(118) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 359 



rabbits upon which to rear the larvas of C. ery throcephala, 

 I found the broken leg of alive rabbit, which had been caught 

 in a spring trap set the previous evening, a living mass of 

 small larvas, which were devouring the animal while it was 

 still alive. An enormous number of eggs are laid by a single 

 insect; Portchinski (' Osten. Sacken/ 1887) found from 450 

 to 600 eggs, though I have not found so many. With an 

 average mean temperature of 23 0. (73*5 F.) and using fresh 

 rabbits as food for the larvas, the following were the shortest 

 times in which I reared C. ery throcephala. The eggs 

 hatched from ten to twenty hours after deposition. The larvae 

 underwent the first ecdysis eighteen to twenty-four hours after 

 hatching ; the second moult took place twenty-four hours later, 

 and the third larval stage lasted six days, the whole larva life 

 being passed in seven and a half to eight days. Fourteen days 

 were spent in the pupal state ; thus the development was com- 

 plete in twenty-two to twenty-three days. I have no doubt 

 that this time could be shortened by the presence of a very 

 plentiful supply of food, as an enormous amount, comparatively, 

 is consumed. 



The full-grown larva may measure as much as 18 mm. in 

 length. The posterior extremity is surrounded by six pairs 

 of tubercles arranged as shown in the figure (fig. 12) ; there 

 is also a pair of anal tubercles. The anterior spiracular 

 (fig. 11) processes are nine-lobed. The posterior spiracles 

 (fig. 10) are circular in shape and contain three slit-like 

 apertures. In the second larval instar (fig. 9) there are only 

 two slits in each of the posterior spiracles, and in the first 

 larval instar (fig. 8) each of the posterior spiracles consists of 

 a pair of small slit-like orifices. Howard (1900) found the fly 

 on fresh human faeces, and Riley records it as destroying the 

 Rocky Mountain locust. 



C. ery throcephala is an outdoor fly, but frequently enters 

 houses in search of material upon which to deposit its eggs 

 and also for shelter. From its habit of frequenting fasces, 

 which may be observed in this country especially in insanitary 

 court-yards, and such food as meat and fruit, it is not improb- 



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