﻿IN THE LUANGWA VALLEY, NORTHERN RHODESIA. 235 



Habits. 



In the valley the fly becomes active at sunrise, if there is no dew, disappearing 

 during the hottest hours of the day, except in deep shade. Directly it becomes 

 cooler the fly recommences to bite and continues to do so till some time after the 

 sun has set. When a lamp was taken at night into the room where the captive 

 flies were kept they immediately became active. Individuals occasionally flew on 

 to our verandahs in the evening and attempted to feed by lamp-light. At Ngoa, 

 where the mornings are at present cold with heavy dews, the fly does not become 

 active till the sun has been up for two or three hours. They may be seen resting 

 on the trunks of trees and are very wary if approached. They continue to bite 

 throughout the day but are most troublesome between the hours of 4 and 5 p.m. 

 As a rule the tsetse disappear during a shower, but on one occasion when I 

 walked for an hour in heavy rain they continued to bite all the time. They bite 

 readily through one thickness of clothing and if no jacket is worn the shoulders 

 are badly attacked. However hot the weather this garment should always be 

 worn in fly country. It is advisable also to have the bottoms of the trousers 

 closed as the flies often enter and bite above the socks. Tight thin clothing is 

 much to be deprecated and the ideal clothing consists of boots, thick puttees and 

 loose knickerbockers. 



Proportion of the sexes. 



Much difficulty was experienced at first in obtaining sufficient females for 

 breeding purposes. Frequently only three or four females Avere brought in 

 amongst two or three hundred males. Later the boys were shown the differences 

 between the males and females and there was then no difficulty in obtaining a 

 sufficiency of the latter. The relatively small proportion of females that is 

 normally taken is a matter of great interest. In the laboratory the sexes are 

 bred in equal numbers, so that it is fair to assume that they are really equal in 

 nature. Several writers have drawn attention to the fact that the swarms of 

 tsetse which accompany a moving object leave it as soon as motion ceases.* 

 While this is certainly the case, yet flies which desire to feed do not leave a 

 standing animal and one is very frequently bitten when standing or sitting. The 

 majority of the swarm however are not desirous of feeding and may often be 

 seen settling on the cover of a machila,t though the helpless backs of the bearers 

 offer tempting opportunities for a meal. If the flies which actually bite are 

 caught they are found to be females as frequently as males, but the small propor- 

 tion of females that is caught normally shows that the swarm consists almost 

 entirely of males. An analogous case may be quoted. The vast swarms of 

 midges so often seen on fine evenings are known to consist entirely of males, and 

 directly a female joins the swarm it is mated and the couple drop from the dance. 

 With Glossina, as long as an animal is moving there is a probability of females 



* Montgomery and Kinghorn, Ann. Trop. Med. and Paras, Til, p. 325. Other writers have 

 made the same observation about G. palpalis. 

 f [A kind of sedan-chair — Ed.] 



