PREFACE 



Natural conditions annually reduce enormously the numbers of the 

 cotton boll weevil. Although no two seasons are exactly alike, never 

 more than a small percentage of the weevils in the fields in the fall is 

 permitted to survive until spring. In fact, winter is the most critical 

 season in the whole life history of the weevil. Any steps in control 

 of the weevil during the winter are therefore much more important 

 than those which can be taken at any other season of the year. To 

 destroy ten weevils in the winter is much better than to destroy many 

 thousands in the summer. The cotton boll weevil is now causing a 

 damage in the United States each year of at least $25,000,000. The 

 indications are that this amount will continue to be lost for some time 

 at least on account of the difficulties in control which will be encoun- 

 tered in the Mississippi Valley. For these reasons the Bureau of 

 Entomology has conducted careful investigations of the hibernation 

 of the weevil and presents the somewhat detailed results in this 

 bulletin. 



Until this time the hibernation of the boll weevil has been less 

 understood than any other phase of its life history. This was due to 

 the great difficulty in obtaining the necessary data and the fact that 

 the phenomena of hibernation are not necessarily identical in difi^erent 

 seasons. In fact, it will be seen from the following pages that there 

 have been very important dissimilarities between the years when 

 special observations have been under way. The necessary repeated 

 work in large cages in different localities has now been carried on and 

 extensive field observations have been made in various representative 

 parts of the infested area as to the natural situations in which the 

 hibernating weevils occur. As a result, the present bulletin will 

 make the life history of the boll weevil during the winter season at 

 least as well known as any other portion of its biology. 



In the work leading to this bulletin practical considerations have 

 always received primary attention. However, it has repeatedly been 

 shown that careful detailed investigations of injurious insects may 

 result in important suggestions for control that are not foreseen at the 

 beginning of the work. Therefore the topic of the hibernation of the 

 boll weevil has been investigated from every possible standpoint. 

 Its importance, as a critical period in the life history of a most injuri- 

 ous pest, has abundantly warranted this work. 



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