20 HIBERNATION OF THE COTTON BOLL WEEVIL. 



Table IV. — Number of weevils under rubbish on ground at Dallas, Tex. 



The sum total of weevils found both on plants and on the ground 

 on November 22 shows an average of slightly more than 9,000 weevils 

 per acre, all of which were alive. On December 18 the number that 

 could be accounted for was between 6,000 and 7,000 per acre on the 

 same ground which had been previously examined. On the former 

 date more than two-thirds of the weevils were still upon the plants. 

 On the latter date nearly five-sixths of them were on the ground and 

 among those on the ground but 26 per cent were living. These fig- 

 ures show that between November 22 and December 18 a very large 

 mortality had occurred among weevils which had entered hiberna- 

 tion and especially among those which had sought shelter under rub- 

 bish upon the surface of the black-waxy soil of field A. 



There is some evidence indicating that there is normally a greater 

 mortality among the weevils hibernating at the surface of heavy 

 black soil than that occurring among weevils which hibernate on the 

 surface of sandy soil. The reason for whatever difference there may 

 really be in this mortality would seem to be quite directly attributa- 

 ble to the difference in drainage conditions in the two types of soil, 

 and to the characteristic adhesiveness of the black type. It is quite 

 likely that the difference is sufficient to justify different methods of 

 treatment for the two classes, but our knowledge of the constant 

 variations and the effective factors is not yet sufficiently complete to 

 justify us in making specific recommendations. 



TEMPERATURE CONDITIONS PRODUCING HIBERNATION. 



It is evident that the exact time at which weevils begin to enter 

 hibernation, and that at which the entrance into hibernation be- 

 comes complete, can be determined only approximately. The evi- 

 dence consists largely of observations showing the decrease in the 

 number of weevils which are active, the finding of weevils in a quiet 

 condition within various classes of shelter, the changes in activity of 

 weevils confined in cages, the cessation of feeding and of reproductive 



