390 



MOSQUITOES or NORTH AMERICA 



the house from below. About a large old house there are so many of these 

 chance breeding-places that only the most careful search will find them all. 

 Frequent change of water, or the use of kerosene, will render them all harmless. 



PREVENTION OF SEWER BREEDING. 



In community work in cities all of the points mentioned must be borne in 

 mind, and in the portions of the community where the residences are for the 

 most part detached villas, in the absence of swampy surroundings, the house- 

 holders are in the main responsible for the presence of mosquitoes. There are, 

 however, breeding places for which the town may be said to be responsible, and 

 these entirely aside from public fountains, reservoirs or marshes. It seems 

 unlikely that in any general sewerage system mosquitoes breed in the sewers 

 proper. That they do breed in the catch basins is well known. The purpose of 

 the catch-basin is to catch and retain, by sedimentation, sand and refuse which 

 would otherwise enter the sewer and obstruct it. It is intended to be water-tight 

 and to hold a considerable body of water which stands in it up to the level of 



Fig. 6. — Type of catch basin in common use in bacli yards 

 of Wasliington iiouses in wtiicli water stands permanently. 



the outlet pipe. Such catch basins are very commonly used in back yards and at 

 the crossings of streets. The water is replaced only by rain or when street or 

 yard surfaces are washed. In dry seasons the period of stagnation may last 

 several weeks, certainly long enough for mosquito breeding. As a matter of 

 fact, mosquitoes in midsummer do breed in such basin-traps or catch-basins. In 

 the work against mosquitoes in Brookline, Mass., in 1901 and 1902, previously 

 referred to, Culex pipiens was found breeding abundantly in catch-basins, and 

 more than 1000 such basins were regularly treated with petroleum. It is a 

 matter of common observation in the city of Washington that during the usually 

 dry months of July, August and September, mosquitoes are very numerous 

 throughout the city, in quarters where there are no possible breeding-places 

 other than these catch basins, and more particularly the large catch basins of 

 the sewer outlets at the street comers. 



The suggestion has been made that in cities it may, under certain circum- 

 stances, be possible for mosquitoes to breed in water accumulating in the under- 

 ground troughs of electric railways, but so far as known to the writers no exact 

 affirmative observations have been made. That there is abundant opportunity 

 for water to accumulate in these troughs and that it does so accumulate there 

 can be no doubt. 



