SUBFAMILY CALLIPHORINAE 235 
quired to complete the incubation period. No hatch occurred at 
temperatures greater than 99° F., and at this temperature 7.75 
hours were required to complete the incubation period. 
Larva. First instar: Distribution and appearance of spines 
as in silvarum. 
Second instar: Distribution of spines as in silvuarum. Tuber- 
cles on border of stigmal field rather large, median pair on 
upper border not much smaller than outer; inner pair on lower 
border more than one-half as large as outer and median pairs; 
distance between inner tubercles on upper border distinctly less 
than distance between inner and outer ones but greater than 
distance from inner to median tubercles. Cephaloskeleton 
(pl.40,A) with dorsal cornua tapering to posterior end; labial 
sclerites rather short and broad. 
Third instar: Segments 2-9 each with a complete band of 
spines at anterior margin; segment 10 with the spines extending 
well up to laterodorsal surface but not joining; spines rather 
variable at posterior border of segments; segments 10 and 11 
with spines dorsally, six to eight rows Peale present on dorsal 
surface of segment 11; segment 12 generally smooth on dorsal 
surface; segment 9 with the lateral spines sometimes joined by 
a single irregular row to form a complete band. Tubereles 
outlining stigmal field very large and prominent, the outer and 
inner pairs on upper border approximately equal and less than 
twice as large as median; distance between inner and interme- 
diate tubercles not so great as distance from inner to outer 
ones; the two outer pairs on lower border larger than those on 
anal protuberances and usually larger than larger pair on upper 
border of stigmal field. Button area of spiracular plates (p1.40, 
C) rather well-developed, with a cylindrical pigmented inward 
projection below which is visible only when mounted plates are 
examined; peritreme well-developed, inward projection of peri- 
treme between inner and middle slit prominent; spiracles, in 
general, heavily pigmented as in wlustris, especially at the border 
and around slits, degree of pigmentation however varying con- 
siderably with age of specimen. Cephaloskeleton (pl.40,B) 
similar to that of silvarum and mexicana but ventral cornua 
produced posteriorly beyond hump to a greater extent than in 
these two species; labial sclerites curved slightly upward, then 
downward. 
Anterior spiracles with number of branches ranging from 6 
to 10 (In one series of 62 spiracles, Knipling (19386) found that 
4 spiracles had 6 branches, 16 had 7, 21 had 8, 18 had 9 and 3 had 
10; while in another series of 24 spiracles, 1 spiracle had 7 
