SIGNIFICANCE OF STEGOMYIA FASCIATA IN WEST AFRICA. 237 



and immediately around towns and villages on the banks o£ rivers and 

 streams, and along the seashore. These receptacles becoming filled by the 

 first shower of rain, and being to a great extent protected from the sun's 

 rays by the overhanging grass and leaves, the water does not evaporate and 

 ideal breeding places are thus afforded for the Stegomyia. To sum up, the 

 breeding places of the Stegomyia are almost exclusively artificial including 

 all receptacles in which, by accident or design^ water is stored, and not 

 repeatedly renewed. It is for this reason that all anti-mosquito by-laws 

 must be specifically directed against stagnant watei', which, in the tropics, has 

 been rightly termed ' the great enemy of mankind.' 



Stegomyia fasciata is usually regarded as a clean-water breeder, and so it is 

 for the most part ; occasionally, however, it will be found in very dirty water, 

 in company with the larvae of various species of Culex and Chironomus. I 

 have sometimes met with it in drains and marsh-pools in the vicinity of 

 houses. 



The striking feature about the Stegomyia, as Beauperthuy long ago 

 recognised, and one which every investigator soon appreciates^ is its 

 essentially domestic nature. It is the true ' house-haunting mosquito ' of the 

 tropics, and, like the cat and dog, is never far from the abode of man. I 

 have never seen them in swamps, far away from human habitations. 



These features in the life-history of the Stegomyia render it easily amenable 

 to control, or even extirpation. It is for that reason that it is very essential 

 in every town to make a precise survey to ascertain where the Stegomyia is 

 breeding. 



III. Stegomyia Surveys. 



To arrive at an accurate percentage in making a Stegoinyia survey, I adopt 

 either the house or the compound as the unit. In some countries it is very 

 easy to make the house and its yard the unit. In less advanced countries the 

 towns and villages are divided up into compounds or lots, and in each of 

 these there may be 2, 4, or 6 houses. Therefore, if the 'lot' or 'compound' 

 is taken as the unit, the number of houses in each should be recorded where 

 possible, but it is not always easy. 



In examining a house and its attached yard, the probability will be that the 

 larvae of the Stegomyia will be found in several receptacles. I make a record 

 of this in my note-book, as it bears upon the question of the total numbers of 

 the mosquito ; but for calculating the percentage I regard it simply as one 

 house in which the Stegomyia is present. In the case of a compound or yard 

 containing more than one house, if I find receptacles in that yard harbouring 

 larvce, I assume that all the houses are infected, as they are equally exposed 

 to the Stegomyia. 



The aim and object of the survey is to ascertain the number of houses in 



