q 
four hours, the larval state from five to seven days, and the pupal state 
from five to seven days. At Washington the writer has found in mid- 
summer that each female lays about 120 eggs, which hatch in eight 
hours, the larva period lasting five days and the pupa five days, making 
the total time for the development of the generation ten days. This was 
at the end of June. The periods of development vary with the climate 
and with the season, and the insect hibernates in the puparium condi- 
tion in manure or at the surface of the ground under a manure heap. 
It also hibernates in houses as adult, hiding in crevices. 
The Washington observations indicate that the larve molt twice, 
and that there are thus three distinct larval stages. 
The periods of development were found to be about as follows: E 
Fic. 6.—Homalomyia brevis: Female at left: male next, with enlarged antenna’ larva at right. 
All enlarged (author's illustration). 
first mo]t, one day; first to second molt, one day; second molt to pupa- 
tion, three days; pupation to issuing of the adult, five days; total life 
round, approximately ten days. There is thus abundance of time for 
the development of twelve or thirteen generations in the climate of 
Washington every summer. 
The number of eggs laid by an individual fly is undoubtedly large, 
averaging about 120, and the enormous numbers in which the insects 
occur is thus plainly accounted for, especially when we consider the 
abundance and universal occurrence of appropriate larval food. In 
order to ascertain the numbers in which house-fly larve occur in horse- 
manure piles, a quarter of a pound of rather well-infested horse manure 
was taken on August 9, and in it were counted 160 larve and 146 
puparia. This would make about 1,200 house flies to the pound of 
manure. This, however, can not be taken as an average, since no larve 
are found in perhaps the greater part of ordinary horse-manure piles. 
Neither, however, does it show the limit of what can be found, since 
about 200 puparia were found in less than 1 cubic inch of manure taken 
