536 C. 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 1s, | 
from the deposition of the egg to the exclusion of the imago, 
is eight days, which period is obtained when the larve 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—ege, 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, ete. 
6. The flies become sexually mature in ten to fourteen days 
after their emergence from the pupa, and they may begin to 
deposit their eges as early as the fourteenth day after 
emergence. Hach 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 
