160 CLYDE C. HAMILTON. 



Shelford and Deere ('13), except for the method of measuring 

 and controlling the rate of air flow. This is new and will be 

 described in some detail. The supply of air was secured from 

 the University high pressure supply and was reduced from about 

 80 pounds to 5 pounds by a Mason reducing valve, which gave a 

 constant pressure irrespective of the amount of air used. At 

 room temperature, about 70 F., the air had a relative humidity 

 of 1 8 to 20 per cent. The moisture was removed from the air 

 by passing it through sulfuric acid niters, then through a glass- 

 wool filter to remove any trace of the acid, a coiled aluminum 

 pipe to regulate the temperature, and finally to the apparatus 

 for controlling the rate of air flow. The sulfuric acid filters 

 consisted of six chloride jars, 18 by 3 inches, filled with moder- 

 ately fine pumice stone saturated with sulfuric acid. The medium 

 moist air and saturated air was passed through glass-wool filters 

 and then moistened by blowing it over or bubbling it through 

 water in wash bottles. By passing the air into the bottles through 

 glass tubes and regulating the height of the opening above the 

 water almost any per cent, of saturation could be obtained. 

 From the wash bottles the air passed through coiled aluminum 

 tubes for regulating the temperature and then to the apparatus 

 for regulating the rate of air flow. 



The experimental cage for observing the behavior and modi- 

 fication of the insects, and the glass tubes for testing their re- 

 sistance to evaporation and gases, were the same as those de- 

 scribed by Shelford and Deere ('13). The experimental cage 

 was 30 cm. long, 6.5 cm. wide, and 2.5 cm. deep. The glass tubes 

 were each 21 cm. long and 3.2 cm. inside diameter. The lower 

 third of each tube was filled with paraffin upon which sand had 

 been sifted while it was still warm. From each of the tubes the 

 air passed to a chamber containing a Livingston porous cup at- 

 mometer so that the evaporation could be recorded while the 

 animals were being observed. For testing the relative humidity 

 of the air two long chemical thermometers, graduated to 0.5 of 

 a degree, were inserted with the bulb end inside a glass tube 

 about 20 centimeters long and 2 centimeters in diameter, through 

 which the air was allowed to flow. The wet bulb thermometer 

 was provided with a wick which connected with a vial of distilled 

 water. 



