22 SENSATIONS PRODUCED BY TSETSE BITE. 



sharp and needle-like, leaves no irritation, and it invariably 

 chooses those parts that are shaded from the rays of the sun — 

 such as under the brim of the hat, behind the ear, neck, and 

 under the throat if not protected by a beard. If allowed to 

 suck itself full, its body becomes so distended that it has the 

 appearance of a small unripe purple grape [see Fig. 6], and it is 

 unable to fly more than a few yards before settHng. Its proboscis, 

 which is very slightly curved downwards, is attached to the head 

 horizontally, and is protected by a sheath divided longitudinally. 

 "When it bites the proboscis is T'ertically lowered, whilst the double 

 sheath is retained in its horizonal position." The " sheath " here 

 referred to is formed by the palpi, which in the normal position, 

 when the proboscis is not in use, are applied to the latter so 

 closely as to conceal it and give the appearance of a single organ. 



According to Chapman [30] the Tsetse " assails different 

 animals in their most defenceless parts : a man behind the back 

 between the shoulders, and an ox on the back or under the 

 belly ; a horse in the same places, and inside the nostrils ; and a 

 dog on the forehead, &c." Colonel Bruce writes : * — " It affects 

 in hoi'ses the legs, especially in the region of the fetlock, and on 

 being detached from its position by the vigorous kick the horse 

 gives, will only rise a few inches and again settle near the same 

 spot. After the initial prick there is no irritation, and the 

 animal will stand quietly while the fly has its feed." Stanley, 

 however [45], describes an occasion when, owing to the bites of 

 Tsetse, " Hoi-ses and donkeys streamed with blood, and reared 

 and kicked through the pain " : and Rankin [79], in his account 

 of the experiment made to test the value of elephants as baggage- 

 animals in East Africa, states that, "The fly swarmed on the 

 elephants till blood trickled down their flanks in a constant 

 stream." The writer adds that although the elephants " endured 

 this " for days, without subsequently showing any " prolonged 

 signs " of Tsetse-fly disease, they " seemed pained and distressed 

 during the infliction " of the bites. 



The time taken by the Tsetse in sucking its fill is remarkably 

 short. According to Andersson [20] it is but " a few seconds " ; 

 •while Colonel Bruce says f : "It is astonishing with what 

 rapidity the flies fill themselves ; in as small a space of time as 

 twenty or thirty seconds a fly will become swollen out like a 

 balloon with bright red blood " [see Fig. 6]. 



Contrary to what is the case among horse-flies (Tabanidte), of 



* Cf. Chapter YII., Appendix A, p. 272. f Ibid, p. 271. 



