i^4 Mosquitoes 



taste to water in cisterns or barrels, unless the film is 

 very thin. The cost is thirteen cents per gallon or 

 less; an ounce, sprayed on, covers fifteen square 

 feet, and it kills not only larvae and pupae but catches 

 the adults; it is, therefore, by virtue of its simplicity, 

 cheapness, and efficiency, the best larvicide for many 

 purposes, where the odour is not offensive nor dis- 

 infection desirable. The effectiveness of a film of 

 kerosene will last one or two weeks with no rain, 

 according to temperature and amount of shade. 

 Calculating on the average growth of a larva, oiling 

 with fuel oil once in fifteen to twenty days will be 

 absolutely safe. Crude petroleum, having a ten- 

 dency to form masses rather than films, is not as 

 satisfactory. 



The "Bordeaux Mixture" of lime and copper 

 sulphate, and the last in simple solution have 

 popularly been supposed to be good larvicides ; but 

 Mr. Dickerson's experiments prove them to be unre- 

 liable as such. As, however, they kill out the algae 

 and microscopic forms in a pool, thus destroying 

 hiding places and food of the larvae, there is undoubt- 

 edly a great diminution of larvae on that account. It 

 might be worth trying;, where there are no fish, but 

 as copper sulphate is fatal to many of the finny tribe 

 and harmless to most larvae, its use in fish ponds is 

 net to be recommended. 



While salt prevents many mosquitoes from ovi- 

 positing, yet it does not, in many cases, kill larvae 

 already in the water, but simply hastens maturity. It 

 does kill the newly hatched larvae of some species, 

 and it is my impression that Stcgomyia is one of these, 



