BIOLOGICAL COMPLEX. 39 



important in the control affected by climate, it should be considered 

 as one of the most critical times of the year for controlling the boll 

 weevil. When a sudden drop in the temperature below freezing 

 occurs in the month of November before a large proportion of the 

 weevils has entered hibernation, and while many are still immature, 

 an excellent control of the species can be obtained. As, however, 

 this is only an occasional occurrence, it can not be relied upon and 

 every measure possible should have been carried out to prevent the 

 weevils from going into hibernation at all. 



II. Hanging squares are the most important infested parts for the 

 work of parasites, and fallen squares in a similar degree for the work 

 of the predatory enemies. It has been demonstrated also that in 

 certain years the total control by all agencies is greater in hanging 

 squares than in fallen squares, and furthermore that in the more 

 humid States this condition is the prevalent one. 



III. It has been shown by examples that the total mortality of 

 the weevil can be increased in proportion as the number of hanging 

 squares in a given area is increased and likewise that the pro- 

 portion of parasites to weevils is increased. It is therefore recom- 

 mended that plant breeders attempt to develop varieties of cotton 

 which will retain the squares, but will also have the other desirable 

 varietal characteristics necessary for the production of an early 

 cotton crop. 



IV. The insect control of the boll weevil is dependent in a large 

 measure upon the operations of the farm and for this reason all those 

 field practices which have been included in the system of cultural 

 control of the boll weevil are further recommended as tending to 

 increase the insect control. 



PART II. BIOLOGICAL COMPLEX. 



In Part I of this bulletin one set of facts, composed of statistics, 

 was dealt with, and it was merely hinted that the causes of these con- 

 ditions were very complex. In this part is presented another series 

 of facts, even more significant than the first, but much more difficult 

 to present in a tangible manner. The study of these biological 

 factors received its first impetus when at Clarendon, Tex., in 1905, 

 Mr. C. R.Jones and the senior author were fortunate enough to leartu 

 the biologies of three species of weevils and to find that all these were 

 parasitized more or less abundantly by the same parasites as is the 

 boll weevil. It was already known that some of the parasites of the 

 boll weevil attacked other weevils, but the significance of this fact 

 had not been realized. 



