LIFE HISTORY 7 



berg).* In 1873, Dr. A. S. Packard (1874), then of 

 Salem, Mass., studied the transformations of the in- 

 sect and gave descriptions of all the stages, showing 

 that the growth of a generation from the egg to the 

 adult state occupies from ten to fourteen days. In 

 1895, the writer traced the fly's life history, discover- 

 ing that 120 eggs are laid by a single female at a time 

 and that in Washington in midsummer a generation is 

 produced in ten days. 



Substances in Which This Fly Passes Its Early Life 



It is safe to say that the typhoid fly will breed in 

 almost any fermenting organic matter, and it is also 

 probably safe to say that if given its preference it will 

 lay its eggs on a pile of horse manure. The writer 

 once estimated that under ordinary city and town con- 

 ditions more than ninety per cent, of the flies present 

 in houses have come from horse stables or their vi- 

 cinity, and he is still inclined to think that this esti- 

 mate is probably correct. But the eggs will also be 

 laid upon the excreta of almost any animal. Cow 

 manure drying rapidly in a dry season and forming a 

 hardened caked surface is not a favorable nidus, yet this 

 fly is reared from cow manure at times. Many other 

 species of flies prefer cow manure, and a long list of 



*The best of these old papers is little known. It was published 

 at Nurenberg in 1764, and is entitled "Geschichte der gemeinen 

 Stubenfliege, Herausgeben von J. C. Keller" and covers thirty- 

 four pages of text and four plates. The real author is said by 

 Hagen to be Freiherr Friedrich Wilhelm von Gleichen (genannt 

 Russworm). 



