DESTROYING AXD REPELLING MOSQUITOES 93 



kill the larger part of larvae and pupa? in such pools. A 

 similar experiment repeated in another ditch gave pre- 

 cisely similar results with one additional point worthy 

 of note. In one of the pools carefully observed, a thin 

 mass of Algae and scum rested over quite an area adja- 

 cent to one of the banks. In it were many larvae and 

 pupae. Into this mass the oil never penetrated, and in 

 my opinion with that current never would, no matter 

 how many applications were made. 



It would seem then, that the only sure and quick remedy 

 for such places is to spray the oil on the surface. By 

 this method many adults are killed at the same time. 

 If poured into the sewer, several successive applications 

 must be made to be in any degree effective, and even then 

 in pools where there was algal slime it would have little 

 effect. It is evident, that if the sewer pipes empty into 

 pools or bodies of water with no current, the above con- 

 clusions would not apply. 



FUMIGATING ROOMS TO KILL MOSQUITOES 



It is often desired to free a house entirely of these 

 insects. The best and most effective way to do this is 

 to fumigate the rooms with some substance which will 

 either stupefy or kill them. Many substances are used 

 by campers and hunters to drive insects away, but for 

 fumigating houses quite different materials are used. 

 Probably sulfur is most universally used, while pyre- 

 thrum, culicide, and a few other substances are occasionally 

 tried. 



Pyrethrum. — Pyrethrum was originally produced in 

 Asiatic countries only. Now the plant from which it is 



