is not ensheathed in the palpi, and is consequently much more slender 

 in appearance than the proboscis of Glossina. The species of the 

 former genus are usually greyish, greyish-black, or blackish flies, and 

 since their wings, when in the resting position, instead of closing one 

 over the other, diverge at an angle (see Fig. 2), like those of Musca 

 domestica, it is easy to distinguish them from Tsetse-flies. Haematopota, 

 on the other hand, a genus of small horse-flies (Family Tabanidae) 

 abundantly represented in Tropical Africa, resembles Glossina some- 

 what closely when at rest. Although the species of this genus are 

 of much the same elongate shape as Tsetse-flies, their wings in the 

 resting position do not close one over the other, but diverge slightly 

 at the tips and are also somewhat tectiform, i.e., they meet together 

 at the base like the roof of a house (Fig. 3). The antennae, too, 

 afford a t further means of distinction. While the antennae of Tsetse- 

 flies, as 'of all other Muscidae, are drooping, those of Haematopota 

 project horizontally in front of the head, and being of some length are 

 readily seen " (Austen). 



Geographical Distribution of Tsetse- Flies in General. 



" Although, since the discovery of Glossina tachinoides, Westw., in 

 Southern Arabia, the generalisation that existing Tsetse-flies are con- 

 fined to Africa no longer holds good, it is nevertheless true that the 

 genus Glossina at the present day occurs only in the Ethiopian region, 1 

 inasmuch as the southern portion of Arabia, belongs zoo-geographically 

 to the region in question. In the African continent Tsetse-flies have 

 a very wide distribution in the tropical and sub-tropical zones. Roughly 

 speaking, so far as our present knowledge goes, the northern boundary 

 of the genus may be represented by a line drawn from the mouth of 

 the Senegal River across the middle of Lake Chad to the Nile, just 

 south of the twelfth parallel of north latitude, and thence to the east 

 coast at about 4 N. ; while its southern limit may similarly be shown 

 by tracing a line from the mouth of the Cunene River, the southern 

 boundary of Angola, to the north-eastern extremity of St. Lucia Lake, 

 in Zululand. Within this area Tsetse-flies .... are not found 

 continuously, but are restricted to ' belts ' or ' patches ' of forest, 



1 There is, however, scientific proof that, at a remote epoch, Tsetse-flies also 

 existed in North America, for within the last thirty years the fossil remains 

 of no fewer than four species of Glossina have been found in the Miocene shales 

 of Colorado. Professor T. D. A. Cockerell (31), to whom our knowledge of 

 these species is chiefly due, has drawn attention to the interesting theory 

 originally advanced by Professor H. F. Osborn that the disappearance of many 

 large mammals from America may have been directly connected with the former 

 presence of Tsetse-flies in that continent. 



Nowadays, with the exception already mentioned, outside the African 

 continent Tsetse-flies are found only in two islands in the Gulf of Guinea 

 Fernando P6 and Principe, both of which are, or were until recently, infested 

 with G. palpalis. The occurrence of the fly in the former may well be the result 

 of natural immigration, since this island is only 25 miles from the African coast, 

 In the case of Principe, which is separated from the nearest point on the main- 

 land by a distance of 125 miles, according to Da Costa and his colleagues (41) the 

 insect is said to have been imported at the beginning of the nineteenth century, 

 " at a time when the slave trade and the cattle trade kept alive a frequent 

 movement of shipping between the island and different points on the coast of 

 the Gulf of Guinea, especially the Gaboon." The remarkably successful measures 

 fay means of which this island has practically been freed from the scourge 

 are referred to below (pp. 142-143). 



