139 



are to be found constantly, though in small numbers, along routes 

 where during August and September they absolutely disappear, or are 

 present in almost negligible numbers, or only at odd times. This 

 applies to almost all the main routes, except just at and opposite the 

 four centres indicated. During late September, October and November 

 a distinct but gradual increase becomes evident, and during November, 

 before the rains, flies reappear in situations in which they were to be 

 found early in May. Radiations from the primary centres begin about 

 this period, so far as the physical character of the country, the large 

 garden clearings and the seasonal conditions allow. With the onset of 

 the rains the spread increases, as more suitable situations are created ; 

 the rough stony country becomes a habitat, and other breeding centres 

 4 secondary centres ' are established. The fly thus continues to 

 increase until the rains are over, the streams dry, and the grass 

 withered, and then the hot season with its bush-fires once more 

 performs a natural prophylactic measure. 



" On regarding the subject from this aspect, the measure which I 

 advocate is that the forest connections along which radiations take 

 place should be cut off, or otherwise dealt with, early in the year, 

 about May, so that the actual ' primary centres,' which should have been 

 delimited at the height of the previous dry season, are isolated. After 

 this has been performed all the trees in these centres should be cut 

 down and left to dry, and by the end of July or August, when the 

 whole country is parched (grass-fires having been strictly prohibited 

 during this period), wholesale and extensive burning should be carried 

 out over these areas, commencing from the side of the ' extensions ' and 

 progressing towards the main and isolated bodies of fly. At Kuti, 

 Nyansato and Patsanjoka (Rifu) this could be done, and with especial 

 ease at the last situation. At Lingadsi it would be difficult, but 

 sufficient could be done here to prevent a southern extension which 

 links up with the north arm of the Nyansato area during the rains. 



" If ' extensions ' depend on primary sources, as they undoubtedly 

 do, then it must needs follow that their limitation or the lessening of 

 their numbers must lessen the formation of ' secondary centres ' and 

 their ' extensions/ and will therefore curtail the distribution and 

 numbers of the fly. 



" Game plays a minor part in the actual habitat of G. morsitans. It 

 is true that in the above-mentioned areas game is plentiful and that 

 blood is necessary to the life of the fly, but there are numerous situations 

 where game is present in this same prohibited area, yet fly are not 

 found, and where fly though present during the wet season are absent 

 during the dry." 



Unfortunately subsequent investigations by Dr. W. A. Lamborn, in 

 the same " sleeping sickness area " as that studied by Dr. Shircore, 

 do not appear to confirm the methods of clearing advocated by the 

 latter. 



" Though the fly," writes Dr. Lamborn (82), " does occupy certain 

 definite regions in the dry season from which, as I quite agree, they 

 radiate out farther afield when the grass springs up everywhere and 

 the game spreads abroad, the foci, in this district at all events, are in 

 my opinion far too extensive to make any experimental attempt at 

 clearing and reducing their number by systematic capture practicable. 

 I have not been able to discover that the ' primary centres ' form 

 localised breeding grounds, so that this very attractive hypothesis is 

 up to the present unsupported by a shred of evidence." 



