560 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
some years prior to its discovery. Balch (77) published an article 
on the outbreak of the European spruce sawfly in Canada and on its 
bionomics, and Dowden (135) published an account of its status in 
the United States (fig. 153). 
Its food plants include white, red, black, and Norway spruces, and 
laboratory experiments indicate that other s species of spruce may be 
attacked. Since the discovery of the outbreak in 1930, thousands of 
square miles of spruce forests on the Gaspe Peninsula have been 
FIGuRE 152. Learn of Diprion hereyniae een at base of a Heavily defoliated 
spruce tree. 
seriously defohated and as high as 40 to 50 percent of the spruce in 
some localities has been killed. Heavy infestations began to attract 
attention in the United States in 1937, particularly in Maine, New 
Hampshire, and Vermont. Although only a small percentage of af- 
fected trees have been killed thus far in the United States, there are 
large areas where the trees have been very severely defoliated. Diprion 
her cyniae has one generation in the Gaspe region, although often a 
high percentage of the prepupal larvae in cocoons remain in diapause 
for 2 or more years. 
In most of New England and New York there are two generations 
annually, and a partial third in some years in the southern extension 
of its range when weather conditions are favorable. ‘The adults of 
the first generation emerge from early in May to early in June, de- 
pending on the climatic range, and those of the second generation 
emerge about the first week in July or later. Males are very rare, 
and reproduction takes place without fertilization. ‘The eggs are laid 
singly in slits cut in the old needles, and they hatch in a “few days. 
The young larvae begin feeding at the tips of the old needles. The 
foliage of “the older erowth is preferred, but that of the current year 
is sometimes eaten when it is full grown. The larvae mature in 
about 3 or 4 weeks, when they drop to the ground and spin their 
. —_ . 1.) ease amenArpaleatee A ah! Saint ay 
