THE HOUSE-FLY 3 



through the surface layers. Fortunately they were not. 

 It was only in the moist, warm portions of the piles near 

 the surface that maggots were present. But with these 

 conditions enough flies were bred in the two piles of 

 manure to stock the rooms of a very large building. 



Apropos of the possibilities of manure in the produc- 

 tion of house-flies, L. O. Howard gives even more 

 surprising figures. He took a quarter of a pound of 

 horse manure, well infested, and found within it 160 

 maggots and 146 puparia which would produce about 

 1200 flies to a pound of manure. 



Again, during September, the manure that had been 

 allowed to accumulate for several months was removed 

 from a certain large cowshed at the old University barns. 

 The wagons were backed under the shed and loaded. 

 When drawn out they had to pass over a plank twelve 

 inches wide that served as a threshold of the double 

 doors. After the work had been going on some time, 

 W. A. Riley gathered the puparia that had accumu- 

 lated on one square foot of this plank. By weighing the 

 whole mass and a known number of the puparia, he was 

 able to determine that the square foot of surface had 

 yielded 7000 puparia. In a subsequent examination, the 

 plank was found, for its whole length, black with them, 

 and the remaining manure on the floor of the shed was 

 full of the dark brown puparia. 



THE LIFE HISTORY OF THE HOUSE-FLY 



The house-fly, like its remote cousin, the mosquito, has 

 four distinct stages in its life history, egg, larva or " mag- 

 got," pupa, and adult. The house-fly, in all of its phases 



