BIOLOGY OF THE MEXICAN- COTTON BOLL WEEVIL. 17 



The development of the weevil is retarded on the plant, and more 

 so on the ground, and accelerated in the insectary. The outside soil 

 is either too hot or too cool and damp, while the insectary maintains 

 a more even condition, warmer than the plant and cooler than the 

 ground. 



If one feels of a leaf or square on a hot day he immediately receives 

 a sensation of coolness. If he lays his hand on the sand in the 

 shade of the plant it feels cool and damp, and if he lays the other 

 hand on the sun-heated sand he experiences a sensation of burning. 



Dr. Pierce made a series of temperature measurements on June 21, 

 1919, in a period of less than 2 hours (from 10 to 12 " daylight-saving 



Fig. 7. — The field hatchery, Madison, Fla. 



time," or 9 to 11 astronomical time) in which the air temperature 

 about 2 feet above the ground was 88.5° to 89.5° F. 



The humidity by sling psychrometer was 68.5 to 69 per cent, by 

 wet bulb 73.5. 



The temperature of the sandy soil in the sun was 106.5°, 111°, 111°, 

 and 115° F. at different readings. Once in a while clouds shaded 

 the earth. 



In the shade of the cotton plants the temperature of the sandy soil 

 was 92.7°, 93°, and 94° F. at different readings; in other words, the 

 shade of the cotton plant reduced the temperature 14°, but the air 

 temperature was 4° or 5° cooler than the sand under the plant. 



Behind the involucre of the square on the plant the temperature 

 was 88° F., and next to the stem of the plant, 2 feet above the ground, 

 it was the same. 



16073°— 21 3 



