XVl] BIONOMICS 289 



37° C. and a minimum of 10° to 12° C, and an average humidity 

 of 66 to 8^ %. In British East Africa it occurs at varying 

 levels from the sea coast to Fort Hall, a height of 4000 feet. 

 According to Dr P. H. Ross, in the valley of Kibwezi it is generally 

 found among rocks on the hills, resting on the slightly damp 

 black cotton soil between boulders. It may be caught in 

 quantities all the year round, but is more abundant during the 

 wet season. It is said to be markedly nocturnal in its feeding 

 habits and on one occasion was met with in numbers resembling 

 a swarm of bees. On the other hand Milne states that the fly 

 generally bites between three and five in the afternoon, and in 

 the Kibwezi valley is more prevalent during May and June 

 than any other time of the year. 



In German East Africa, Stuhlmann found that the fly was 

 present at Anami all the year round, but Keysselitz and Mayer 

 state that very few females could be captured during December, 

 January and February. Like many other species of tsetse-fly, 

 G. hrevipalpis occasionally follows animals to some distance 

 from its actual haunts and Stuhlmann notes that in this way, 

 especially during the hot weather, isolated examples were 

 frequently found amongst the mountains at altitudes up to 

 3250 feet, whilst during December to April the flies were often 

 met with in the settlements. 



In Nyasaland, Davey recorded the capture of a few indi- 

 viduals belonging to this species, all of which, with one exception, 

 were caught within 900 yards of the edge of Lake Nyasa. 

 Sanderson was informed by the natives that during the rains 

 (January) , at which time practically the whole country is under 

 water, G. hrevipalpis is very prevalent in North Nyasaland all 

 over the grassy plain lying between the shore pf the lake and a 

 line of foot-hills some ten miles away. In June and July this 

 species was found, sometimes in very large numbers, in the 

 beds of all the streams between Karongo and Sougive, although 

 many of them were dry. It was occasionally caught in the 

 native villages. 



According to Dr Sanderson, G. hrevipalpis is active and 

 desirous of feeding only in the early morning before 8.0 o'clock 

 and in the evening after about 4.0 o'clock. During the day- 



H. B.F. 19 



