SUBFAMILY CALLIPHORINAE 329 
bristles on fourth segment strong, erect, nearly in rows. Other- 
wise similar to male except for normal sexual differences. 
Length. 9-14 mm. 
Hough (1899) first called attention to ‘‘variation’’ in the 
chaetotaxy of this species. My own investigation of this sub- 
ject does not alter the conclusions originally drawn by him. 
He found that approximately 18 percent of the specimens showed 
some sort of chaetotaxal variation and that such variation might 
be of three kinds, (1) deficiency in size of a macrochaeta, (2) 
absence of a macrochaeta normally present, and (3) the presence 
of a macrochaeta normally absent. Some individuals among 244 
specimens examined by Hough, showed both the second and 
the third kinds of variation, and a few showed bilateral variation. 
Southern specimens sometimes have the parafaciale and, more 
rarely, the parafrontale reddish in ground color. In this, and 
in the orange or golden pollinosity, they superficially resemble 
elongata or mortuorum. Neither of these two species, however, 
has been seen from southern localities. 
Distribution. Nearctic: As far north as Ungava Bay and as 
far south as Brownsville, Tex., most abundant along the Cana- 
dian-United States border. It is an early spring and late fall 
species. In Ohio, occasional specimens may be collected on warm 
days throughout the winter in protected places. About 50 per- 
cent of all flies trapped during the spring belong to this species. 
It is present in considerable numbers during early spring, disap- 
pears during June, and reappears in late September. 
Biology, habits, and immature stages. The species is a common 
earrion-breeding form. Cured meats are often blown. 
Egg. Elongate-ellipsoidal, feebly striate longitudinally, white, 
averaging about 2.00 in length. 
As many as 25 to 50 eggs may be deposited at one time al- 
though the usual number is considerably less. Hatching occurs 
within 24 to 72 hours depending upon the season of the year 
but the exact incubation period has not been determined. 
Larva. First instar: Segments 2 to 9 evidently with com- 
plete segmental spinose bands anteriorly, segments 10 and 11 
with bands more or less restricted to ventral region, segment 
10 with band incomplete laterally. Spines very fine in structure 
but heavily sclerotized. Six tubercles on dorsal and ventral 
margins of posterior depression. Cephaloskeleton (pl. 45, A) 
with labial sclerite strongly arched, hypostomal sclerite long 
and narrow, pharyngeal sclerite with widely separated cornua. 
Posterior spiracles each with two weakly sclerotized oval aper- 
tures which are more or less united basally; no anterior spiracles, 
