266 Tuer BLOWFLIES oF NortH AMERICA 
less area, but sometimes with a complete band of spines; seg- 
ment 9 with spines extending from ventral to laterodorsal sur- 
faces but absent on dorsum; generally restricted to ventral sur- 
face on segment 10; posterior borders of segments 11 and 12 with 
complete bands of spines, these narrowed to one or two irregular 
rows, or sometimes absent, on dorsal surface of segment 10. 
Distance between inner pair of tubercles on upper lip approxi- 
mately equal to distance between inner and median pairs and 
never equal to distance between inner and outer pairs; anterior 
spiracles more often with seven to nine branches; cephaloskeleton 
(pl. 41, E) as illustrated. 
Third instar: Wardle (1930) called the third stage the pre- 
pupal stage and defined it as a ‘‘non-feeding, edaphic, mobile 
phase of the blowfly life cycle which intervenes between the ~ 
second larval moult and the commencement of pupation. It is a 
stage spent within the soil or close to the soil surface.’’ 
Average length 14 mm.; deep cream tinged with purplish; 
comparatively slender and cylindrical, all segments except cepha- 
lie of about same circumference; second segment constricted be- 
hind cephalic segment; ventral pads on abdominal segments with 
minute spines; spiracular pit with almost perpendicular face, the 
posterior spiracles on posteriorly directed face. Distribution of 
spines rather variable. Segments 2-8 each provided with com- 
plete encircling band of spines at the anterior margin; segment. 
9 also with spines sometimes forming a complete band on dorsal 
surface, but these more usually absent for a short space; seg- 
ment 10 with or without one to two irregular broken rows on 
lateral surface; distribution of spines apparently more uniform 
in series from a single egg mass; in one series a large majority of 
the larvae with a complete band of spines on segment 9, in an- 
other a few larvae provided with a complete band of spines on 
this segment; posterior border of segment 11 with about four 
rows of spines; segment 10, bare on dorsum, spines usually re- 
stricted to the ventral and ventrolateral surfaces; segment 12 
smooth on dorsal surface. Tubercles outlining stigmal field and 
on anal protuberance large, those on latter much larger than on 
former, comparative size of tubercles on border of stigmal field 
as in illustris, distance between inner tubercles on upper border 
approximately equal to distance between the inner and median 
ones and never separated by a distance equal to that between 
the inner and outer ones. Posterior spiracles (pl. 41, G) with 
usual form, peritreme narrow, yellowish, never black or dark 
brown, inner projection of peritreme usually faint and poorly 
developed if present, but often absent. Cephaloskeleton (pl. 41, 
