Winter is spent in the egg stage. Hatching occurs in early May and larvae are 
present until July or August, depending on focation. They are gregarious and 
usually consume all of the mature needles from one branch before migrating to 
another. Prepupae drop to the ground and spin cocoons in the duff. Adults emerge in 
early fall and deposit their eggs in slits in the round face of current season’s needles 
near the tips of well-exposed branches. The female will usually oviposit her entire 
complement of eggs on one twig. There is one generation per year (650). 
Little or no mortality results from a single defoliation because only the older 
needles are eaten, but where defoliation continues for several years a high percent- 
age of the affected trees may be killed. Overmature trees are particularly susceptible 
to damage. 
The white pine sawfly, N. pinetum (Norton), occurs on eastern white pine 
throughout the range of its host in eastern North America. Pitch, shortleaf, red, and 
Swiss mountain pines are sometimes infested. Full-grown larvae are pale yellow 
and about 25 mm long. The head is black and four rows of black spots extend from 
the head to a black spot at the posterior end. 
In the spring, the female deposits three to four eggs per needle, and the full 
complement is placed in the needles of a single twig. The larvae feed gregariously 
on both old and new needles, and when one branch is defoliated they migrate to 
another. When they reach maturity they drop to the ground, spin cocoons in the soil, 
and overwinter as a prepupa; pupation occurs in the spring. There is sometimes a 
partial second generation per year, depending on location. 
The white pine sawfly attacks trees of all sizes both in plantations and in forest 
stands. Because the larvae feed on both old and new needles, they are capable of 
completely defoliating a tree. Widespread outbreaks occur occasionally, whereas 
local ones are reported almost every year. The egg parasite, Closterocerus 
cinctipennis, 1S Sometimes an important natural control agent (/0/7/). 
The balsam fir sawfly, N. abietis (Harris), occurs from coast to coast in 
southern Canada and Northern United States. Its favored host is balsam fir but it 
also attacks black and white spruces. Full-grown larvae are dark green and are from 
18 to 25 mm long. The head is black and the body is marked with six longitudinal 
dark stripes or bands on the back, the lowest of which may be broken up into small 
dots or spots. 
Winter is spent in the egg stage and hatching occurs in May or June. Newly 
hatched larvae feed gregariously on old needles, eating only parts of the needle. 
Feeding is completed in about 1 month. The mature larvae then spin tough, silvery 
or light-brown cocoons on the needles or in the litter on the ground. Adults appear 
from late July to early September and lay their eggs singly in slits cut in the edges of 
the needles. There is one generation per year. 
Balsam fir growing in open stands, in pastures, along lakeshores in Ontario, and 
on islands off the coast of Maine is often heavily defoliated. Trees are seldom killed 
by a single defoliation but some are killed by repeated defoliations. Spruce trees in 
farm shelterbelts and ornamental plantings in the Prairie Provinces of Canada also 
have been damaged. The introduced parasite, Dahlbominus fuscipennis (Zet- 
terstedt), has destroyed up to 40 percent of cocoons in the duff in Maine. Cocoons 
spun among the needles on the trees in the same stands escape parasitization. 
Neodiprion abbotii (Leach) has been recorded in Ontario, Quebec, Wisconsin, 
Virginia, North Carolina, South Carolina, Georgia, and Florida. Its hosts are listed 
as loblolly, slash, longleaf, shortleaf, and red pines. The full-grown larva has a 
brown to black head with a light spot on the frons, and the thorax and abdomen are 
390 
