Figure 2.

Palaeozoic and extant insects. (a) Selected developmental stages of Palaeozoic Mischoptera (Megasecoptera) species, from left to right, young nymph with articulated wings arched backwards (wing venation is still absent), older nymph with larger wings already showing wing venation, mature nymph or subadult with straighter wings and adult, with the wings practically perpendicular to the body axis. (b) Two Carboniferous roachoid nymphs, one in dorsal (left) and the other in ventral position, showing long wing pads. (c) Wing development in Palaeozoic and extant Ephemeroptera. Note the articulated and detached winglets in Palaeozoic mayflies and the winglets attached to the body in extant species. From [14].