CLYDE C. HAMILTON. 



of a Pterostichus stygicus adult to dry air at a temperature of 

 20.5 C. and an air flow of 13.3 liters per minute. The adult 

 showed a tendency to move about at first but soon became in- 

 active and remained quiet during the remainder of the experiment. 

 It was active and in good condition when the experiment was 

 discontinued. Graph 17 shows the reaction of a Pterostichus 

 corvinus adult to dry air at a temperature of 19 C. and an air 

 flow of 13.3 liters per minute. The adult did not show as 

 decided a reaction against the dry air as the adult in the previous 

 experiment but at the end of about eight minutes a preference 

 was worked out for the wet air. Graph 18 shows the reaction 

 of an adult of the same species to dry air at a still lower tem- 

 perature, 16.5 C., and an increase in the rate of air flow to 19.0 

 liters per minute. Although the adult was restless and uneasy 

 during the experiment, it showed little tendency to select the wet 

 air. 



To test the resistance of the adults to evaporation, three adults 

 were put in the glass tubes with air flowing through them at a tem- 

 perature of 21 C. at the beginning and 23 to 25 C. at the end, 

 and a relative humidity at the end of 30 per cent. In the tube with 

 an air flow of 13.3 liters per minute the adult died after 28 hours' 

 exposure, during which time 70 c.c. of water had evaporated 

 from the porous cup atmometer. In the tube with an air flow 

 of IQ.O liters per minute the adult was dead at the end of 30 

 hours, during which time 77 c.c. of water had evaporated from 

 the atmometer cup. In the third tube, with an air flow of 22.4 

 liters per minute the adult was dead at the end of 24 hours, during 

 which time 82 c.c. of water had evaporated from the atmometer 

 cup. 



C. Reaction in Ammonia Gradients. A few experiments were 

 performed with air containing ammonia to determine the reaction 

 of the adults to this gas. To obtain the gradients of ammonia 

 in the air it was bubbled through water containing different 

 amounts of the gas in solution. No quantitative determinations 

 of the amount of ammonia in the air were made. Graph 19 

 shoAvs the reaction of an Evarthrus sodalis adult to gradients of 

 ammonia at a temperature of 22 C. and a relative humidity of 

 98 per cent. In this instance the avoiding reaction against the 



