MUSCINM 



907 



mentation, which is also necessary. The egg takes from one to three 

 days to hatch into the larva, which lives rather less than a week, 

 and then turns into the pupa, which produces the imago. 



The whole time required is usually twelve to twenty days, and 

 never less than eight days. 



Aldridge gives the following table for India : — 



Stage. Hot weather. Cold weather. 



Eggs . . One day . . Two days. 



Larvae . . Five days . . Fourteen days. 

 Pupae . . Three days . . Five days. 



In Colombo, Ceylon, we found the development to be quick, and 

 to resemble the times given in Aldridge' s hot -weather table. 



Egg. — The imago becomes sexually mature in ten to fourteen days, 

 and eggs are laid as soon as the fourth day after fertilization, usually 

 120 to 150 eggs laid being in a batch. The egg is cyhndrically oval, 

 being broader posteriorly, and has two curved ribs along its dorsal 

 aspect. It hatchesby splitting at the dorsal portion of the anterior end. 



Larva. — The larval life is divided into periods or instars by the 

 ecdyses. 



First Instar. — The larva is 2 millimetres in length, with a slender 

 body, the head being at the narrow end, with a spiny area on the 

 anterior ventral edge of each segment, and posteriorly two stigmatal 

 openings. This stage lasts twenty-four to thirty-six hours. 



Second Instar. — The larva develops a pair of anterior spiracles. 

 This stage lasts twenty-four hours. 



Third Instar. — The larva eats vigorously for the first two days, 

 and then, ceasing to feed, still increases in size. This stage lasts 

 three to four days, and ends in pupation. The larva has a well- 

 developed alimentary canal. 



Pupation. — Pupation takes place in three to four hours, and 

 consists of the larva contracting (especially anteriorly) inside its 

 own skin, from which a puparium with rounded ends is formed. 

 Length about 6^3 millimetres, which is at first creamy-yellow, but 

 later becomes dark brown. This is a typical coarctate pupa, 

 around which the spiral locomotory pads may be seen. 



Pupa. — The pupal stage lasts about three to five days, when the 

 imago, dilating its frontal sac, ruptures the anterior end into dorsal 

 and ventral portions, the whole separating by a circular split at the 

 sixth segment. 



Fly. — -The young fly is at first underground or in the middle of a 

 rubbish-heap, through the interstices of which it makes its way to 

 the surface by the aid of its ptilinum or frontal sac. When first 

 hatched it is rather grey in colour, and has to allow its wings to 

 dry before it is able to fly. 



Habits. — ^After hatching the fly sets about to obtain food, and 

 on this point it is not particular as to the kind, as anything, from 

 typhoid faeces and dysenteric faeces to a pudding, are quite agreeable 

 to its oral lobes. It also has a liking for human sweat, much to the 



