II 



they are numerous we may be sure that the vast majority 

 of them are being bred in the town itself in the gutters, 

 the ditches, the street puddles, the gardens and ponds 

 which lie amongst the houses. 



In searching for Anopheles larvce it is most necessary to 

 use a white bowl, or a white mug fastened to the end of a 

 stick ; because the larva are often almost invisible in clear 

 water with a dark coloured bottom. 



6. How to Find the Adults. During the day the 

 winged insects can be frequently observed sitting on the 

 walls, or under the roof, or in dark corners, and especially 

 in dark clothing, and inside hats hanging on pegs, and in 

 bathrooms, stables, and rooms occupied by natives. But 

 the reader must be warned that the number of insects 

 caught in houses during the day gives no accurate measure 

 of the number, especially of Anopheles, present during the 

 night. It is chiefly females gorged with a fresh meal of 

 blood which remain in the houses, the others generally 

 flying out in the early morning. Thus houses in which 

 scarcely a mosquito is visible during the day, may be 

 visited by large numbers at night This may often be 

 proved by persuading a native servant to sleep within a 

 mosquito net which has several small holes or rents in it. 

 Such a net acts as a mosquito-trap. During the night the 

 insects explore every part of the net in the hope of reach- 

 ing the inmate ; and many find their way in, but when 

 morning arrives cannot find their way out, and can then be 

 killed and counted.* 



* This mosquito-trap was suggested to me by Drs. ANNETT and BUTTON, 

 and was used with astonishing results by Dr. STRACHAN and myself at 

 Ibadan, Lagos, in a house where no mosquitoes could be seen in the daytime. 



