256 TEXT-BOOK OF FUNGI 



substratum. Although in some instances the fungus 

 would appear to produce little or no injury to the insect 

 host, yet in most cases death is the outcome of the para- 

 sitism. In many instances the mortality to forms of insect 

 life caused by members of the Entomophthoreae is very 

 great and widespread, and as such mortality occurs 

 amongst insects destructive to plants or animals, a correct 

 knowledge of the life-history of this group of fungi be- 

 comes important from an economic standpoint. 



Thaxter, an American mycologist, who has paid special 

 attention to this group of fungi, describes an epidemic 

 caused by these fungi as follows : 



' I have observed two epidemics caused by this species 

 \Empusa {Entomophthora) sphaerospermd\, one among 

 certain small flies in a wood near marshy ground at 

 Kittery, Me., where the hosts occurred in considerable 

 numbers, fixed by the fungus on the under side of the 

 lower leaves, a few feet from the ground. The second 

 instance occurred in two orchards in the same locality, 

 where the hundreds of the previously mentioned epidemic 

 were replaced by tens of thousands, the host in this in- 

 stance being the leaf- hopper (Typhlocyba mail and rosae\ a 

 pest only too well known to cultivators of roses. Having 

 first observed it in some abundance on roses in a garden, 

 I was led to make an examination of adjacent apple 

 orchards, and found the lower branches of the trees 

 literally covered with the affected hosts, a dozen or more 

 being often fastened to a single leaf.' 



The same author also describes Entomophthora aphidis 

 as producing a similar wholesale destruction of the aphis 

 so injurious to the hop plant. 



Distribution general. 



