HIBERNATION. 97 



emerge. These might emerge upon warm days following the colder 

 weather, but in the absence of a fresh food supply would soon die. 

 In the fall of 1903 Prof. E. D. Sanderson, in an examination of 700 

 squares at the middle of November, found 79 eggs, which means that 

 11 per cent of the squares contained eggs. In an examination of 

 1,600 squares he states that 366 larvae were found, showing that about 

 23 per cent of the squares contained larvae at the time of entrance 

 into hibernation. 1 Some stages may survive in squares for a short 

 tune after the freeze, but there are few records of weevils entering 

 hibernation as immature stages in squares and surviving to emerge 

 therefrom in the spring. These stages are therefore unimportant 

 from an economic point of view. 



With immature stages entering hibernation in bolls, the case is 

 quite different from that in squares. Very large numbers of weevils 

 enter upon the period of hibernation as immature stages and during 

 many seasons, especially in the southern part of the State, a large 

 percentage of these complete their development, and many survive 

 until time for their emergence in the spring. Immature stages in 

 bolls have been found alive at Victoria, Tex., as late as February 17. 



TIME OF ENTERING HIBERNATION. 



Hibernation begins when the temperature reaches a point between 

 60° and 56° F. The exact point will be higher with a high percentage 

 of humidity and lower with a low percentage of humidity. 



According to the observations of Messrs. Newell and Dougherty. 2 

 at Mansura, La., in 1908, entrance into hibernation began on October 

 28. The mean temperature for 10 days preceding that date was 

 63.7° F., but the minimum dropped from 46° to 31° F. on the day the 

 weevils began to enter into hibernation. 



The action of the weevils in securing shelter from approaching 

 cold is instinctive rather than intelligent. It is probably true that 

 they have no such sense of sight as we commonly understand from 

 the use of that word and that then selection of shelter is not at all 

 guided by that sense. We mean by this that a weevil on a cotton 

 plant can not see at any distance shelter which might be attractive 

 to it and thereupon fly from the plant to the shelter. Cold nights 

 with a temperature between 40° and 50° F., succeeded by warm 

 still days, such as occur commonly hi the fall, seem to stimulate the 

 weevils to an unusual activity both in flight and in crawling. It 

 seems possible that they have an instinctive knowledge of the approach 

 of temperature conditions from which they must secure shelter, but 

 it is also true that many weevils remain active upon plants for some 

 time after the plants have been destroyed by frost and frequently 

 until several weeks after other individuals have entered hibernation. 

 In speaking of entering hibernation, therefore, we mean the entrance 

 of the weevils upon a period of comparative if not complete inactivity. 

 Their action in securing shelter is gradual and governed primarily 

 by the degree of protection from the cold which they may receive. 

 If early in the season a weevil accidentally finds shelter which gives 

 it exceptional protection from the cold it will likewise be exception- 

 ally protected from heat and therefore less likely than are other less 



1 Bull. 63, Bureau of Entomology, U. S. Dept. of Agriculture. 

 a Cir. 31, Lousiana Crop Pest Commission, p. 170. 



28873°— S. Doc. 305, 62-2 7 



