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COURTESY CONN. AGR. EXPT. STA. 
FIGURE 188.—Larvae and cocoons of 
the larch sawfly, Pristiphora erich- 
Sonii. 
‘ 
F-495242 
FIGURE 190.—Dorsal and lateral 
views of larvae of the yellow- 
headed spruce sawfly, Pikonema 
alaskensis. 
F-519576 
FIGURE 189.—Larvae of the moun- 
tain ash sawfly, Pristiphora 
geniculata. 
cocoons in the duff or top soil. There is one generation per year 
(554). 
The yellow-headed spruce sawfly is most injurious to shade 
trees and ornamentals, to nursery stock, and to young trees in 
plantations, as well as naturally regenerated cutover areas, in 
shelterbreaks, and windbreaks. Open-grown trees older than 5 
years are especially susceptible to injury, the majority being 
killed by 3 or 4 consecutive years of moderate to heavy defolia- 
tion. Trees in natural or closed stands are practically immune to 
attack and damage. 
The green-headed spruce sawfly, Pikonema dimmockii (Cres- 
son), also occurs from coast to coast in southern Canada and 
from Maine to Idaho, and feeds on various species of spruce. 
Populations are usually low and apparently cause little injury. 
460 
