The Evolutionary Pathway to Insect Flight - a Tentative Reconstruction

Abstract

Abstract Studies on non-pterygotan Ectognatha revealed that the construction of the winged Pterygota is based on lepismatid organization and that the first steps of mastering the air were attained already in the common ancestor of Ectognatha by adaptations in the context of jumping which is still retained in Machilidae (Archaeognatha). In these, the terminalfilum and the ectognathan 3-segmented antenna permit attitude control of the body. The acquisition of the mandibular dicondyly led to climbing on vascular plants and exploitation of plant tips as food since the late Silurian. The problems of beginning sustained flight with flapping wings are discussed. A scenario with intermediate gliding and one without gliding are presented. The corresponding parts of the sclerites and muscles of the three subcoxal leg segments found in lepismatids are still recognizable in the pterygotan pterothorax. The wings are composed of the paranota and part of the most basal subcoxal leg segment. It is concluded that wing elongation was impossible without flexing the wings on the back already during early evolution and that the inability to flex the wings is secondary. Wing flexing nearly ab initio was possible by a mechanical switch between the states of flight and non-flight. This led to the neopterous construction of the wing base.