79 



The investigations upon G. morsitans made in Rhodesia by Messrs. 

 R. W. Jack and LI. Lloyd show that this Tsetse-fly is most active during 

 mild weather ; mists, strong winds and cold weather, as also, too, 

 intense heat, do not suit it at all. As a general rule, except when 

 there is a mist, G. morsitans is ready to feed immediately after sunrise, 

 retiring to cover during the hottest hours of the day and recommencing 

 to bite in the afternoon, when it is cooler. The fly may sometimes 

 continue to bite after sunset when the nights are warm ; during 

 showers of rain it usually disappears. 1 



As regards G. longipalpis, Dr. Roubaud (H9a) says that in Dahomey 

 this species, like G. palpalis and G. tachinoides, lives chiefly at the 

 expense of wild animals, and accompanies big game in its movements ; 

 paths recently trodden by hippopotami and elephants are favourite 

 haunts of this Tsetse-fly. 



With regard to times when greatest activity is displayed by G. 

 pallidipes, observations by various observers (Leese, Croveri, Schwetz) 

 in different parts of Africa have already been recorded (see p. 53). 

 Writing of this species as observed by him in the coastal regions of 

 Kenya Colony, the late Captain R. B. Woosnam remarks (165) : 

 " From personal experience I can testify to the fact that G. pallidipes 

 feeds greedily during the whole night, but, in my experience, not during 

 the daytime." This statement is not borne out by the other writers 

 referred to, though Leese says that the fly " sometimes bites in the 

 dark." 



"G. brevipalpis," writes Austen, " is active and desirous of feeding only 

 at two periods of the day early in the morning before 8 o'clock, and 

 in the evening from about 4 p.m. onwards. The intervening hours, 

 from 8 a.m. to 4 p.m., are passed by G. brevipalpis in concealment, 'under 

 leaves of bushes or in the grass, always near the ground' (Sanderson), 

 or low down on the trunks of trees, two or three feet from the base. 

 While thus resting motionless the flies are difficult to discover and 

 capture, and ' their presence would be entirely unsuspected ' (Sander- 

 son) ; at Kaporo, near the north end of Lake Nyasa, Davey found that 

 they preferred to rest on ' trees surrounded by creepers and undergrowth, 

 and hid away in crevices in the bark or under the origin of branches.' 

 Both Davey and Sanderson observed a pair in coitu on a tree-trunk, 

 in the one case at midday, in the other at about 5 p.m. ; attempts 

 to find the pupae of this fly by digging round the bases of various trees 

 were, however, unsuccessful. Davey states that about 4 p.m. G. 

 brevipalpis ' seems to emerge from its hiding place and settle on dried 

 leaves, sticks or dust on paths, apparently lying in wait for a meal ' ; 

 the same writer adds that he has noticed that ' game, on its way to 

 water in the evening, often stands for a time on emerging from the 

 forest on to a path, and would thus afford the fly an opportunity for 

 feeding.' According to Davey, G. brevipalpis as a rule ' seems ready 

 to bite human beings in the evening, but it does not set to work with 

 the rapidity and voracity that G. morsitans often exhibits.' When 

 feeding captive flies, Stuhlmann finds that the insects generally wait 

 for a while before deciding to suck ; they then, however, drive in the 

 proboscis with great quickness, and the abdomen usually becomes 



1 On several occasions Dr. Bequaert was bitten by G. morsitans at night, 

 when it was quite dark ; on the other hand he states that, in Katanga, the 

 general experience is that rain, even when fairly heavy, never prevents this insect 

 from coming out and gorging itself with blood. 



