INFLUENCE OF CLIMATE 45 



little shade : the humidity of the island atmosphere 

 saved them from the heat that might have been fatal 

 on the mainland. 



Secondly, the hunger of females, as estimated by the 

 numbers caught, is very dependent upon the temperature. 

 Fiske proved to me in 1914 that the female percentage 

 is not an indication of the actual numbers but of the 

 hunger of the fly. Since the percentage figure varies 

 inversely each month with the temperature, as is shown 

 by the charts for Bugalla and Jinja, it follows that the 

 hotter the month the less the fly is inclined to bite. 

 Indeed, I have noticed on individual days that the fly 

 bites less during the hottest hours, and less on a brilliant 

 sunny day than when the sun's heat is tempered by thin 

 cloud. 



A further effect of climate was noted on Bugalla, 

 namely, upon the number of pupae that could be found 

 each month (see Chart IV). 



At the end of every month the boys visited certain 

 well known sites much liked by palpalis for its pupae, 

 and an average figure was obtained called " pupae per 

 boy " to indicate empirically the number found per 

 month. It is obvious that the total number found at 

 the end of each month must depend in part upon the 

 number of female flies, which is indicated, at least as 

 regards the number of hungry flies, by the *' female-boy- 

 hour " figure for the month. 



If the " pupae-boy " figure be divided by the latter 

 figure, the quotient may be used as a means of comparing 

 from one month to another the rate of reproduction, 

 bearing in mind that the times when the flies are hungriest 

 will thus appear as months when the reproduction figure 

 "pupae per female " is lowest. 



Thus, the average number of pupae found per boy in 

 the given time at the end of February was 187-3 ; the 

 average number of females caught per boy per hour during 



