116 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



trated this in the case of the yellow fever mosquito. In a 

 paper on the distribution of the yellow fever mosquito he had 

 decided that this species would be found throughout the 

 Tropical and Lower Austral life zones and the zone in the 

 southern hemisphere corresponding to the Lower Austral 

 Life Zone in the northern hemisphere, and he prophesied that 

 in lower austral regions where this mosquito is not found it 

 could undoubtedly establish itself when once introduced, pro- 

 vided the necessary water supply were present. Messrs. Dyar 

 and Knab, however, had recently shown him that there exist 

 regions in the Lower Austral Zone where the yellow fever 

 mosquito has undoubtedly been frequently introduced and 

 where it has not established itself, as, for example, in Southern 

 California. Here, in the opinion of Dyar and Knab, the low 

 temperature during night time has prevented the establish- 

 ment of the species, and in this conclusion the speaker agreed. 

 Winter cold also undoubtedly limits the northern distribution 

 of many forms which hibernate as adults, as, for example, 

 Schistocerca americana. 



In reply to a question by Mr. Quaintance about determin- 

 ing the mean temperature, Mr. Pierce stated that he had 

 made numerous computations of the mean of the curve on the 

 thermograph sheet by the use of a polar planimeter and found 

 that this mean corresponded to the fraction of a degree with 

 that obtained by averaging the daily maximums and mini- 

 mums. 



Dr. Hopkins said he found the records of the Weather 

 Bureau of no value in determining the laws in his subjects; 

 the local conditions are too variable, and he would recommend 

 experiments to determine the laws governing plants. 



Mr. Pierce replied that all insect development records should 

 be coordinated with thermohygrograph records taken on the 

 spot. He stated that the botanists have worked out the zeros 

 of effective temperature for different plants, and for different 

 functions of the same plant. 



Mr. Rohwer said that in Boulder, Colorado, the' tempera- 

 ture varied two or three degrees between the different sta- 

 tions there. The U. S. Weather Bureau has one station 

 there and the records from it did not agree with those made 



