354 Comparative Animal Physiology 



the desert locust Schistocerca,-^ and the grasshopper Gastrimargus^^'^^ show 

 body temperatures lower than air in warm dry air, but in warm moist air they 

 show temperatures higher than air. At low temperatures differences in humidi- 

 ty have little effect, and the body temperature may be slightly above the air 



Fig. 89. The highest temperatures at which insects can survive exposures for 24 hours, 

 under conditions of controlled atmospheric humidity. From Mellanby.*^^ 



temperature (dry-bulb). Some insects are hygroscopic, that is, gain weight in 

 a high humidity; under such conditions body temperature must rise above 

 air temperature. In the roach, evaporation increases at temperatures above 30° 

 because of increased permeability of the waxy layers of the cuticle (see Chapter 

 2). Most water loss is by way of the spiracles, and death in warm dry air may 



