BEHAVIOR OF SOME SOIL INSECTS. 173 



tages of carbon dioxide at a temperature of 18 to 19 C. and a 

 relative humidity of 75 to 95 per cent. In graph 12, with carbon 

 dioxide percentages of 4.0, 2.2, and o.o respectively, an Evarthrus 

 sodalis larva selected the air containing the largest amount of 

 carbon dioxide. The larva used in graph 13, with carbon dioxide 

 percentages of 7.2, 4.0, and o.o respectively, showed no marked 

 preference for either the carbon-dioxide air or the carbon- 

 dioxide-free air. In graph 14 an unknown species of larva 

 showed a decided negative reaction to air containing 9.0 per cent, 

 of carbon dioxide. No experiments were performed to determine 

 the time of death of the larvae in different amounts of carbon 

 dioxide. In general, however, for mixtures of the gas up to n 

 or 12 per cent, the larvae were not violently affected. In air 

 containing from about 7 to 12 per cent, of carbon dioxide they 

 were sluggish and inactive and appeared fatigued. In per- 

 centages below this they sometimes selected the air containing 

 the carbon dioxide and sometimes avoided it. They were not, 

 however, much affected, if any, by low percentages of the gas. 

 There was no violent squirming and twisting produced by the 

 carbon dioxide but it seemed to have a depressing effect. The 

 larvae were sluggish, inactive, and appeared exhausted. 



2. Adults. 



A . Controls. The behavior of the adults, both in the experi- 

 ments and in the controls, was more irregular than that of the 

 larvae. They moved quicker and did not have the blind tendency 

 to continue in the direction they were going if the conditions 

 became unfavorable. Graph 15 shows two ten-minute controls 

 for adults. The first ten minutes is the control for an Evarthrus 

 sodalis adult and the last ten minutes the control for a Patrobus 

 longicornis adult. Temperature 21 C. and no air flow. The 

 Evarthrus adults showed a uniform tendency to run from one 

 end of the cage to the other, while the majority of the other species 

 often ran hesitatingly about for a time and then settled down and 

 remained quiet, usually at one end of the cage. 



B. Reactions in Evaporation and Temperature Gradients. A 

 number of experiments were performed with different species, 

 but only a few can be given here. Graph 16 shows the reaction 



