DIPTERA. 119 
The time and method of the deposition of the eggs were for some 
time a puzzle, but it was clearly shown in the investigations of the 
Division of Entomology that the eggs are placed in fresh cow manure 
in daytime, mostly between 9 a.m.and 4p.m.,and that in laying them the 
females dart only for an instant from the cattle, immediately after the 
dung is passed, and that within a little more than a minute afterward 
all had returned to the animal. They are laid singly, and never in 
clusters, and usually on their sides on the surface of the wet dung; 
seldom inserted in cracks. (Fig. 57, a.) 
Egg.—Length, 1.25 mm. to 1.37 mm.; width, 0.34 mm. to 0.41 mm. Shape, 
irregular oval, nearly straight along one side, convex along the other. General 
color, light reddish brown, lighter after hatching. General surface covered with a 
hexagonal, epithelial-like sculpture, each cell from 0.027 mm. to 0.033 mm. in length 
by about half the width. In the unhatched egg, even in those just deposited, a 
long, rather narrow, ribbon-like strip is noticed along the entire length of the flat- 
tened side, rather spatuloml in shape. In hatching this strip splits off, remaining 
attached at one end, and the larva emerges from the resulting slit. 
Larva.—After the eggs hatch, the larve descend into the dung, remaining, how- 
ever, rather near the surface. 
Newly hatched larva.—Length, 2.45 mm., and greatest width, 0.48 mm. Color, pure 
white. Joints of segments rather plainly marked, venter with slightly elevated 
ridges at ends of abdominal segments, the ridges with delicate sparse rugosities. 
Resembles in main full-grown larva. 
Full-grown larva.—Length, 7 mm.; greatest width, 2 to 2.5 mm. Color, dirty 
white. Antenne, 3-jointed, last joint pointed. Head with a lamellar or ridged 
structure shown in figure; divided by cleft at tip; skin behind lamellar struc- 
ture coarsely granulated, while that of thoracic and abdominal joints is nearly 
smooth. Thoracic stigmata pedunculate with six pedunculate orifices. Ridges on 
venter of abdominal joints not strong, fainter than in young larva. Anal stigmata 
q large, slightly protruding, very dark brown, nearly round, flattened on proximal 
borders, slightly longer than broad, 0.14 mm. in length, with one central round 
opening, and a series of very delicate marginal tufts of cilia, four tufts for each 
spiracle, each issuing from a cleft, but none on the proximal edge. Anal segment 
below with a dark yellow chitinous plate showing six irregular paired tubercles; 
the surface of the skin surrounding the plate rather coarsely granulated (fig. 57, D). 
The larval stages are passed in from four to six days. 
Puparium.—W hen ready to transform, the larve evidently descend from the dung 
into the ground below from a half to three-quarters of an inch. Actual observa- 
tions were made on larve in dung in breeding cages where the soil was fine sand, 
affording ready entrance to the larve. Where the dung has been dropped upon hard 
ground the probabilities are that they will not enter so deeply, and may indeed 
transform upon the surface of the ground at the bottom of the dung. 
Description.—The puparium is from 4 mm. to 4.5 mm. in length, by 2 mm. to 
2.5mm. in width, regularly ellipsoidal, the head rather more pointed; dark brown 
in color. The segments are plainly separated. The anal stigmata are darker in 
color than the rest of the skin; are slightly protruded and preserve the same shape 
as in the larva. The central opening is still visible, as are the slight indentations 
of the border. The ventral plate, noticed at the base of the anal segment of the 
larva is still noticeable as a series of tubercular elevations. (See fig. 57, ¢.) 
The pupa stage may last from five to eight or ten days, so that the 
full time from egg deposition varies from ten to seventeen days, esti- 
mated for the average as about two weeks. As the flies doubtless 
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