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THE POPULAR SCIENCE MONTHLY. 



DEVELOPMENT OF THE HOUSE-FLY. 



By M. H. KOBSON. 



THE following remarks on the development of the house-fly are 

 based on actual observation, and the appended sketches were 

 made by Mr. G. Harkus from the microscope, with the aid of a Beales 

 reflector. 



Mr. Harkus, with whom I experimented simultaneously, was fortu- 

 nate, or the reverse, in having the required ova brought to him in this 

 way : A fly having gained access to a cold joint of lamb considerately 

 left a sufficient supply for his examination. The objectionable part of 

 the arrangement was probably counterbalanced by his being enabled to 

 fix the time of deposition with tolerable certainty. This was on July 

 28th. The eggs (one of which is represented in Fig. 3, its diameter 

 one thirtieth of an inch) were placed with a portion of the meat in 

 a glass vessel, and next day the maggots had emerged as in Fig. 4 

 (diameter one twenty-fifth of an inch), where the ramifications of the 

 tracheal system may be traced. 



The warm weather, coupled with the indoor heat, matured the 

 larva rapidly, the change from maggot to chrysalis (Fig. 2) being ap- 

 parent at each observation, some having assumed this state on July 



Piq. 1. The House-Fly {Musca domestka), magnified. 



30th. The perfect stage was reached and the fly emerged on August 

 5th, or eight days from the deposition of the ova (Fig. 1). 



This was a week in advance of the result obtained in my experi- 

 ment, which I preferred to conduct out of doors. A piece of raw liver 

 was exposed, which soon had eggs enough attached to it. It would 

 appear that the fly has to some extent the power of withholding the 



