﻿IN THE LUANGWA VALLEY, NORTHERN RHODESIA. 239 



Breeding. 



The hot dry season has had a very deleterious effect on the breeding of the flies, 

 as shown not only by a reduction in the numbers of pupae produced, but also by 

 the subsequent death of a large proportion of these. In the hotter months great 

 difficulty was experienced in keeping the stock flies alive. Kinghorn* has already 

 detailed the conditions under which the flies were kept and the method adopted, 

 so that no more need be said under this head. 



The full history of the pupae produced is given in the accompanying table. 

 The number of abortions is not included as a full record of these was not kept. 

 Abortions were most numerous during September and October, while in the cooler 

 months there were not many. The number of stock flies was roughly constant, 

 the small number of pupae obtained during September being due to the raid of 

 ants mentioned above. Flies freshly caught do not breed so well as those which 

 are accustomed to captivity. The mean temperature is that of the room in which 

 the flies were kept. The readings of the wet and dry bulb thermometers were 

 taken in the open air under shade. The approximate mean temperature to which 

 the pupae were exposed has been arrived at by averaging the mean laboratory 

 temperatures for the periods in which the pupae were obtained and those periods 

 following which could have influenced them. The table shows that as the 

 temperature rose from 67° to 85° the duration of the pupal life was reduced from 

 fifty-one to twenty-three days, and the accompanying diagram will illustrate the 

 ready response of the pupae to even slight changes of temperature. Without 

 direct experiment it would be impossible to estimate the relative influence of tem- 

 perature and humidity. Since however the humidity of the air to which the 

 pupae of November 1-15 were exposed was greater than that during the pupation 

 period of the October groups, it would appear to be the high temperature rather 

 than the low relative humidity that caused the death of the pupae. 



In conclusion I must express my indebtedness to Dr. Kinghorn, the Chief 

 Investigator of this Commission, for the use of some of the data of the pupation 

 periods, and for assistance in many ways. 



Ncjoa, N. Rhodesia, May 1912. 



Kinghorn, Bull. Ent. Res. II, p. 291. 



