INSECTS AND DISEAS£ 
Watch, then, for unused barrels, tubs, and buckets; roadside 
puddles; hoof prints, ruts, and depressions of all sorts; barn-yard 
pools; and the like. In cities, special attention must be paid to the 
catch basins of street sewers which are often prolific breeding places. 
In attempting to locate wrigglers in such places water should be 
skimmed (not scooped) from the margins of the water in a white- 
lined cup or dipper. Fountain-basins should contain goldfish since 
these fish are voracious feeders on mosquito eggs and larve, or the 
basins should be emptied and thoroughly dried at least once a week 

Fig. 19. OILING A MOSQUITO-BREEDING SWAMP 
during the mosquito season. If for any reason a pool or pond cannot 
be drained there are two principal methods of preventing it from 
furnishing the neighborhood with mosquitoes: the surface may be 
covered once a week with a film of oil; or surface-vegetation may 
be removed, the sides of the pool made sharp and steep, and the 
pool well stocked with goldfish. The first method is not entirely 
satisfactory since the oil must be renewed so often, and also because 
an oiled pool has an unpleasant look and odor. Kerosene spreads 
well but evaporates quickly: crude oil lasts longer but does not 
41 
