On the origin of the wet-season form of Zonocerus variegatus (L.) (Orth., Acrididae) in southern Nigeria, with some biological notes

Abstract

Previous reports and field observations at Ibadan and in northern Nigeria have established the occurrence of a dry-season form and a wet-season form of Zonocerus variegatus (L.). The wet-season form in the savanna areas of northern Nigeria is shown to be virtually identical with that from southern Nigeria on the basis of breeding seasons, habitat and morphometrics. Morphometrics show the wet- and dry-season forms to be distinct. It is suggested that the dry-season form in the wet rain forest zone spread into the dry savanna areas giving rise to a wet-season form adapted to the different climatic conditions. The increasing occurrence of the wetseason form in the south probably represents a re-invasion by the northern wetseason form.