ISO CLYDE C. HAMILTON. 



The increased temperature may have affected the larvae by 

 increasing their activity and metabolic processes, thus requiring 

 a larger amount of air. If this air is dry, we can understand 

 why the larvae are more sensitive to dry air at the higher tem- 

 peratures. On the other hand, if the temperature is lowered, 

 their activity and metabolic processes are decreased, thus re- 

 quiring a smaller amount of oxygen. In temperatures of 24 

 to 26 C. and above, the larvae were often depressed, less active, 

 and did not respond to the dry air so sharply. This may have 

 been due to the fact that the temperature was increased above the 

 point where their maximum activity occurred and that above this 

 point an increased temperature had a depressing effect. In 

 those experiments, in which the larvae had been subjected to 

 freezing weather for a number of days, the temperature at which 

 the larvae avoided the dry air the best was lowered from about 

 22 C. to 16 C. It was also noticed that larvae collected early in 

 the fall withstood high temperatures much better than those col- 

 lected later. 



The adults behaved somewhat similar to the larvae in the 

 experiments. They were more resistant to dry air and did not 

 have the blind tendency to keep going ahead when the conditions 

 became unfavorable. They often stopped and investigated 

 the dry air, apparently sensing it with their antennae. Their 

 greater resistance to evaporation and temperature is natural, 

 since they are usually found on the surface of the soil or near it, 

 and are thus subjected to higher temperatures and drier air. 

 Their increased chitinization of the body is also a greater pro- 

 tection from evaporation from the body surface. 



The reaction of the larvae and adults to carbon dioxide is not 

 surprising when we consider their habitat and the amount of 

 carbon dioxide found in the soil. No analyses of the moisture 

 or the amount of carbon dioxide in the soil were made, but taking 

 the figures available, the amount could not have been much below 

 4 per cent., which was selected by the larvae in the experiments 

 and which is probably their optimum. Insects are much more 

 resistant to carbon dioxide than are warm-blooded animals and 

 fishes (Shelf ord and Powers, '15) and can use practically all of 

 the oxygen from a given quantity of air. This has been shown 



