DB. J. KIRK ON THE TSETSE FLY OF TEOPICAL AFRICA. 155 



degree lost its firmness, and the lungs at base were engorged. 

 The first symptoms appear commonly within four days, but this 

 varies with the number of flies and the season of the year. 

 Natives report that cattle bitten die in greatest numbers before 

 the rains, or when they set in, and that some animals will linger 

 on until then ; that having passed a fly country you do not know 

 the full amount of loss until the rainy season has begun. 



The number of flies sufficient to kill an ox has been variously 

 estimated : Vardon speaks of ten or a dozen ; Mr. Oswell of three 

 or four ; Livingstone thinks that not a score of flies were on his 

 oxen. In the absence of direct experiment, this of course is guess- 

 work ; it only shows that a small number prove sufficient. 



In most Tsetse countries, the tras^eller is not usually beset with 

 more than two or three at a time ; in the course of the heat of the 

 day these might produce a number of bites, besides falling in with 

 fresh flies as one advanced. But they are sometimes found in much 

 greater numbers. On the 'south side of the Zambezi, near the 

 confluence of the Kafue, while walking along the river bank in 

 search of game, under shady flat-topped acacias, I heard a 

 buzzing sound, and saw a cloud of insects coming towards me. 

 Supposing them a swarm of bees, I ran ofi", while they followed. 

 On looking back I found it was only " Tsetse ;" so, arming myself 

 with a leafy branch, I kept them off" and continued my journey ; 

 they accompanied me for some distance however. I have never 

 again seen them congregate in this manner ; and, curiously enough, 

 on this occasion, and on this only, did I obtain two of what may 

 be the male insect ; these bear the proportion to the females of 

 1 : 30, judging by the numbers then caught. 



The systematic description of the "Tsetse" and its allies 

 having been minutely entered into by Professor "Westwood, I shall 

 only add a brief description of the parts composing the mouth or 

 biting apparatus. This consists of four pieces, of which two are 

 lateral setose palpi, for the protection of the proboscis and its 

 contained style. The lateral palpi are equal in length to the 

 horny proboscis, which they embrace when at rest, but are thrown 

 forward in a line with the body of the insect when in the act of 

 sucking. They are of a deep brown colour, almost black at the 

 tips, concave and finely hairy inside, outside convex and furnished 

 with dark setae, stronger and more numerous at the apex. 



What in the common fly is a soft fleshy proboscis, becomes in 

 the genus Glossina a straight, horny, chestnut-coloured bristle, 

 smooth and polished, the apex slightly dilated and rounded, the 



