32 MOSQUITOES 



in the closed sewers in Washing-ton, deserves more de- 

 tailed mention than we have given it. His house in 

 northeast AYashington being infested with mosquitoes 

 and no exposed standing water occurring in the vicinity, 

 he thought of covering* the small perforated sewer-trap 

 in his back yard with a wire screen. To prevent the pos- 

 sibility of mosquitoes entering- the screen from the out- 

 side, a layer of cotton Avas placed around the edge of the 

 trap on wdiicli the screen rested. On August 24th tAvo 

 females of Culex 2)^oige?is were found under the screen. 

 September 3d another was found in the same place, but 

 it went back to the sewer as soon as the rays of the sun 

 struck the screen. September 6th, 10th, and 11th, five 

 more were caught. Female mosquitoes in search of 

 breeding-places had evidently flown through the sewer- 

 trap perforations, had found standing- water in the sewer 

 and laid their eggs, from which a generation of adults 

 was develox3ed. 



There are other localities in Washington, far removed 

 from the Potomac Eiver front, where mosquitoes are more 

 or less abundant, and where there seems to be no standing 

 water in which they can breed. It therefore seems rea- 

 sonably sure that this sewer-breeding may be rather com- 

 mon in certain cities where the general slope is so slight 

 that the water may almost stand still for a few days, in 

 the absence of very heavy rains which flush the sewers. Of 

 course such breeding will easily be stopped by a little 

 neighborhood work, either by occasionally pouring a little 

 kerosene down the sewer-traps or by covering them with 

 a wire screen, as did Mr. Pergande in his experiments. 



