DISEASES CAUSED BY FUNGI 



63 



and at the present day have become so liighly specialized tliat they 

 are bound down for their existence to the presence of a single kind 

 of host-plant. 



In addition to victimizing plants, fungi are also parasitic on 

 members of the animal kingdom, insects perhaps being the greatest 

 sufferers, myriads of insects being destroyed annually by parasitic 

 fungi. The white halo that surrounds a dead fly on a window- 

 ])ane is a fungus. Most insects are infected by spores while alive. 

 The spores germinate and form a mycelium which slowly kills the 



Cordyceps, a parasite fungus growing on a caterpillar. 



insect. At a later stage the fungus produces its fruit on the surface 

 of the body of its victim. The fungus fruit often assumes the form 

 of a club ; a common and beautiful club-shaped fungus, one to two 

 inches high, and of a beautiful orange-red colour, is not uncommon, 

 apparently growing out of moss or amongst dead leaves. If the 

 fungus is removed very carefully it will be found attached to the 

 chrysalis of an insect. In New Zealand, many of the huge cater- 

 pillars that abound there are attacked by fungi, the mycelium of 

 which graduahy completely fills the body of the caterpillar, and 

 forms a dense, white, woody mass. The clubs that spring from 

 these caterpillars are sometimes six inches in length. 



