328 W. B. JOHNSON. 



as the common mosquito larvae obtained may not be the common domestic mosquitos. 

 At Zungeru I have bred out large numbers of mosquitos, and would have come 

 to the conclusion from that alone that Stegomyia vittata (sugens), Uranotaenia^ 

 Icoeruleocejjhala and Culiciomyia nebulosa were the common mosquitos of the 

 station, whereas only the latter was obtained in my house, and that only rarely. 

 Next in order of frequency I bred out A. costalis, A. funestus, Culex decens, C. invi- 

 diosus and C. ager. The list given below shows (1) mosquitos obtained from larvae 

 at Kaduna, Zungeru, and Katagum, but not caught as adults in my house, and 

 (2) adult mosquitos caught in these stations but not in houses : — 



-r, , , . , , , . , Caught as adults in station, 



Bred from larvae, not caught m house. * but not in houge _ 



Stegomyia vittata 



,, unilineata 

 Ochlerotatus Iwellrnani 



Stegomyia vittata 



,, apicoargentea 

 „ africana* 



„ tquasiunivittatus 

 „ Ipunctothoracis 



„ svmpsoni* 

 Ochlerotatus cumminsi* 



Taeniorhynchus annetii 

 Uranotaenia Icoeruleocephala 



Culex annulioris 



* Caught by the late Dr. J. E. L. Johnston in 1914 at Radius 



7. Conclusion. 



(a) The common mosquitos which infest houses in certain stations in Nigeria, 

 N.P., are Anopheles costalis, Theo., A. funestus, Giles, A. rufipes, Gough, Culex 

 decens, Theo., and C. invidiosus, Theo. These five species together formed 97 -1 per 

 cent, of 11,514 mosquitos caught in the medical officer's house at Kaduna, Katagum, 

 and Zungeru, during a period of 89 weeks, whereas the remaining 17 species obtained 

 formed only 2*9 per cent, of the total. It is tempting to state that for purposes 

 of parasitological work these five species alone need be considered, but there is an 

 obvious fallacy in such a statement in that certain other species are really common, 

 but are kept under control by anti-mosquito measures, to which they are especially 

 vulnerable owing to their selection of breeding places. Amongst this latter class 

 must be placed Stegomyia fasciata, F., Culex duttoni, Theo., and Culiciomyia nebulosa, 

 Theo. It should also be remembered that in certain stations Mansonioides 

 uniformis, Theo., is numerous and may also be a house-infesting mosquito. 



(b) Other species of mosquitos may be breeding freely in a station but may not 

 be domestic pests — e.g., Stegomyia vittata, Big., S. unilineata, Theo., Uranotaenia 

 %coeruleocepliala, Theo. 



(c) The seasonal variation of mosquitos as domestic pests, which is well shown 

 in the graph (fig. 1), is, I think, typical of what occurs generally in stations in 

 Nigeria, N.P. This may be usefully remembered in comparing seasonal sickness 

 returns for this country, especially returns of " pyrexia of uncertain origin." 



In conclusion I wish to express my deep obligation to Col. A. Alcock, F.R.S., 

 Mr. F. W. Edwards, and Dr. and Mrs. Connal, of the Medical Research Institute, 

 Yaba, for kindly confirming my identification of species from time to time. 



