Graminivory abandonment gradation among two sub-species of Chorthippus binotatus (Acrididae : Gomphocerinae): descriptive and experimental approaches

Chorthippus binotatus is a west mediterranean species with 6 sub-species in France (DEFAUT, 1999). We focused on Limousin populations of the binotatus sub-species and on a Pyrenean population of the moralesi subspecies. Alime ntary diets, behaviour and labrum sensilla of this 2 sub-species were studi ed and compared with other species of Chorthippus. The sub-species binotatu s is the only locally monophagous species in Limousin region: it only feeds on (Ilex minor flowers and stems. The other species of Chorthippus from th e same places are graminivorous. The sub-species moralesi population have a mixed alimentary diet : Graminae and a Genistae. This sub-species is halfw ay between studied graminivorous species and monophagous Limousin populatio ns of the sub-species binotatus. The labrum studies show that the sub-speci es moralesi have intermediary characteristics in the number of sensilla. Le arning characteristics of the sub-species moralesi for the host plant can b e compared to the behaviour of the sub-species binotatus.