77 



for each generation. a As it has been found that the average period of 

 oviposition is about 5^ days, we must allow 24 days for the develop- 

 ment of the average adult and 18 more days for the female to deposit 

 one-half her eggs. Forty-two daj T s is therefore about the average 

 length of a generation; and we may thus count on an average of about 

 five generations between May 1 and December 1. In the northern 

 part of the weevil territory, where the season is shorter and the pre- 

 vailing temperature lower, probably only four generations would be 

 developed. 



There is no basis for the idea that there is a distinct hibernation 

 brood. The activity of the adults and the development of the imma- 

 ture stages is gradually retarded b} T the decline in temperature until 

 hibernation time arrives. Most of the weevils of the first two or three 

 generations have probably died, or then do so, while most of the adults 

 of later generations, having still considerable vitality, will go into 

 hibernation. It is certain that every generation preceding may have 

 some direct part in the production of weevils which shall hibernate. 

 All weevils which are still strong and health}^ when cold weather comes 

 on may be expected to go into hibernation, so that there can be no 

 special brood for this purpose. 



THERMAL INFLUENCE UPON ACTIVITY AND DEVELOPMENT. 



The influence of temperature has been frequently mentioned as an 

 important point, but it may be more clearly understood by collecting 

 some of the most important observations relating to it. A study of 

 this subject throws much light upon such questions as seasonal and 

 daily activity, the rapidity of development at various seasons, hiber- 

 nation, and the time of emergence from hibernation. The influence 

 upon development will be first considered. 



a One-third is nearer the correct fraction than one-half, since it has been found 

 that weevils deposit considerably more than one-half of their eggs during the first 

 half of their oviposition period. 



