Humidity selection by thermoregulating grasshoppers

Abstract

1. 1.|To make the most effective use of evaporative cooling, an insect must be in an environment of the lowest humidity. 2. 2.|To test the hypothesis that, at temperatures requiring evaporative cooling, grasshoppers were able to select such a favourable environment, we observed the selection of, and time spent in dry (RH ⩽ 5%) or humid (RH ⩾97%) alternative chambers of a shuttle box at a range of temperatures from 28 to 50°C, in two species, Schistocerca americana and Romalea microptera. 3. 3.|Below 45°C, both species tended to remain in the chamber in which they began the trial; above 48°C, they all selected the arid chamber. 4. 4.|These findings suggest that grasshoppers can select the environment best for maintaining their body temperature below lethal levels but do not necessarily mean that they can actually sense relative humidity.