Oviposition Site Selection by the GrasshoppersMelanoplus borealisandM. sanguinipes(Orthoptera: Acrididae)

Abstract

Female grasshoppers can affect the fitness of their offspring through their selection of oviposition sites. Successful embryological development depends on suitable temperature and moisture levels, factors which may vary greatly on a fine scale in natural environments where grasshoppers occur. Knowledge of parameters defining acceptable oviposition sites can provide guidelines for habitat manipulations that reduce the availability of such sites. This paper compares oviposition-site selection in two species of grasshopper from Alaska, Melanoplus borealis and M. sanguinipes, and a population of M. sanguinipes from Idaho. Laboratory experiments did not detect any differences in preferred substrate temperature among the groups of grasshoppers. In field cages containing a choice of different ground covers (bare ground, single clump of grass or turf), M. sanguinipes from Idaho were less selective in terms of the distribution of egg pods among the different cover types, whereas both M. borealis and M. sanguinipes from Alaska deposited the fewest egg pods under the turf. Results suggest that differences in oviposition behavior between the grasshoppers from Idaho and those from Alaska may stem more from differences in the above-ground physical structure of the vegetation, than from differences in responses to below-ground temperature.