506 C. GORDON HEWITT. 
that oviposition may take place as early as the fourth day ; 
Taschenbere (t.c.) states that the female lays on the eighth 
day after copulation. When about to deposit its eggs the fly 
alights on the substance which it selects as a suitable nidus 
and, if possible, crawls down a crevice out of sight. There 
it lays its eggs in clumps; they are usually placed vertically 
on their posterior ends and closely packed together. During 
a single day, if undisturbed, a fly may lay the whole batch of 
egos which are mature in the ovaries and which may number, 
I find from actual count, from 120—150. 
2. The Egg.—The egg of M. domestica (PI. 30, fig. 1) 
measures 1 mm. in length, sometimes slightly less. It is. 
cylindrically oval; one end, the posterior, is broader than the 
other, towards which end the egg tapers off slightly. The 
outer covering or chorion is pearly white in colour, the 
polished surface being very finely sculptured with minute 
hexagonal markings. Along the dorsal side of the egg are 
two distinct curved rib-like thickenings having their concave 
faces opposite. In the hatching of the eggs which I have 
observed, the process was as follows:—A minute split ap- 
peared at the anterior end of the dorsal side to the outside of 
one of the ribs; this split was continued posteriorly (fig. 2), 
aud the larva crawled out, the walls of the chorion collapsing 
after its emergence. The time of hatching varies according 
to the temperature. With a temperature of 25°C.—35°C. the 
larvee hatch out from eight to twelve hours after the deposition 
of the eggs; at a temperature of 15°C.—20°C. it takes about 
twenty-four hours, and if kept as low as 10°C., two or three 
days elapse before the larvee emerge. 
3. The Larva.—First larval stage or first instar. 
—The newly-hatched larva (fig. 8), measures 2 mm. in length. 
It contains the same number of segments as the mature larva 
and at the anterior end of the ventral surface of each of the 
posterior eight segments there is a spiny area (sp.). The 
posterior end is obliquely truncate, and bears centrally the 
only openings of the two longitudinal tracheal trunks, each 
trunk opening to the exterior by a pair of small oblique slit- 
