FUNGI. 245 



It is in this direction that a knowledge of the life- 

 history of these fly-moulds may be turned to profit- 

 able account, and we do not despair of hearing, at no 

 very remote period, that, by the introduction of in- 

 fected insects, a kind of epidemic may be produced 

 at will, which will be an important agent in the hands 

 of the cultivator. Mr. Thaxter, writing of Empiisa 

 aphidis, ' says that " in greenhouses it acted as a 

 decided check to the multiplication of the Aphides, 

 yet did not spread with sufficient rapidity to render 

 smoking in the greenhouse unnecessary." Again he 

 says, "At Kittery I have found it on numerous 

 genera of aphides, and especially destructive to the 

 forms which injure the hop. In one case I observed 

 a large hop vine, some twenty feet high, completely 

 covered with aphides, which were killed off by this 

 fungus in about two weeks ; the affected hosts being 

 fastened to the under sides of the leaves, and to the 

 younger shoots in vast numbers. The destruction of 

 colonies of Aphis by this species, and another, seems 

 to be the rule rather than the exception, and is, at 

 least, of very common occurrence. An instance was 

 called to my attention in June, 1886, when I was 

 shown great quantities of aphides dying of the 

 disease on clover near the agricultural department 

 buildings at Washington. The probable agency of 

 ants in spreading these epidemics is worthy of notice, 

 as well as that of night moths, which, as well as ants, 

 are often attracted in great numbers by the sweet 

 secretion of the aphides." 



We presume that, having demonstrated that so 

 obscure and apparently simple a form of fungus life 



