LIFE HISTORY 41 



Hibernation 



The typhoid fly apparently suddenly disappears with 

 the first sharp frost. It will reappear later on the 

 warmest days. With a great reduction of the tem- 

 perature of their breeding places, many larvae are killed, 

 and eggs as well. Whether the pupae in their tight 

 puparia are destroyed by a certain degree of cold does 

 not seem to be known. The adult flies undoubtedly 

 linger in warmed houses throughout the winter, but 

 that enough of them remain in active condition in such 

 locations to perpetuate the species and to start the rap- 

 idly multiplying generations of the following summer 

 seems doubtful. The adult flies undoubtedly remain 

 dormant even in warmed dwellings, and it is altogether 

 likely that some of them remain dormant throughout 

 the winter months in sheltered but cold situations. 

 Many adult insects pass the winter in this way, and 

 observations have been made which indicate that this 

 is the case with the house fly, although as a matter of 

 fact sufficient attention has not been paid in the obser- 

 vations on record of the exact specific identity of the 

 flies in question. As has been pointed out before, there 

 are so many species of flies which so exactly resemble 

 the typhoid fly to the macroscopic eye that any one 

 may be pardoned for stating that house flies have been 

 seen tucked away carefully in cracks, when a micro- 

 scopic examination would have shown that some other 

 species was concerned. 



The best observations on this general subject which 



