There are also two light and one intense green or black stripes 
on each side. 
Winter is spent in the egg stage and hatching occurs from 
early April to mid-May. The larvae feed gregariously on previous 
year’s foliage (fig. 180) and devour all of the needles on one 
branch before moving to another one. New needles are never 
eaten. Larvae may also feed on the bark of new shoots. This may 
result in shoot deformation or death (777). When an entire tree 
is defoliated before the larvae reach maturity, it is vacated and 
the larvae craw! to other trees to feed. Full-grown larvae either 
drop to the ground and spin tough, light to dark golden brown 
cocoons in the duff, or they spin them in protected locations on 
the tree. Pupation occurs during late August or early September 
and the adults appear from early September to late fall. Eggs are 
laid in slits cut in the edges of current year’s needles in needle 
clusters near the end of a branch. Six to eight eggs are usually 
laid in a single needle and about 10 to 12 needles in a single 
cluster are usually infested. There is one generation per year. 
F-519945 
FIGURE 180.—Colony of lar- 
vae of the European pine 
sawfly, Neodiprion  serti- 
fer. Larvae hanging head 
downward were killed by 
a polyhedral virus. 
Trees defoliated by the European pine sawfly are seldom killed, 
since the new foliage is never eaten and the tree is never entirely 
stripped of its foliage. Bark feeding may cause some twig mor- 
tality but it is not serious. Losses in height and diameter growth 
may be severe however, especially following repeated defoliations. 
Damage is most severe to Scotch pines grown as Christmas trees 
in plantations. 
During the late thirties and early forties, colonies of the two 
European parasites, Dahlbominus fuscipennis (Zett.) and Hwxen- 
terus abruptorius (Thunberg), were received from Canada for 
release in eastern infestations of this sawfly. D. fuscipennis be- 
came established in New Jersey and within a few years became 
rather abundant locally (299). E. abruptorius also became estab- 
lished in New Jersey. So far, neither species has given adequate 
control. A supply of a European polyhedrosis virus of the sawfly 
was also received from Canada for use in its control (66). It has 
proved to be very effective when applied as a spray either by 
aircraft or by knapsack or hydraulic sprayers. Lyons (466) re- 
448 
