(96) 



536 0. GORDON HEWITT. 



such as vegetable refuse from kitchens and decaying grain ; 

 rotten fruit, as bananas, apricots, cherries, plums, peaches and 

 melon-slices ; in spent hops ; in waste food-stuffs, as bread 

 moistened with milk, boiled egg, broth ; bad meat and dead 

 animals. 



2. The most important factor in the development is tem- 

 perature; a high temperature accelerates the development. 

 Others factors concerned in the development are the nature 

 of the food and moisture, the effects of which are shown. 

 Fermentation is also an important factor in development, as 

 first shown by de Geer. 



3. The shortest time occupied in the development, that is, 

 from the deposition of the egg to the exclusion of the imago, 

 is eight days, which period is obtained when the larvae are 

 incubated at a constant temperature of about 35 C. ; under 

 unfavourable conditions the development may extend over 

 several weeks. 



4. There are three larval stages, and the shortest times 

 obtained for the development of the different developmental 

 stages is egg, from deposition to hatching, eight hours ; 

 first larval instar, twenty hours; second larval instar, twenty- 

 four hours ; third larval instar, three days ; pupal stage, 

 three days. 



5. House-flies usually breed from June to October, but if 

 the necessary conditions of temperature and suitable food are 

 present they are able to breed practically the whole year 

 round ; these conditions are not, as a rule, satisfied during 

 the winter months, except in such places as warm stables, etc. 



6. The flies become sexually mature in ten to fourteen days 

 after their emergence from the pupa, and tfiey may begin to 

 deposit their eggs as early as the fourteenth day after 

 emergence. Each fly lays from 120-150 eggs in a single 

 batch, and it may lay as many as six batches during its life. 



7. The anatomy of the adult larva is described in the 

 second portion of the paper. The body of the larva is con- 

 sidered to be composed of thirteen segments, of which the 

 remnant of the cephalic region or pseudo-cephalon forms the 



