﻿INSECTS OF EASTERN TROPICAL AFRICA. 281 



In the case of some species of Haematopota and Chrysops which frequent open 

 short-grass country, both sexes, but more especially the males, may be found in 

 enormous numbers on the grassy land near the water in which they would appear 

 to have bred. In such species large broods of apparently freshly emerged 

 individuals are as likely to be found in the middle or even at the end of the wet 

 season as at the beginning. 



Many species of Tabanidae are certainly attracted by sweet substances, 

 whether honey or the " honey-dew " secreted on plants by such insects as 

 Coccidae and Aphidae, this being especially true of the males. When near 

 Lake Kioga, in August 1911, I captured very large numbers of many specimens 

 of Tabanns, males being in the majority, apparently feeding on some sweet sub- 

 stance on the cotton plants of which there were fairly extensive plantations. 

 The flowers of many flowering shrubs are very attractive to these insects, 

 particularly those of the subfamily Pangoniinae. 



With reference to the interesting note from Dr. J. W. Scott Macfie, published 

 in the last part of this Bulletin (p. 223), regarding his capture of Tabanidae on a 

 tree infested by Coccids, attention should be called to two points. Firstly, 

 the predominance of the males, there being 34 out of 60 individuals ; and 

 secondly, his statement, " It is noteworthy that my pony, tethered not 20 yards 

 away, was quite unmolested by flies at the very times when I was catching con- 

 siderable numbers on this tree." 



This is precisely in accordance with my own experience, which is that when- 

 ever the males are at all numerous both sexes will be found either feeding on 

 sweet substances or drinking at damp sand, and the females do not show any 

 desire for vertebrate blood. Though further evidence and more systematic 

 observations are required, I think it is very probable that female Tabanidae will 

 be found to feed on blood only during a certain period of their imago state. This 

 period seems to be subsequent to pairing and to the death of the male individuals, 

 and most probably (though I have no actual evidence of this) before oviposition. 



Since this period when the females, at least in the case of Tabanus, are in 

 search of vertebrate blood appears also connected with some degree of atmo- 

 spheric humidity, it would be interesting to know exactly when, in relation to the 

 seasons, Dr. Macfie made his observations. From my own experience I should 

 expect it to have been shortly before the onset of the rains or, less probably, 

 during a dry interval in the rainy season. 



The males of those species which frequent forests are usually extremely difficult 

 to obtain, since the general conditions of humidity make it improbable that the 

 insects will be found drinking, even if the favoured spots could be located. Though 

 occasional individuals are to be found sheltering on the underside of leaves of 

 shrubs, flowers which are attractive to them offer the only reasonable prospect of 

 success. 



For some reason, which is not quite clear, canvas, either in the form of a tent 

 or stretched on the ground, in the latter case particularly if damp, is peculiarly 

 attractive to many Tabanidae and some Haematopota. I have observed only 

 females to be thus attracted, and what the object of their visits may be is 

 not obvious, since they seldom bite. I am inclined to think that the tent is 

 attractive as affording shade. Species of Tabamis, at least, seldom enter a tent 



