﻿INSECTS OF EASTERN TROPICAL AFRICA. 279 



Family Psychodidae. 



Genus Phlebotomus, Rond. 



Representatives of this genus were taken in Northern Rhodesia and Nyasaland, 

 which will shortly be described by Professor Newstead as a new variety of 

 P. mznutus, Rond. They were mostly taken at light, immediately after sunset, 

 in damp localities, and seemed but little inclined to bite. 



Family Tabanidae. 



This family includes by far the greatest number of African biting flies. These 

 insects are often exceedingly numerous, and during my last tour, 9,591 specimens 

 were collected, of which 3,649 were males. The period, however, when these 

 flies are on the wing is often a very short one, and in regions with well marked 

 wet and dry seasons, is usually confined to the former. 



Tabanidae generally become noticeable in large numbers at the beginning 

 of the rains, though, as I shall explain later, many species probably emerge from 

 the pupa some time before the first rains fall. In some species at any rate there 

 appears to be a second brood about the end of the rainy season, and in certain 

 Haematopota and Chrysops there would seem to be several broods in the year. 



In East Africa, in the country south of about 9° S. Lat., there is normally 

 only one wet season, which lasts from about November to April, May to October 

 being dry. The best months therefore for Tabanidae in Nyasaland and 

 Northern Rhodesia are November to January. A limited number also occur 

 throughout the rainy season up to the end of April or beginning of May. 

 During the cool dry weather of June, July and August practically no 

 Tabanidae are to be found, and they probably spend this period in their larval 

 stages. 



In the Luangwa Valley, North-Eastern Rhodesia, judging by my experience 

 there in 1910, many species, especially of Taba?ius, begin to emerge from the 

 pupa during September and October. They are, however, during this time but 

 little in evidence until the first rains fall at the end of October or beginning of 

 November. During this period, immediately before the rains, more particularly 

 in the genus Tabanus, the males were at least as numerous as the females, and 

 the latter seemed not to be much in search of vertebrate blood. They might 

 therefore be overlooked at this time, unless specially sought for. 



Like nearly all biting Diptera, these insects appear to be peculiarly 

 sensitive to climatic conditions. Different genera vary in the conditions of 

 sunshine, amount of humidity, etc., which influence the times at which they are 

 inclined to feed. A certain degree of humidity of the atmosphere, even if only 

 temporary, would seem to be an essential factor in impelling the females to seek 

 for vertebrate blood. During the extremely dry hot weather which is usual 

 before the rains break, it is remarkable how little inclined to bite the females of 

 most species seem to be. Thus during September and October 1910, in Northern 

 Rhodesia and Nyasaland, over two thousand individuals of some twenty-five 

 species were collected. These were almost entirely taken in the immediate 

 vicinity of water, either drinking at wet sand or mud, or resting on the reeds 

 and grasses near by ; a few of the males were also frequenting flowers. T here 



