2l8 



ENTOMOLOGY 



forms. Curiously enough, grasshoppers affected by this fungus almost 

 always crawl to the top of some plant and die in this conspicuous position. 

 Sporotrichum, a genus of hyphomycetous fungi, affects a great 

 variety of insects, spreading within the body of the host and at length 

 emerging to form on the body of the insect a dense white felt-like 

 covering, this consisting chiefly of myriads of spores, by means of which 

 healthy insects may become infected. Under favorable conditions, 

 especially in moist seasons, contagious fungous diseases constitute one 

 of the most important checks upon the increase of insects and are 

 therefore of vast economic importance. Thus the termination (in 1889) 



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FIG. 255. Empusa musca, the common fly-fungus. A, house fly (Musca domestica), 

 surrounded by fungus spores (conidia); B, group of conidiophores showing conidia in 

 several stages of development; C, basidium (6) bearing conidium (c) before discharge. 

 B and C after THAXTER. 



of a disastrous outbreak of the chinch bug in Illinois and neighboring 

 states "was apparently due chiefly, if not altogether, to parasitism by 

 fungi." Artificial cultures of the common Sporotrichum globuliferum 

 have been used extensively as a means of spreading infection among 

 chinch bugs and grasshoppers, with, however, but moderate success. 

 Transmission of Diseases of Plants. Not a few bacterial and fun- 

 gous diseases of plants are known to be transmitted by insects. M. B. 

 Waite proved experimentally that the bacillus causing fire blight of 

 pear, apple and other pomaceous trees is carried by honey bees and 

 other insects from flower to flower, multiplies in the nectar, and enters the 

 host plant. Bees, wasps and flies obtain the bacilli from the exudation 

 from old cankers and carry the organisms either to blossoms or to young 



