51 



and French Sudanese zones, though identical in appearance with those 

 in which G. morsitans occurs, are totally wanting in this species of 



Tsetse Now, the only differences that seem to us to explain 



this absence of the fly consist in the fact that game is more or less 

 scarce. G. morsitans always swarms in French West Africa in very 

 scantily populated regions, where human activity is of little intensity, 

 while the soil is scored by the spoor of wild animals, testifying to their 

 incessant movements to and fro in complete freedom from all restriction. 

 In these regions, again, man is bitten but occasionally by this fly, 

 when he ventures into the infested zones. G, morsitans is never met 

 with as G. palpalis is encountered, in small foci at a distance from the 

 main zones, and in proximity to man alone." 



" Generally speaking, G. morsitans zones are met with much further 

 to the north than those infested by G. longipalpis, as was only to be 

 expected in view of what has already been stated as to the fondness 

 for dry places exhibited by the former species. In French West 

 Africa there are at least four great morsitans zones, in all probability 

 continuous one with another at least during a portion of the year, and 

 lying between 10 and 14-5N. Lat., from Nigeria to Senegal. Of 

 these zones the most important is that which comprises the hinterland 

 of Guinea, Upper Casamance, Upper Gambia and the corresponding 

 regions of Thies-Kayes. I have already pointed out elsewhere (121) 

 that, as the furthest outpost towards the west, this zone still exhibits 

 in the fly-belts of the Niom-Bato a proof of its former continuous 

 extent. 



" It is, moreover, probable that, as regards their geographical limits 

 at the present time, these morsitans zones are not absolutely fixed ; 

 indeed, among the principal factors producing corresponding variations 

 in the morsitans fly-belts we must include the migrations of game and 

 the possible variations in the abundance and size of the herds of wild 

 animals. 



" All causes capable of producing variation in the distribution of 

 big game hunting forays, epidemics, railway extensions, etc. will 

 necessarily also have a repercussion on the dispersion of G. morsitans, 

 which, in view of this, must be considered much less stable than that 

 of the other Tsetse-flies." 



Instructive statements as to the habitat of G. morsitans in the North 

 Mossurise district, Portuguese East Africa, are given by Mr. C. F. M. 

 Swynnerton (145), as the result of three months' personal observation, 

 from June to September 1918. After describing the haunts of G. 

 brevipalpis, the author in question continues:" Glossina morsitans 

 was found in a very different kind of country. It was very obviously 

 far less dependent on good shade than G. brevipalpis, and I failed to 



iind even stray individuals in the densest forest types It 



occurs both on the granite-gneiss and the basalt of the lowlands, the 

 latter usually with very poor bush indeed ( Combretum, etc. . .), 



and the former with savannah forest of a poorer type than that of the 

 sedimentary area, though in each of these two it is a Brachystegia. 

 On the basalt and on most of the gneiss this fly occurred during my 

 visits only as very rare individuals, and on the basalt and away from 

 vleis only males were taken. The granite-gneiss, however, carries 



very numerous vleis, many of them with permanent 



water, and in spite of much painstaking search elsewhere, it was only 

 at these vleis (and then only at some of them) that morsitans was found 



