250 INFECTION AND IMMUNITY 



stagnant water, whether large or small, and destroys 

 the larvae, which are obliged to come to the surface 

 from time to time for air. An ounce of oil is said to 

 be sufficient for fifteen square feet of surface, and an 

 application of this amount to be effective for about 

 two weeks. 



The destruction of adult mosquitoes near dwellings 

 may be to some extent accomplished by placing lighted 

 lamps, in plates containing petroleum, at a little dis- 

 tance from the house. The mosquitoes fly about the 

 lamps and many of them are likely to fall into the 

 petroleum, which quickly kills them. The task of kill- 

 ing mosquitoes inside of a house is, however, far eas- 

 ier than that of destroying those on the outside. Their 

 entrance should as far as possible be prevented by 

 the use of window and door screens. Those which 

 pass these barriers should be destroyed by burning, 

 in the closed apartments, pyrethrum powder, or by 

 fumigation with formaldehyd gas or sulphur dioxid 

 (formed by burning sulphur). It is especially import- 

 ant that all mosquitoes should be killed in the 

 autumn in houses located in malarious regions. 

 Otherwise they are likely to hibernate and the females 

 will serve in the spring to start a new generation of 

 annoying and possibly dangerous pests. They are to 

 be found not only in bedrooms, but in cellars, kitch- 

 ens, closets, and attics. 



