7 2 4 SCIENCE PROGRESS 



case, but probably, as in the case of the meat or blow-fly, 

 Musca vomitoria, the egg-shell splits longitudinally and the 

 maggot pushes its way out. The length of the newly hatched 

 larva in its first stage (or instar) is seven-hundredths of an inch, 

 and it remains in this stage about twenty-four hours, when 

 it casts its skin and appears as a larger maggot three-twentieths 

 of an inch long. In this condition it remains from twenty-four 

 to thirty-six hours. After a second moult the maggot attains 

 the length of one-quarter of an inch, and in this stage it remains 

 five or six days. During its life the larva moves actively about 

 amongst its surroundings, eating up the decaying matter, but 

 avoiding bits of straw and hay. There is some evidence to 

 believe that if pressed for food larvae may devour one another. 

 After living altogether some five to seven days the larva some- 

 what suddenly turns into a dark brown pupa or chrysalis. 

 The transition takes place very rapidly — in the course of a 

 i.ew minutes — and the pupa remains enclosed in the last larval 

 skin. After another period of five to seven days in normal 

 circumstances the insect hatches out, at first running around 

 with soft and baggy wings which, however, soon stretch out, 

 harden, and dry. It is worthy of note that whereas Howard 

 found the complete metamorphosis to take ten days, and Packard 

 from ten to fourteen days, in the cooler climate of Manchester 

 Hewitt finds it takes from twenty to thirty days. The last 

 named gives some interesting particulars as to the effect of 

 the weather upon the rate of development. It is believed that 

 many flies pass the winter in the pupa state; the adult fly 

 also survives the cold weather hidden away in cracks and 

 crevices, from which it may from time to time emerge when 

 the sun shines warmly. 



When the larvae are reared in too dry manure, they attain 

 only one-half their usual size. Too direct warmth and the 

 absence of moisture and available semi-liquid food also tend to 

 dwarf them. 



A word may be said about the distribution of the insect. 

 It is practically cosmopolitan. As Mr. Austen records, "the 

 British Museum collection, though very far from complete, 

 includes specimens from the following localities : Cyprus ; 

 North- West Provinces, India ; Wellesley Province, Straits 

 Settlements ; Hong-Kong ; Japan ; Old Calabar ; Southern 

 Nigeria; Suez; Somaliland ; British East Africa; Nyassaland ; 



