146 THE BLOWFLIES OF NortH AMERICA 
less V-shaped group extending upward on outer side; border of 
posterior cavity armed with numerous rows of three or four 
spines. Cephaloskeleton (pl. 35, G) with labial sclerites smaller 
than in americana; pharynx with longitudinal ridges, whereas in 
americana it is smooth; pharyngeal sclerites large with dorsal cor- 
nua slightly elevated; pigmented strip of varying extent just 
above dorsal cornua in more mature third-instar larvae; length of 
cephaloskeleton from 1.43-1.63 mm. (average of 10, 1.56 mm.). 
As the eggs hatch, in myiasis cases, the emerging larvae be 
* gin to feed upon necrotic tissue, migrating considerably from 
one place to another. They have no definite type of attack in 
carcasses. They are active when internal temperatures of the 
carcass reach 41-50° F., according to Deonier (1940). In wounds 
larvae of this species do not form the typical pocketlike injury 
characteristic of americana, but often migrate into the wool or 
hair (Fig. IX) about the wound. On long-fleeced sheep the lar- 
vae have a tendency to feed outside the wound in the wool; in 
short-haired animals they tend to feed in the wound. They at- 
tain maturity in from 6 to 20 days, then migrate from the car- 
eass or drop from the wound and then burrow into the soil or 
crawl into shelter to pupate. 
Puparium. Similar to that of americana but not quite so 
large and not so barrel-shaped. It averages about 7.6 mm. in 
length and 2.8 mm. in diameter and has the external characters 
of the mature larva. Melvin, in Laake et al. (1936), found that 
macellaria larvae pupated in about 1.385 inches of clay soil, 1.41 
inches of heavy black soil, and 1.76 inches of sand, and that 5 ~ 
inches was the maximum depth at which pupation occurred. He 
found the length of the pupal stage to be approximately half 
that of americana under conditions in which the pupae of both 
were exposed to the influence of outside weather factors. 
Adult. The preoviposition period in macellaria is from 3 to 
18 days according to Bishopp (1917, p. 325). Females oviposit 
principally upon carrion, occasionally upon live animals. One 
female may deposit as many as eight egg masses, the period be- 
tween depositions ranging from one to seven days. The average 
interval seems to be from two to four days. Gravid females will 
deposit enormous numbers of egg masses upon a single ecar- 
eass; Babeock and Bennett (1921, p. 5) stated, ‘‘One will often 
see a mass of eggs half as large as a man’s fist where many screw- 
worm flies have been depositing.’’ Part of such a mass might 
have been composed of eggs deposited by other calliphorids, for 
example, Phormia regina or species of Phaenicia; but in south- 
west Texas, where these observations were made, most of the 
