﻿RESEARCH IN BRITISH WEST AFRICA. 191 



Only two species belonging to the morsitans-gvouip occur in this area, namely, 

 G. submorsitans and G, longipalpis. The former is confined entirely to Northern 

 Nigeria, while the latter, though fairly abundant in Southern Nigeria, is very scarce 

 in Northern Nigeria and is found only in the southern portion. Neither of these 

 species is so intimately associated with the rivers as G. palpalis, but they are 

 found in the more open country. Broadly speaking, G. submorsitans inhabits 

 the drier regions where the savannah forest is predominant, being, consequently, 

 similar in habits to G. tachinoides ; while G. longipalpis is associated with a moister 

 climate and a slightly denser vegetation of the mixed deciduous forest type. 



The distribution of G. fusca is almost coterminous with that of G. longipalpis 

 and its habitats are similar. It favours dense vegetation and a moderately 

 moist climate. 



I hope in a future paper to deal at greater length with the distribution of not 

 only Glossina* but also the various species of Tabanidae and Cueicidae, but 

 these few notes may serve to show along what lines the factors influencing 

 distribution may be sought. 



One thing at least is evident from a study of the distribution of the various 

 species of Glossina, namely, that cattle and horse trypanosomiasis in Nigeria is 

 not associated with one and only one species. This disease is prevalent in the 

 Lake Chad area, where only tachinoides and submorsitans are found, while it is 

 equally prevalent in the western province of Southern Nigeria, where palpalis 

 and longipalpis are the predominant species. 



In my report on the Gambia* I added a few notes on the bionomics of Glossina, 

 and as these are equally applicable to Southern Nigeria, there is little necessity 

 for again recording them. Further, throughout the present report I have added 

 whatever seemed important as to prevalence, nature of habitat, &c, of Glossina 

 palpalis, but I should like to draw attention to our scanty knowledge of the 

 bionomics and life-histories of the other and rarer species. 



VII. — The Distribution of Stegomyia. 



In view of the connection between this genus of mosquitos and yellow fever, 

 it has been considered advisable to recall briefly what is known as to its prevalence 

 in Southern Nigeria. Two papers have recently appeared in this Bulletin 

 bearing upon this question, so that I do not propose to deal with it at any length. 

 The first of these papers was by the late Sir Hubert Boyce,f in which he drew 

 attention to the prevalence of yellow fever in West Africa and afterwards to the 

 high percentage of Stegomyia fasciata mosquitos in the coast towns. The second 

 was written by Dr. W. M. Graham, J and gave the results obtained from a 

 monthly examination of native domestic water-receptacles at Lagos in 1910-11. 

 The total number of receptacles examined was 1,043 and in 965 of these, i.e., 

 92*5 per cent., larvae of Stegomyia fasciata were obtained. He proceeds to say : 

 " It is the commonest species of larva, is widely distributed over the township 



* Bull. Ent. Res. II, pt. 3, pp. 187-239. 

 f Bull. Ent. Res. I, pt. 4, pp. 233-263. 

 % Bull. Ent. Res. II, pt. 2, pp. 127-136. 



