34 



paring the dates upon which the maximum emergence was known to 

 hnxe taken phice at different points in different years with a curve 

 of the mean monthly temperature for that year and the normal mean 

 monthly temperature for a series of years, it was found that such 

 was not the case. In some years the time of maximum emergence 

 was before the normal date at which the mean daily tenijXM-ature 

 became 78°. and in others later, depending upon the departure from 

 normal of that individual season. But the date of maximum emer- 

 gence did not depart from the normal theoretical date upon which 

 the mean daily temperature becomes 78° to the same extent as the 

 departure from normal Avas indicated by the mean monthly tem- 

 ]5erature curve for that year. The temperature may have reached 

 78° on June 1, for instance, where nominally it would have reached 

 that point jNlay 1, and still in that year the Aveevils emerged in maxi- 

 nunn numbers but a few days after the normal time. Sufficient 

 accurate data are not at present available to make a positive statement 

 as to what governs this date of maximum emergence, but, from all 

 data available and from a careful study of the temperature curves, 

 I wish to offer the following hypothesis, which I believe will be found 

 to come very close to determining this date and i)ossibly that of other 

 insects hibernating as adults." 



The date of maximum emergence from hibernation, or the date of 

 oviposition, will depart from the normal date — which for the boll 

 weevil may be considered the date when the temperature reaches 78° 

 F. or thereabouts — by the amount of the accumulated difference in 

 temperature between the normal dail}^ mean and the daily mean for 

 that year; or we might term it the accumulated departure from nor- 

 mal for that year during the period commencing one month prior to 

 the point of departure of the yearly line from the normal after the 

 ]ioint of first emergence and the date upon which the total accumulated 

 temperature for that year will equal the amount of accumulated 

 temperature in the normal year between the first date of this period 

 and the date of maximum emergence.'' 



The writer proposes to make studies of otlier insects to determine wlietlier 

 any genenil laws may be defined upon this point, and will be glad of any coop- 

 eration possible from others, as observations at several points distant from one 

 anoflier are necessary to make such work of value. 



b It seems desirable to insert a figure illustrating the hypothesis proposed, 

 as was done with drawings before the Association. For this the normal 

 monthly mean temperature curve for Victoria, Tex., and the monthly mean 

 temperature curve for the same place for 1904 have been selected. The figures 

 are those of the United States Weather Bureau. In platting the curves we 

 have used the ISth of the months for which the mean temperature is given. 

 I'he " mean monthly temperature " as reported is the average for the whole 

 month. It is evident that in most cases the 1.5th of the month would more 

 correctly approximate thiij temperature than the oUth, upon which date it is 



