is due to the contraction of indirect

dorsoventral muscles or vertical muscles. As a result of this contraction, the wing

membrane moves up and with the pleural process act as a fulcrum. These muscles

may not be always homologous in different insect groups. Direct Flight Muscles are

found typically in Odonata (Dragonfly) and Blattaria (Cockroach) (Fig. 4.6).

Indirect Muscles

The up and down movements of the wing are produced by indirect muscles due to

changes in the shape of the notum (tergum plate), which is not directly attached to

the wing base. Indirect Flight Muscles are typically found in Diptera (Housefly) and

Hymenoptera (Honey bees). The wing movements, Transverse Sections (TS) and

structure of thorax are shown in Figs. 4.7 and 4.8 in a semi-diagrammatic fashion

modified from various sources.