80 



LABORATORY EXPERIMENT IN EFFECT OF TEMPERATURE UPON 

 LOCOMOTIVE ACTIVITY. 



The experiments here given were performed by Dr. A. W. Morrill. 

 In the absence of apparatus especially designed for such work, use 

 was made of a very simple device, constructed as follows: 



A thermometer was passed through a cork and inclosed in a test 

 tube, which in turn was placed within a hydrometer cylinder of suf- 

 ficient depth to inclose it (PI. XIII, fig. 49). 



Weevils were inclosed in the test tube with the thermometer, and 

 the temperature of the cylinder varied either by heating gently or by 

 the use of ice water. Starting with the thermometer at 64° F. , the 10 

 weevils inclosed were found to move slowly, half of them being quiet. 

 As the temperature was gradually raised the activity of the weevils 

 increased up to 105° F. When the temperature reached 95° F., or 

 over, the weevils were running up and down the tube. By filling the 

 cylinder with cold water the temperature was lowered to 86° F., at 

 which point the weevils began to cluster at the top on the cork and 

 were crawling slowly. By the addition of ice in the cylinder the tem- 

 perature was lowered to 59° F., at which point 5 weevils were sprawl- 

 ing on the bottom of the test tube or clinging to one another, 4 were 

 clustered on the stopper, while 1 was slowly crawling downward. At 

 50° F. 6 weevils at the bottom showed slight signs of life and 1 was 

 crawling slowly. At 45.5° F. slight signs of life were still shown, 

 while at 40° F. occasional movements only were noted. Upon the tem- 

 perature being raised weevils' began crawling as 50° F. was passed, 

 and at 64° F. all had left the bottom and were crawling upward. 

 Some recovered much more quickly than did others. 



The temperature was again lowered, this time by the use of salt with 

 ice. All movement ceased at 37° F. The cooling, however, was con- 

 tinued to 33° F., after which it was slowly raised to 42° F., at which 

 point movements began. 



In a general way these results agree quite closely with outdoor 

 observations. 



HIBERNATION. 



Even after frosts have blackened the foliage and squares and 

 entirely checked the growth of the plant, some weevils can be found 

 moving in a cotton field upon warm days. Weevils which are old and 

 nearl} T exhausted die as the cold weather comes on. Their vitality 

 has been expended in other ways and they do not survive the winter. 

 Those which are still vigorous and strong will continue to feed a little, 

 and females will occasionally deposit eggs so long as cotton remains 

 green. In southern Texas larvae and pupa3 which are in squares when 

 frost comes are not killed thereby, but slowly finish their development 

 if the weather is warm enough for any activity, and the young adults 

 thus developed may live the winter through without feeding. As 



