GLOSSINA INVESTIGATIONS IN NYASALAND. 



45 



In this series the females form 28 per cent, of the total captures, and the figures 

 demonstrating that a relatively greater number of females are abroad during the 

 hot hours lends support to the argument, which is further borne out by a little evidence 

 tending to show that females may be taken in greater numbers in the ordinary wav 

 on the outskirts of the fly areas. Captures were effected in two localities on the same 

 days by an equal number of boys, two in each case, the flies being abundant at one of 

 these places (west of the road) and always scarce at the other (east of the road). 

 The results are tabulated below : — 



The proportion of females in the total captures works out in the first case at nearly 

 14 per cent., and in the second at 4 per cent. 



The sum of evidence therefore goes a long way towards establishing what becomes 

 of the missing females, and I am convinced that were it possible to include the females 

 which one so often finds alone at breeding places, equality would be attained. 



The following is the suggested intei-pretation of the facts observed :— The males, 

 most of which are already replete, attend man largely to await the arrival of females 

 coming to feed, hence the inequality in numbers in ordinary captured series ; for 

 whereas the males have a double object, the females have that of feeding only. On 

 arrival the female may be secured by one of the males, or if pregnant, may be driven 

 away in its endeavours to escape their attentions, then settling near by and renewing 

 its attempts to feed from time to time. Having fed, it retires to the shaded recesses 

 of large trees or to breeding places more or less remote from where the flies happen to 

 be massed at the time, its object being to keep free from the males. As there is so 

 great an increase in the numbers of the females taken off the trees and by other special 

 collecting methods, it is practically certain that the sexes exist in the same area in 

 equal numbers in accordance with the expectation from laboratory results. 



