second-generation sawflies overwinter as diapaused larvae within cocoons. Because 
of its variable development, all stages of this sawfly may be present at the same time 
during the summer (24/, 474, 846, 1325). 
Defoliation is usually most severe in the upper half of tree crowns, but heavily 
infested trees may be completely defoliated in one season. When this happens late 
in the season after the winter buds have formed, many branches and occasionally 
trees may be killed. 
Some factors in natural control include very low or rapidly fluctuating tem- 
peratures or heavy rainfall during the egg and early larval stages, bird predation of 
cocooned larvae, and the establishment of three European parasitic wasps. The 
ultimate-stage larval parasitoid, Exenterus amictorius (Panzer), and two cocoon 
parasitoids, Dahlbominus fuscipennis (Zetterstedt) and Monodontomerus dentipes 
(Dalman), are important control agents in Wisconsin (24/). Suppression of the 
introduced pine sawfly to low population levels in North Carolina was achieved by 
1982, primarily through mass-rearing and augmentative releases of M. dentipes 
(474). 
A comprehensive review of the European and North American literature on D. 
similis is available (24/). 
The genus Gilpinia is represented by two species in the United States and Canada 
and both are of foreign origin. 
Gilpinia frutetorum (F.) was discovered in North America in Massachusetts and 
Rhode [sland in 1932, and now occurs in Quebec, from Maine south to New Jersey, 
Pennsylvania, Wisconsin, and Minnesota. Its favored hosts are red and Scotch 
pines, but it may also attack various other hard pines. Full-grown larvae are light 
green with reddish-brown heads and are about 20 mm long. The body is marked 
with six longitudinal dark-green stripes, two on the dorsum and two on each side 
(fig. 187). 
Winter is spent as a cocooned prepupa and pupation occurs in the spring. Adults 
appear from late May to late July. Eggs are laid in slits cut in the needles. The larvae 
feed singly, preferably on the older needles. Because of their greenish color they 
blend into the background and are difficult to see. The first sign of infestation 
usually is the presence of frass and green needle fragments on the ground beneath 
the tree. Heavy infestations occur occasionally in pine plantations (/06/). 
The European spruce sawfly, G. hercyniae (Hartig), was first recorded in North 
America near Ottawa, Canada, in 1922. It has spread throughout the eastern spruce 
F-519578 
Figure 187.—Larvae of Gilpinia frutetorum. 
396 
