Thermal capacity of different colour morphs in the pygmy grasshopper Tetrix subulata

I examined the relative importance of colour pattern, body size and shape for thermoregulation by experimentally subjecting adult female Tetrix subulata belonging to four different colour morphs (black, striped, brown, and white) to augmented irradiation levels. The results revealed significant variation in temperature excess (i.e., the difference between ambient and body temperature) among colour morphs, with black individuals having a mean temperature excess 49% greater than that of white individuals. Temperature excess was not significantly influenced by overall body size (measured as principal component 1 (PC1)) but increased with increasing values of PC2, suggesting that stout bodied individuals attained higher body temperatures than did individuals with low body mass relative to surface area. These results show that coloration may play an important role in determining body temperatures of grasshoppers exposed to direct irradiation, and suggest that reproductive females may be able to maintain higher body temperatures than non-reproductive females and males.