258 TROPICAL MEDICINE AND HYGIENE 



should be made twice a week, and any foul drains, or 

 cesspits should be treated with crude petroleum, or 

 better, some such poison as tuba root (Derris elliptica). 



With a good organization, with the active support of 

 the intelligent section of the community, and stringent 

 regulations well enforced, the cost of extirpation of this 

 mosquito is not prohibitive. 



Roof water forms the best available supply of drinking 

 water in many places, so that measures that prevent its 

 infection cannot be overlooked. 



Dengue fever is conveyed mainly by Culex fatigans and 

 Stegomyia fasciata, but it also occurs in places where the 

 latter mosquito is not found. Stegomyia scutellaris, easily 

 distinguished by the broad median white band down the 

 thorax, is also a carrier. S. scutellaris also breeds in foul 

 water, and is common in similar conditions to those in 

 which S. fasciata is found, but occurs in jungle, and more 

 on the outskirts of settlements than in the larger crowded 

 townships. 



Culex fatigans, which, as well as the Stegomyia, is impli- 

 cated in the conveyance of dengue fever and is the 

 common carrier and intermediate host of Filaria ban- 

 crojti, breeds in roadside ditches and in almost any 

 collection of still water. It is a domestic mosquito and 

 is found in houses, often in large numbers, but, unlike 

 Stegomyia fasciata, the breeding-places are often a long 

 way from the houses it frequents as an imago. The ex- 

 tirpation of C. fatigans from a settlement requires com- 

 bined effort, practically municipal control, whilst the 

 freedom of a house from Stegomyia mainly depends on 

 the individual care of the occupant of a house. Houses 

 on the top of a hill are often much frequented by 

 C. fatigans ; these mosquitoes are strong fliers and are often 

 carried, partly by the wind, for considerable distances, 

 they seek shelter in the houses and will remain in such 

 houses resting and quiescent in the day time, but active at 

 night. Under artificial conditions they may live for three 

 months or more, and under natural conditions will hiber- 

 nate all through the cold season. 



