64 THE HOUSE FLY— DISEASE CARRIER 



continually reproduced by budding or division until 

 the insect is more or less completely filled with them. 

 These fragments are called hyphal bodies. They con- 

 tain a highly concentrated, fatty protoplasm and are 

 capable of subsequent and often very extended develop- 

 ment. 



When the mass of these bodies has been completed 

 and the death of the insect attacked has occurred, the 

 fungus may proceed at once to the completion of its 

 development under proper conditions of temperature 

 and moisture, but if these conditions are absent a rest- 

 ing stage ensues in which the contents of each hyphal 

 body becomes surrounded by a single wall which in- 

 creases in thickness as the resting stage continues. The 

 fungus may remain dormant in this condition for a 

 considerable period. Doctor Thaxter has observed the 

 hyphal bodies germinating after several weeks, and 

 thinks that they probably retain their vitality for a 

 much longer period, and may perhaps hibernate under 

 certain circumstances. 



When a moist atmosphere and a sufficiently high 

 temperature come they germinate with great rapidity. 

 With the common house fly fungus (Empusa musccc) 

 a slight change in the amount of atmospheric moisture 

 is sufficient to bring about germination. This, accord- 

 ing to Thaxter, is very noticeable on the seashore, 

 where slight changes of the wind from the water or 

 from the shore bring about a very rapid and noticeable 

 effect upon the flies thus parasitized when watched in 

 the ordinary atmosphere of the house. With other 



