Food and Habitat Preferences of Melanoplus sanguinipes and Aulocara elliotti (Orthoptera: Acrididae) on Disturbed Rangeland in Southern Idaho

Food habits of Melanoplus sanguinipes (F.) and Aulocara elliotti (Thomas), confined to cages containing crested wheatgrass, Agropyron desertorum (Fisch. ex Link) Schult.; cheatgrass, Bromus tectorum L.; and assorted forbs were examined in May, July, and August by microhistological techniques. Habitat preferences were determined by sampling the density and species composition of grasshoppers and the aboveground plant biomass at 44 locations during early July 1990. In May, caged A. elliotti consumed crested wheatgrass and cheatgrass in proportions equal to their relative availability. In July, A. elliotti fed mainly on crested wheatgrass. M. sanguinipes fed mainly on cheatgrass in May. In July and August, forbs comprised the major portion of the diet. Observed habitat preferences were consistent with predictions based on the food preferences of the two species. Density of M. sanguinipes was positively correlated with aboveground biomass of forbs and annual grasses. Density of A. elliotti was positively correlated with crested wheatgrass biomass and percent bare ground. The results indicate that rehabilitation of annual rangelands with crested wheatgrass can potentially affect the local distribution and abundance of these grasshopper species, possibly by altering their food resources.