HOUSE FLIES AND BLUEBOTTLES 



199 



laying, some had already hatched, and the rest very 

 soon followed suit. As such a degree of fecundity was 

 manifested when no manure was at hand, and the 

 circumstances were therefore unfavourable, it seems pro- 

 bable that the number would have been exceeded in the 

 open under natural conditions. If a little fresh horse 

 dung be exposed at an open window during the month 

 of August, the flies will soon discover it, and may be 

 watched as they proceed to lay their eggs in all the little 

 crannies they can discover. 



The larvae are all similar in appearance (Fig. 64), 

 whitish footless grubs, known as maggots or gentles. 



FIG. 64. A, Newly hatched Larva of House fly ; B, More advanced 

 Larva of same ; C, Puparium of same. (After Packard.) 



Their shape is rather difficult to determine by observa- 

 tions on the living specimens, as the skin is soft and 

 flexible, and they are in continual motion, contracting 

 or relaxing their muscles, and thereby perpetually alter- 

 ing their form. When still, they are of a somewhat 

 conical form, the anterior end being the smaller of the 

 two. They subsist not merely on the juices, but on the 

 more solid matter of the mass of corruption amongst 



