INSECT ENEMIES OF EASTERN FORESTS OMe 
Quebec, and Ontario. Field observations indicate that the larvae of 
this insect will survive only on the foliage of American or European 
mountain-ash. 
The adults emerge during 
the latter half of May and 
in June, the dates varying 
in different localities and 
with the season. Eggs are 
deposited in shts cut by the 
female near the edges of the 
leaves. Newly hatched 
larvae may be found from 
early in June to the middle 
of July, and they reach full 
growth from early in June 
to the middle of August. 
The newly hatched larvae 
feed between the veins, 
skeletonizing the leaves, but Ficure 161.—The mountain-ash sawfly (Pris- 
after a few days they usu- tiphora geniculata), lateral and dorsal 
ally eat all of the leaf ex- views. 
cept the midrib. They are 
gregarious and move in small groups, devouring the foliage on one 
small branch before migrating to another. The cocoons are spun in 
the duff and topsoil beneath the trees. The winter is passed as pre- 
pupal larvae in the cocoons, transforming to the pupal and then to 
the adult stage in the spring. Laboratory records indicate that oc- 
casionally there may be a partial second generation late in August and 
in September. The adults are rather strong fliers and apparently can 
find their food plants, even if the trees are widely scattered and grow- 
ing as individuals in a mixed forest or as shade and ornamental trees. 
The full-grown larva of the larch sawfly (Pristiphora erichsonii 
(Htg.)) is about 84 inch long, with the head and thoracic legs black 
and the body dull grayish green above and paler beneath. This spe- 
cies is a serious defoliator of larch in Europe, Asia, and North Amer- 
ica. Entomologists differ as to whether this species is an introduction 
from Europe or a native of America. Packard (323) stated that its 
presence in North America was not definitely recorded until 1882, 
when severe infestations began to attract attention in Maine. In the 
same year, serious outbreaks were recorded in Massachusetts, New 
Hampshire, New York, and eastern Canada. Graham (194) recently 
stated: 
In Minnesota, the first historical record of larch sawfly injury is in the 
year 1909. The ring pictures of old trees, however, show that reduction 
from defoliation has occurred periodically throughout the life of the oldest 
trees. In addition to the recent period of reduced growth thnt started about 
1909, there were at least two other periods of heavy defoliation, one just pre- 
vious to 1880 and another about 1840. Other minor defoliations occurred about 
1855 or 1860, about 1870, and in the late nineties. Whether or not the larch 
sawfly is a native or an introduced pest can only be shown by further and more 
extensive studies. 
The larch sawfly is now widely distributed through the northern 
part of the United States and in Canada. Severe outbreaks have oc- 
curred at irregular intervals in many localities, sometimes completely 
