TEMPERATURE REGULATION BY EVAPORATIVE COOLING IN A DESERT GRASSHOPPER, CALLIPTAMUS-BARBARUS (RAMME, 1951)

1. We examined the desert-dwelling grasshopper, Calliptamus barbarus, to determine whether it used evaporative cooling, and if differences e xisted in the use of evaporative cooling between the small males and l arger females. Male C, barbarus are the smallest grasshoppers tested f or their use of evaporative cooling. 2. Calliptamus barbarus use evapo rative cooling at high ambient temperatures to keep their body tempera ture below lethal levels. This has been shown in insects such as cicad as, bees and other grasshoppers. Maximal water loss rates for C. barba rus are similar (8-10% of body mass per hour) to those of other grassh oppers. 3. Male C. barbarus weigh 370 mg on average, and are 20% of th e females' mass. At low ambient temperatures males evaporated 13.31 +/ - 1.14 mg water/h (n = 12), a similar rate to that in females, who eva porated 17.53 +/- 2.03 mg water/h (n = 29), but a considerably greater fraction of body mass per unit time. At high ambient temperatures, th e males lost less in absolute terms, but a similar amount relative to body mass. The differences are partially accounted for by scaling effe cts, but for the most part, the reasons for these differences are uncl ear. They may be linked to differences in ventilatory patterns between males and females or differences in cuticular permeability, the two m ajor pathways of water loss in insects. Copyright (C) 1996 Elsevier Sc ience Ltd.