The introduced pine sawfly, D. similis (Hartig), was first recorded in New 
Haven, Conn., during 1914, and spread to western Wisconsin by 1944 (247). It was 
first found in North Carolina during 1977 and by 1981 had been detected in two 
distinct outbreaks covering 24,000 square kilometers in North Carolina, Tennessee, 
and Virginia (339, 474). It is now known to occur from Maine to North Carolina, in 
the Central and Lake States, and in southern Ontario and Quebec. Eastern white 
pine is the favored host but Scotch, jack, red, and Swiss mountain pines are 
commonly reported secondary hosts. Shortleaf and Virginia pines are also attacked 
but are not considered to be threatened. 
Full-grown feeding larvae (fig. 185) are about 20 to 25 mm long, with shiny 
black heads. The body has a double black stripe bordered by yellow along the 
dorsal midline, and the sides are dark with numerous rounded yellow and white 
spots. Ventrally the larvae are pale yellow. Cocooned larvae have gray heads; the 
body is pale gray-green and bears markings similar to those of feeding larvae, but 
much lighter. The pupa is light green. Cocoons are cylindrical with rounded ends 
and relatively thick, tough walls that vary from very light to dark brown in color. 
Winter is spent as cocooned larvae. Pupation occurs in early spring and adults 
emerge principally during May and early June. The females produce a potent sex 
attractant (239). Eggs are laid in rows of about 10 per needle, each deposited in a 
slit cut into the edge of the needle (fig. 186). Young larvae feed gregariously; older 
larvae, singly. First-generation larvae prefer to feed on previous year’s needles, 
while larvae of the second generation eat both old and new needles. Young larvae 
eat only the outer, tender parts of needles; older larvae consume entire needles and 
will feed on twig bark when most of a tree’s foliage has been consumed. Both first- 
and second-generation cocoons are spun in crown foliage, at the base of small 
branches, in bark crevices on the trunk, on host or nonhost trees, shrubs, grasses, 
or other understory objects. Pupation occurs mainly during July, and second- 
generation larvae feed through September. Small numbers of third-generation adults 
(mostly males) are reported to emerge during some years in Wisconsin, but most 
F-531260 
Figure 186.—Introduced pine sawfly, 
Diprion similis, ovipositing in 
eastern white pine needles. Eggs 
of this species are covered with a 
pulpy mass. 
Courtesy H. C. Coppel, Univ. Wis. 
Figure 185.—Larvae of the 
introduced pine sawfly, Diprion 
similis. 
395 
