Central Saharan populations of Locusta migratoria cinerascens (Orthoptera: Acrididae) in irrigated perimeters: is it a recent colonisation event?

Abstract

Locusta migratoria cinerascens became a potential pest in irrigated cereals under pivots, in the Touat region (Algerian Central Sahara), since the indication of the first crowding in June 1994. Morphometrics and bioclimatic approaches revealed the homogeneity between North and South Algerian populations, suggesting a recent colonisation of Central Sahara, aided by the development of large acreage perimeters. We studied the populations of this acridian from 1995 to 2004 and show that they belonged to the solitarious or transiens phase and never reached the gregarious one. The absence of this last phase is discussed in the light of heterogeneous densities observed in the successive generations.