18 



BULLETIN 926, U. S. DEPARTMENT OF AGRICULTURE. 



When the thermometer was wrapped in cool, green leaves it regis- 

 tered 89° F., but when inserted into a square and wrapped in green 

 leaves it registered 81°. 



The thermometer covered one-fourth inch by hot sand in the sun 

 registered 106.5° to 107.5° F. ; under one-half inch of sand it regis- 

 tered 99°, under 1 inch 95°, and under 1-| inches of sand 91°. 



Thus shallow burial of infested squares would merely give the 

 immature weevils more favorable temperatures and almost insure 

 emergence : while the sun-heated surface soil, even on this moderate 

 day. was heated very close to a fatal temperature. 



Tig. 8. 



-Outdoor insectary, Madison, Fla., wherq the records were secured to check 

 against the field records. 



Dr. Pierce then studied the temperature in the field breeding cages 

 and found in the oviposition cage an air temperature of 85° F., a soil 

 temperature in the sun of 108° to 108.5°, in the shade of the wire 

 screen 90° to 94.5°, and in the shade of the plant 92° to 95°. The 

 humidity in the cage was 71.5 per cent, wet bulb 85, while in the 

 open air it was 68.5 per cent, wet bulb 85.5. There is therefore very 

 little difference in the temperature in and out of the cage. 



The small wire-screen cages used to cover the squares during the 

 last two days before emergence were then measured. In the shade of 

 the plant the temperature was 94.5° to 96.5° F. and in the sun 103° to 

 106°. The cage, therefore, serves to mitigate slightly the intense heat. 



In the insectar}'' measurements were made in the breeding tumblers. 

 A temperature of 83.5° F. was recorded for the soil in the tumblers, 

 while above the soil the temperature was 86.5° F. Since the tumblers 

 were only moistened once during the hatching period, a temperature 



