SPATIAL VARIATION IN DIURNAL SURFACE TEMPERATURES AND THE DISTRIBUTION AND ABUNDANCE OF AN ALPINE GRASSHOPPER

We studied the influence of spatial differences in diurnal surface tem peratures due to topography on an alpine grasshopper (Aeropedellus cla vatus). Temperature measurements on east- and west-facing alpine dry m eadow slopes on Niwot Ridge in Colorado demonstrated a significant dif ference in diurnal surface temperatures between the two slopes through out the growing season. A. clavatus body temperature was found to be h ighly correlated with nearby shaded surface temperature, and individua l grasshoppers enclosed on the two slopes had significantly higher rel ative growth rates on the warmer east slope. Temperature effects were manifest at the population level as well. A. clavatus was significantl y more abundant on the east-facing than on the west-facing slope, desp ite similar vegetation in both areas. This study contributes to our un derstanding of the myriad of factors governing insect distribution and abundance by attempting to integrate the physiological and ecological , abiotic and biotic, influences on both individuals and populations.