DIPTERA. 131 
The fly appears in early summer (June or July for Texas), the time 
doubtless depending on the latitude, it having passed the winter as 
adult presumably either in a latitude free from extreme cold or a pro- 
tected location in houses. There is no impossibility of the migration 
Fic. 64.—Compsomyia macellaria: adult, wings at rest—enlarged (after Francis). 
of these flies from localities several hundred miles south of the place of 
their appearance in early summer, as aside from the powers of flight 
they could easily be transported on boats or cars. I know of no obser- 
vations, however, to establish such a means for their distribution. 
In depositing its eggs it selects some wound or decaying matter and 
lays a mass of eggs at once; at least three or four hun- 
dred may be deposited by a single female within a space 
of a very few moments, and the same fly may oviposit 
at different times and in different places hundreds or 
even thousands of eggs. ; 
The eggs are cylindrical, like those of other flies, 
about 1 mm. in length, white. ‘Under the microscope : 
the eggs show a prominent ridge on one side.” (Weed.) ae 
The eggs hatch within a few hours. Francis says: vie w—enlarged 
(after Francis). 
My present opinion is that if the eggs are laid in a moist place 
and on a warm day it requires less than one hour; whereas if laid in a dry place 
they seem to dry up and lose their vitality. 
Weed considers the time required for hatching about nine hours. 
The idea that they may be deposited in living condition is combated 
by all careful observations. The larva, or maggot, is a whitish footless 
grub, rather slender and quite active, burrowing into the tissues of the 
affected animal or into the mass of putrid flesh or decaying matter that 
furnishes it food. They grow rapidly and mature in five or six days 
(Weed) or about a week (Franeis). When mature they escape from 
the wound they have infested or wriggle away from the mass of matter 
T= 
