OF WASHINGTON, VOLUME XIII, 1911. 115 



treatment except during the short period when the new 

 growth of the host tree is starting, dates being of no value. 



Mr. Quaintance said that such laws may govern native in- 

 sects, but that in the case of introduced insects and such as 

 the codling moth, Conotrachelus t etc., temperature conditions 

 sometimes affect the insects that do not seem to affect the host. 



Dr. Hopkins replied that cultivated plants are not reliable 

 as guides in any locality, but that native forest trees (white 

 oak, tulip, etc.) should be considered. 



In reply to Dr. Hopkins' s remarks about phenology Mr. 

 Pierce stated that in the case of the boll weevil the develop- 

 ment of the host plant had absolutely nothing to do wjth the 

 emergence of the adults from hibernation. They emerge 

 during a period of three or four months and in accordance 

 with the accumulation of effective temperature in their hiber- 

 nation shelter. 



Mr. Cushman remarked that in connection with the climatic 

 effect on the boll weevil he had made a series of interesting 

 observations at Tallulah, Louisiana. In 1909 the winter was 

 warm and open, the weevils were out early and numerous, 

 the weather hot and moist, .stimulating rapid development of 

 the cotton plants. A change then came to very hot, dry 

 weather, which controlled the weevil so that a cotton crop 

 was made. The following year the reverse conditions pre- 

 vailed, but with the same effect. The winter was cold, result- 

 ing in a small survival, and was followed by a long, cold spring, 

 so that many weevils that had hibernated successfully died. 

 In May warm weather set in, the cotton grew rapidly, and the 

 weevils multiplied rapidly, so that by the end of the season 

 they had done practically the same amount of damage as in 

 the preceding season. Thus we have opposite conditions giv- 

 ing the same results. 



Dr. Howard stated that the results of Mr. Pierce' s work 

 were very significant. It is clear from the study of certain 

 insect forms that Merriam's summation of mean daily temper- 

 atures during the active season will not hold perfectly as the 

 controlling influence in distribution. Extremes of temperature 

 must be considered, especially extremes of cold. He illtis- 



