288 ILLINOIS STATE ACADEMY OF SCIENCE 



ing place. Drainage of swamps, marshes and ponds can 

 be effected by the construction of open ditches or tile 

 drains, preferably the latter because of their perman- 

 ency. In some cases ponds can be drained by vertical 

 drainage. Old ditches with numerous potholes should 

 be regracled and cleared in Order to drain the potholes 

 and keep the grass and weeds away from the water. A 

 small trench cut in the bed of an old ditch or stream will 

 confine the dry-weather flow and do much to keep the 

 grass and vegetation from encroaching. A tile laid in 

 the bed of an old ditch will remove the trouble entirely. 

 Small depressions and pools can sometimes be more eco- 

 nomically filled than drained. 



The work of clearing as an antimosquito measure can 

 not be over-emphasized. The "work appears of little con- 

 sequence perhaps, yet in many instances at least 90 per 

 cent of the breeding can be destroyed by this work alone. 

 If stagnation of the water is prevented and the marginal 

 vegetation removed, there can be but little breeding. 



Places that can not be drained or filled in should be 

 treated in some manner. Oil is the most efficient as well 

 as the cheapest larvicide known at the present time. In 

 some cases lime, hog dip, niter cake, and other com- 

 pounds can be used to good advantage. The oil, in addi- 

 tion to creating a thin film over the water surface 

 through which the wiggler can not penetrate its breath- 

 ing tube, acts as a poison and kills the wiggler much 

 more quickly than by suffocation. Kerosene is effective 

 and easily spread, but evaporates comparatively rapidly. 

 Kerosene mixed in the proportion of about 4 to 1 with 

 crude oil makes the best mixture. The oil may be ap- 

 plied by sprinkling oil-soaked sawdust along the edges 

 of lakes or streams, by oil drips, swabs, or sprayers. The 

 sprayer is considered the most effective implement, the 

 Panama knapsack sprayer being the one more widely 

 recommended. Because the oil evaporates or after a 

 while separates so as not to form a continuous film over 

 the surface of the water, oiling must be done at regular 

 intervals of about 7 days. 



Paris green is strictly a malarial mosquito larvicide. 

 When mixed in the proportions of about 2 parts Paris 



