1873.] 141 [Packard. 



openings are very sinuous, the fissure guarded by dense projecting 

 cones. This sinuate course of the spiracles is the most prominent 

 differential character of the genus Musca. Fig. 6 shows their dispo- 

 sition in Callipliora vomitoria, and Fig. 7 their arrangement in Sarco- 

 phaga carnaria, being slenderer and situated farther apart in the 

 latter genus. 



The spiracle on the prothoracic segment (Fig. 4 c) is divided into 

 six lobules, rarely into eight. Fig. 4 d shows the end of one of these 

 lobules, with a corrugated rim, and a central slight fissure for the 

 admission of air. 



The head (Fig. 4 a) is conical, about half as long as the protho- 

 racic segment in the larva of the second stage, but much smaller 

 proportionally in the fully grown maggot. The antennae are minute, 

 conical, two-jointed, the terminal joint minute, acutely pointed. 

 Below are two fleshy tubercles, probably representing the maxillae, 

 and a single one, representing possibly the labrum, or upper lip. The 

 black horny mandibles are of the usual form of the family. 



The body of the maggot is much more transparent than in Calli- 

 pliora or Sarcophaga. The region next the sutures, between the 

 segments, is scarcely thickened, while it is conspicuously so in Calli- 

 pliora, and the tegument is smooth and shining, while in Callipliora it 

 is opake and finely shagreened. 



Length when fully grown, .25-40 inch (while C. vomitoria meas- 

 ures .55-.60 inch). It probably remains in this state about three or 

 four days. The entire life of the larva is, then, from five to seven 

 days. 



We are inclined to think that the larvae, if hard pressed for food, 

 devour each other, as of four larvae put in a bottle, only two were 

 found the day after. In the manure they eat up the decaying matter, 

 leaving the bits of hay and straw. 



Among the literally thousands of larvae which have passed under 

 our eyes, we have not as yet been able to detect an individual in 

 which the body had decidedly contracted and changed its form pre- 

 paratory to the formation of the puparium, and are inclined to 

 believe this to be a comparatively sudden act. 



For convenience in comparison, and to make this essay more com- 

 plete, we give a brief description of the larva of Sarcophaga carnaria } 

 the maggot of the common Flesh Fly, which has been known to be 

 an inhabitant of this country for about a century, as DeGeer men- 

 tions it in 1776, in his " Memoires," as having been received from 



