Dimorphism of the Metasternal Wing in Agabus raffrayi and A. labiatus (Coleoptera: Dytiscidae) Questioned

Previous descriptions of species of the dytiscid genus Agabus Leach that are dimorphic in the shape of the metasternal wing are shown to be erroneous. One of the two specimens described as a form of A. labiatus (Brahm) with broad metasternal wings was identified as A. uliginosus (Linnaeus), and the other specimen was not found. The study of a large material of A. pallidus Omer‐Cooper and A. raffrayi Sharp from Ethiopia suggests that what previously was interpreted as one dimorphic species in fact are two distinct species. These two species frequently coexist in streams and streambed pools, with A. raffrayi the more abundant and more frequent species, except at very high altitudes where A. pallidus dominated. Large proportions of the individuals of both species were teneral from September to January, whereas in May and June all but one specimen were mature. A. pallidus is polymorphic in the development of the hind wings, and at least some of the long‐winged specimens had well‐developed flight muscles. In this species reduced hind wings and small body size are seemingly correlated with high altitude.