CONDITIONS IN EAST AFRICA. 13 



scarcity of game " even along the banks of the river.'' He 

 adds : "Here are great stretches of uninhabited bush country 

 with a perennial river running through it, and hardly any 

 animals, though plenty of birds and of ' fly ' (Tsetse)." More 

 recently, in a letter to the Marquis of Lansdowne, dated 27th 

 September, 1901 (see Chapter VII., Appendix C, p. 297), Mr. 

 Jackson has expressed the belief that "the Tsetse is, like the 

 mosquito, only a blood-sucker by predilection." The meaning of 

 this phrase would appear to be that, in default of blood, which 

 it prefers, the Tsetse can continue to subsist on the juices of 

 plants. Be this as it may, it must, I think, be regarded as an 

 established fact that when game absolutely ceases to exist in a 

 given locality, the Tsetse-fly, if present, soon disappears. As an 

 argument in support of his belief, Mr. Jackson mentions that 

 near Kibwezi, in East Africa, in April 1892, " at a time when 

 the whole of the ' fly-belt ' was parched and dried up — there 

 being no water between Msogoleni and Tsavo River, a distance 

 of fifty miles, and consequently no game of any kind — the Tsetse 

 was more plentiful than at any other time, before or since," 

 when he has traversed that district. He also states that though 

 a species of Tsetse is " plentiful " in the Botanical Gardens at 

 Entebbe, on Lake Victoria, there are no mammals there " with 

 the exception of a few monkeys and squirrels, and certain small 

 nocturnal beasts, such as ichneumons, etc., and an occasional 

 hippopotamus." Whether the proboscis of the Tsetse can pierce 

 the integument of plants as easily as that of mammals has yet to 

 be proved by actual observation ; at any rate no one has so far 

 ventured to make such an assertion. But in connection with 

 Mr. Jackson's statements it must be remarked that even 

 assuming that the Tsetse in the Botanical Gardens at Entebbe 

 make up for the deficiency in the supply of mammalian blood 

 by imbibing the juices of flowers and plants, those in the fly- 

 belt near Kibwezi could hardly have done so, since we are 

 expressly told that at the time referred to the whole area was 

 " parched and dried up." 



The true explanation of the Kibwezi phenomenon seems to 

 be that it is possible for one generation of adult Tsetse-flies, as 

 for other adult insects, to continue to live for some time or for 

 the whole period of existence without food, if the latter is not 

 forthcoming. Thus assuming a fly-belt to be deprived of all 

 mammalian life, the Tsetse-flies which thereafter emerged from 

 pupae would continue to exist even though fasting ; and they 



