58 DRAGON FLIES VS. MOSQUITOES. 



and reiidily applied, petroleum in its various prescribed 



dilutions may be given a very important place in this 



list. Its many qualities commended themselves to us 



early in our search after the possibilities, and the great 



measure of success met will be discussed further on. 



Petroleum compounds have had favorable mention from 



several writers in our bibliography — notably, Cornelius,^^ 

 Riley,^26,i27andMiot.93 



Leaving the inorganic insecticides, we come to a class 

 of vegetable poisons belonging to the fungoids. Here we 

 find at once a most difficult, yet promising field ; one that 

 seems to us to be a more promising one than any yet ex- 

 plored. As an introduction to this subject we may men- 

 tion that classic of scientific research by Pasteur ^^^ on the 

 diseases of the silk worm. So suggestive is this work, so 

 full of food for thought, that it is surprising to note how 

 very little has really been accomplished in the study of 

 these insecticides. 



The Entomophthorfe, fungoid growths upon insects, 

 are undoubtedly a potential class of insecticides, with 

 great recuperative and reproductive capacities, and are 

 seemingly so organized as only to need a thorough in- 

 troduction into a colony to enable them to carry on their 

 death dealing mission. Hagen,^*"'^^ quoting from the late 

 Dr. Bail, of Germany, asserts that the common Ento- 

 mophthora musca, or "■ Fly fungus," is none other than 

 the still more common fungus of yeast fermentation. It 

 is also said to be identical with the common " mould " 

 so annoying to housekeepers. In several papers ■*''> "*' ' ^^ he 

 enlarges considerably upon this theory, and is answered 

 in the negative by Lancaster ^^ and Prentiss,^'^ both of 

 whom state that yeast fungus is not a reliable insecticide. 



