214 TROPICAL MEDICINE AND HYGIENE 



decaying vegetable matter and on litter fouled with 

 ordure of horses, fowls, man, &c. 



. The larvae hatch out from the eggs in eight hours to 

 a few days. They move actively, burrow into or below 

 the surface on which they are deposited, and moult in the 

 case of M. domestica three times. They grow rapidly, 

 but only remain a short time in faeces or animal matter, 

 as when they get larger they migrate into vegetable refuse, 

 into moist soft earth, or may penetrate some distance 

 underground. In five days or much longer several 

 weeks they become quiescent and the outer skin becomes 

 smooth, hard and brown. The pupa contents fuse and 

 become a white semi-fluid mass from which the parts of 

 the fly become formed. After five to seven days or more 

 a circular cap is forced off one end of the pupal case and 

 the imago or fly emerges. If the larvae have lived under 

 favourable conditions and been well fed the flies when 

 they hatch out are full size, but when food is scanty and 

 conditions are unfavourable they are much smaller. In 

 any case, after emergence from the puparium they do not 

 increase in size. The flies become sexually mature in 

 ten to fourteen days and four days later the females are 

 able to lay eggs. 



The diet of the larvae is mainly vegetable, kitchen 

 refuse, old stable refuse and the like. In the Tropics the 

 refuse from sugar mills, megass, and any decaying 

 vegetable masses are favourite breeding places. They 

 do feed in, excrement, human and otherwise, but usually 

 leave it after a short time and burrow into the moist 

 earth beneath. In a cesspit they are not to be found in or 

 on the liquefied contents, and so cause little destruction 

 of the excreta, in this respect differing widely from some 

 of the Sarcophagidae. 



The adult, imago, whilst active probably lives only 

 about three weeks, but in cold weather much longer, and 

 may hibernate in England all through the winter. They are 

 voracious feeders and will travel considerable distances 

 for food or for suitable places and substances on which 



