Dimorphism in the Flying Wings of a Species of Water Beetle, Agabus Bifarius (Kirby) (Coleoptera: Dytiscidae)1

Abstract

The ability to fly to new waters is a necessity for those species of water beetles (Hydradephaga and Palpicornia) inhabiting ephemeral ponds and streams. One is not surprised to find that flightless species are rare; Sherman (1913) has stated that the Nearctic dytiscid Agabetes acuductus (Harris) is without wings, but he may have intended to refer to Agabus bifarius (Kirby), since those acuductus which I have examined are all fully winged. According to Guignot (1933) the two species of the rare dytiscid genus Siettitia Abeille de Perrin, are “complètement aptères,” and are known only from deep wells in the south of France. J. Balfour-Browne (1939) has described a new genus and species of hydrophilid from Lake Tanganyika, in which the wings are reduced to mere functionless slips.