236 SIR RUBBRT BOYCE — THE PREVALENCE, DISTRIBUTION AND 



liable to contain larvae. In Louisiana, Central and South America, the large 

 wooden rain-water vats are the common offenders. In many o£ the West 

 Indies large stoneware jars (olive jars) create a nuisance. In Trinidad the 

 " antiformicas '' placed around flower-beds to protect the flowers from the 

 attacks of the umbrella ant, usually harbour larvae. In Freetown the habit 

 of making 'ornamental' borders to flower-beds by sinking into the earth 

 a row of inverted bottles is a fertile source of Stegomyia ; the cup-shaped 

 depression at the bottom of the bottles holds water, and in these tlie 

 Stegomyia deposits her eggs. Imperfectly broken glass on walls is another 

 source. Eot-boles of all kinds in trees, the axils of the Aroidese, of the 

 Traveller's Palm, and of many other plants, form receptacles which ma}^ 

 prove a nuisance. I have found larvae breeding in the puddles formed on 

 the flat mud roofs of houses in Cape Coast Castle. The roof-giitters of 

 houses are common receptacles. Less frequent breeding places are marsh - 

 holes, puddles and drains. I have found Stegomyia larvae in all these latter 

 places, but, in my opinion, less frequently. In my experience, this mosquito 

 most frequently selects, for breeding purposes, wooden receptacles of all 

 kinds, especially barrels in which there is a thin coating of minute green 

 algae ; next in frequency, all small collections of water in tins and cans of 

 every description, when protected by the shade of foliage from the sun's rays 

 and the heavy rains. In West Africa I have not met with epiphytes growing 

 in any abundance upon the trees, indeed the Bromeliaceae are conspicuous by 

 their absence. In the West Indies the reverse is the case. When they are 

 present they collectively hold a large quantity of water and support a very 

 large number of larvae. 



As the investigator gains experience two facts begin to strike him. 

 Firstly, the very small quantity of water, from a teaspoonful upwards, which 

 will suffice as a breeding place for the Stegomyia ; and on this account, the 

 smallest odds and ends which may contain water should be examined. 

 Secondly, the immense number of discarded empty sardine tins, milk tins, 

 meat tins and tin cases of all kinds which are to be found in all towns 

 opening up to commerce. A veritable tin can invasion extends up from the 

 coast towns into the interior villages. The more traders, the more tin cans ; 

 the nearer the more primitive villages are approached, the less become the 

 white traders and the less, in consequence, the number of discarded tins. In 

 other words, tinned foods of all kinds, oil tins and tin packing cases are most 

 abundant where there are white settlers and traders. This has brought about 

 a condition which immensely favours the development of the Stegomyia. 

 The total water-holding capacity of these discarded tins is very great indeed, 

 vastly greater than the inexperienced would at first sight suppose. For the 

 tins are not always obvious when you enter a compound ; the fact being that 

 the larger number are concealed amongst the weeds and low bush which 

 invariably is present in the majority of compounds, and on waste places in 



