SUBFAMILY CALLIPHORINAE 311 
mm. in length, and are translucent creamy-white when first 
molted but gradually yellow with maturity. All spines minute, 
usually single-pointed (rarely with two or three points) and 
hghtly pigmented except at tip. Cephalic segment with branch- 
ing oral grooves which radiate from the oral opening. Segments 
2 to 9 anteriorly with complete spinose bands, anterior bands 
not complete dorsally on segments 10 to 12; segments 6 to 11 
posteriorly with spinose bands, these complete on segments 9 to 
11; segment 12 with a large area of ventral spines. Anterior 
spinose bands composed of posteriorly directed spines, posterior 
bands composed of anteriorly directed spines; spines in posterior 
bands usually smaller and with sharper tips than spines in 
anterior bands. Anal protuberance surrounded with spines. 
Posterior cavity (pl. 44, A) outlined by six tubercles on upper 
and eight tubercles on lower margin; inner tubercles on dorsal 
margin separated by a space equal to that from inner to outer 
tubercles, the median tubercle sometimes nearer the outer than 
to the inner tubercle; ventrally, two minute tubercles situated 
close together and dorsally to two inner tubercles, outer and 
median tubercles largest, median tubercle situated closest to 
outer, and dorsally to a line drawn between inner and outer 
tubercles. Anterior spiracles as in preceding instar; posterior 
spiracles (pl. 44,F) each with three well-defined slitlike orifices, 
the ‘‘button’’ obvious and the peritreme complete. Cephalo- 
skeleton (pl. 44, E) with hypostomal sclerite short, stout, 
strongly sclerotized and pigmented; dorsal cornua elongate, ven- 
tral cornua with obvious ventral longitudinal grooves. 
Bishopp (1915) found the larval stage of this species to be 
from three to four days in duration in eastern Texas, and Brown 
(1936) noted it to be from 6.5 days to 8.75 days in southern 
Canada at 28 degrees C. and 70 percent relative humidity. The 
latter author observed that mature larvae begin to migrate from 
their food in about 4.5 days and that pupation usually occurs 
in 7.5 days after oviposition. 
Parker (1922) suggested that this species was able to repro- 
duce by paedogenesis during the fall months. Keilin (1924) dis- 
proved the assumption of either paedogenesis or polyembryony. 
The latter author states ‘‘Dissections and breeding experiments 
involving the examinations of 661 larvae have clearly proved that 
neither paedogenesis nor polyembryony occurs in the larvae.’’ 
Roy (19387) described the morphology and physiology of the 
larva of vicina, and discussed the difference between the mor- 
phology of larvae which are clearly saprophagous and those 
which are clearly parasitic. Ratcliffe (1935) gave experimental 
