23S SIR HUBERT BOYCE — THE PREVALENCE, DISTRIBUTION AND 



u town or village in which, or immediately around which, Stegomyia are 

 breeding, and which, therefore, are infested with the mosquito. I have 

 worked out these percentages for a great number 'of the larger towns in the 

 West Indies and British Guiana, and also in British Honduras, and I am of 

 opinion that they give a very fair idea of the distribution of the Stegomyia. 



The size of the vessel in which the larvae are found only affects the 

 question of the total number of the insects. The presence of only two larv?e 

 in a teaspoonful of water, contained perhaps in a snail shell or the broken 

 end of a bottle fastened into a wall, is not less significant than the presence 

 of hundreds of larva3 in a barrel ; for it shows how ubiquitous that particular 

 mosquito must be. 



lY. Some characteristics of the Stegoiitia and its Larv^. 



Having now had several years' experience of this mosquito, I record here 

 those features which appear to me to be most characteristic. The most 

 salient point is the essentially domestic instinct of this mosquito, which is, 

 above all others, the most 'house-haunting' species. I have never found it 

 breeding far from the abode of man, not more than^ say, 50 to 100 yards *. 

 It is fond of dark situations, breeding preferably in shaded barrels and odd- 

 and-end receptacles. Therefore a most favourite site is any water vessel, 

 such as a jar or barrel, stowed away in a corner in the kitchen^ or in a 

 bedroom. 



The mosquito avoids windy places, and therefore selects not only quiet 

 stagnant water, but places where the air is stagnant. As soon as the imago 

 emerges from the pupa, it makes for the dark places in the house. It alights 

 preferably on dark or black material. So far as I have been able to judge, I 

 do not think that it flies any great distance at one time, although of course 

 its travelling may be very greatly assisted by the cover of trees or a long line 

 of huts, wdiich would enable it to progress horn point to point, sheltered from 

 wind and rain. Some observers give 100 yards as its maximum distance of 

 flight. Whatever this may be, however, I consider that it may safely be said 

 that this mosquito does not, as a rule, fly long distances. It seeks cover as 

 soon as it emerges from the pupa, but it may travel from house to house, and 

 is certainly capable of entering ships moored in rivers. In conformity with 

 itr^ house-haunting domestic nature is the fact that it is probably the most 

 connnon mosquito found on ships ; numerous observations in recent years, 

 and the endless records of yellow fever on board-ship in the nineteenth 

 century, amply testify to this fact. Given the suitable conditions of 

 freedom from draughts, darkness and warmth^ it can remain secreted for 



* ]5ouffard places the distance limit at 100 moires ; Le Moal gives it as 250 metres. 



