The Clavus and Jugum Venation in the Wings of Beetles (Coleoptera) and Its Genesis

摘要

The homology and nomenclature, as well as hypothesized pathways of the historical development of the clavus and jugal lobe of the beetle hind wings are discussed. The reconstructed plan of the clavus venation is largely similar to the venation patterns observed in some representatives of Corydalidae (Megaloptera). Its main apotypic characters are the following: the first anal cell was reduced at the wing base and the second anal or cuneiform cell appeared. This venation pattern is supposed to resultfrom consolidation of the area around the claval furrow base at the earlier stages of the beetle wing evolution. In particular, longitudinal compressing the bases of RA, M, CuP, and 1A resulted in the development of a complex sclerite composed of the distal median plate and the bases of CuP and 1A. After this new reinforced connection between the remigium and the clavus appeared, the proximal parts of CuP and 1A were partly or completely reduced since they were no longer needed to maintain the structural integrity of the beetle wing.