CHAPTER XXV 

 Fungous Diseases of Insects 



DID you ever notice on the window pane in autumn a 

 dead, swollen fly sticking to the glass by its tongue and 

 feet, with a circle of white, powdery dots about it resem- 

 bling a halo, and with an abdomen so swollen that it 

 seems to be made up of alternating black and white rings ? 

 If you break the fly apart, you will probably find it brittle, 

 and with a lens you can see whitish threads inside. 



This fly is the victim of a parasitic fungus somewhat 

 similar to many of the fungi that cause disease and death 

 in the higher plants. The white dots are the spores of 

 the fungus thrown out from the fruiting threads that have 

 developed in the body. By means of these spores other 

 living flies may catch the disease and die. 



One who understands how dangerous flies are as carriers 

 of the germs of typhoid fever and other diseases of man- 

 kind will not regret that they themselves are thus destroyed 

 by this parasitic fungus. Consequently it is easy to ac- 

 knowledge that we have friends as well as foes in the great 

 group of fungi. 



The halo-producing fly parasite is a typical example of 

 the family of Insect-killing Fungi (Entomophthoreae). It 

 belongs to the genus Empusa, so called because the Greeks 

 in ancient times used the name Empusa when they fancied 

 they saw "a weird specter of constantly changing shape." 



A parasitic fungus closely related to that which attacks 

 the house fly often occurs in colonies of aphides or plant 



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