Chapter 20 



FUNG US-INSECT INTERRELA TIONSHIPS 



The studies to date on the interrelationships of fungi and in- 

 sects may be placed largely in one or the other of five categories: 



( 1 ) those dealing with insects as vectors of plant-pathogenic fungi, 



(2) those concerned with fungi that produce diseases of insects, 



(3) those involving fungi as agencies in the biological control of 

 insects injurious to crops, (4) those dealing with insects that make 

 it possible for certain species of fungi to undergo their cyclical 

 changes or developmental processes, and (5) those involving fungi 

 that are cultivated by insects for food. These studies deal with a 

 laro-e number of species in each group of organisms. For this 

 reason any account that attempts a complete review of the litera- 

 ture and a discussion of it would of necessity be voluminous, and 

 such an undertaking is beside the present purpose. Instead an 

 attempt will be made by the use of representative examples to 

 introduce each of these important fields of interest. A much more 

 comprehensive account of these subjects, to which the student is 

 referred, is contained in a volume by Leach ( 1940). 



INSECTS AS VECTORS OF PLANT-PATHOGENIC FUNGI 



This subject was briefly considered in Chapter 8, and to avoid 

 repetition some details are omitted at this point. Attention may 

 well be directed, however, to certain general features of this 

 phase of the fungus-insect relationship. It should be appreciated, 

 first of all, that a background of related evidence facilitated ac- 

 ceptance of the fact that insects are instrumental in dispersing 

 certain pathogenic fungi and in implanting them within host 

 tissues. Before 1900 it had been established that certain mos- 

 quitoes are vectors of the nematode worm, Wuchereria bancrofti, 



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