106 



PERCENTAGE OF WEEVILS HIBERNATING SUCCESSFULLY. 



It is a very significant fact that of the 240 weevils taken from the 

 field at the middle of December, 1902, and placed in hibernation, 38, 

 or 15.8 per cent, passed, the winter successfully, while of the 116 

 weevils adult before November 15, 1903, only 1, or less than 1 per 

 cent, survived. It is evident that the weevils which pass the winter 

 and attack the crop of the following season are among those developed 

 latest in the fall and which, in consequence of that fact, have not 

 exhausted their vitality by oviposit! on or any considerable length of 

 active life. 



Naturally the percentage of weevils living through the winter will 

 depend largely upon favorable climatic conditions and the accessibil- 

 ity of suitable shelter. It would be utterly impossible to determine 

 this question under actual outdoor conditions, and our inferences 

 must be drawn solely from percentages found to survive under cage 

 conditions. In the laboratory tests referred to in the preceding topic 

 356 weevils were used. Of these, 210 were brought from the fields 

 at the middle of December, 1902. Among these weevils, 38, or 15.8 

 per cent, survived. The remaining 116 weevils were all adult after 

 September 25, 1902, and had been kept under observation in the 

 laboratory. One single weevil, adult November 12, was the sole sur- 

 vivor of this lot. Since the weevils brought from the fields in the 

 middle of December would be a correct average of those entering 

 hibernating conditions, we may disregard the laboratoiw-bred speci- 

 mens in drawing our conclusions. The conditions offered would seem 

 to have been favorable, and when this is the case out of doors it 

 appears that about 1 in 6 of weevils found in the field at hibernation 

 time may pass the winter successfully. This seems a very high per- 

 centage, but when we consider the numbers of hibernating weevils 

 often occurring upon young cotton in the spring it seems not improb- 

 able that during favorable seasons something like this percentage of 

 the weevils finding favorable shelter will live. Of course, the per- 

 centage finding* favorable shelter will be extremely variable, and it is 

 in reducing the number and accessibility of favorable locations that 

 the cotton planter has one of his very best opportunities to effect the 

 destruction of a multitude of weevils, and thus greatly reduce the 

 number which will emerge from hibernation and attack the crop of 

 the following season. With shelter removed, cold and changeable 

 weather will inevitably destroy many, and, in fact, most, of the 

 weevils which would otherwise survive. 



TIME OF EMERGENCE FROM HIBERNATION. 



Emergence depends largely, as has been already shown, upon the 

 mean average temperature prevailing. The presence of food does 

 not seem to affect it. In the season of 1903 for one month preceding 



