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DOMESTIC MOSQUITOS OF THE NORTHERN PROVINCES OF NIGERIA. 

 By W. B. Johnson, M.B., B.S., F.R.C.S., 



West African Medical Staff. 



During six years medical work in the northern provinces of Nigeria I have caught 

 and examined every morning all the mosquitos I could find in my own bungalow. 

 I have done this with a view to finding out which are the common domestic species 

 in this region of West Africa, and their seasonal variation throughout the year. 



The results are shown in the first four tables appended, and Table V shows a 

 combination of the totals of all these tables. 



The work has been done at Kaduna Junction (1917-1918), Katagum (1916), 

 Zungeru (1915-1916), and Zungeru (1912) ; and the four series of figures show 

 marked similarity. Kaduna Junction is placed on the left bank of the Kaduna 

 River in Zaria Province. It is on laterite, hilly ground sloping towards the river, 

 which forms a half circle round the station. An extensive marsh in the rains lies 

 to the east of the station, and partly flooded marshy ground lies along the river 

 banks at high water. A series of thickly-wooded gullies traverse part of the station 

 towards the river, and afford additional mosquito breeding-grounds. Katagum 

 is a small bush station on sandy soil on the left bank of the Katagum river in Kana 

 Province. In the dry season the river ceases to flow, and remains as a series of 

 pools in the sandy river bed, but in the rains it floods the surrounding country, 

 and the station is merely an island surrounded on all sides by marsh. Zungeru 

 is placed in the angle of junction of the river Dago with the river Kaduna in Niger 

 Province. It is built on three laterite ridges, between two of which flows the Dago 

 River ; between the other two ridges is marshy ground during the rains, and 

 rocky pools and marsh lie along the banks of both rivers, except during very high 

 water. 



Before commenting upon the figures given in the tables it must be pointed out 

 that inexpensive anti-mosquito measures are energetically carried out in the stations 

 referred to. Thus water-tanks when present are screened, gutters pierced, and 

 compounds visited frequently by the medical officer ; the occupant of any com- 

 pound is fined if larvae are found. These measures diminish enormously the 

 numbers of such domestic-breeding mosquitos as Stegomyia fasciata and Culex 

 duttoni, which occur in great numbers if the work is neglected. Grass and bush 

 is cleared by prison labour or by labour paid out of the sanitary vote ; but extensive 

 anti-mosquito measures, such as drainage of swamps, are not possible owing to lack 

 of funds for the purpose. 



During the periods recorded, which extended over 40 +7 +27 +15 = 89 weeks, 

 I have caught in my own bungalow 11,514 mosquitos. Referring to Tables I- VI, 

 the following points appear worthy of notice : — 



