INSECT ENEMIES OF WESTERN FORESTS QO] 
The Monterey pine sawfly (/tycorsia sp.) attacks only the Monterey 
pine in its native habitat, near Pacific Grove, Calif. The larvae are so 
prevalent at times as to completely defoliate the trees, either killing 
or seriously weakening large numbers of them. The larvae are dark 
green or brownish, with black heads. A characteristic of their work 
is that the needles are sawed off or chewed into a mass, and these 
broken needles and brownish excrement pellets are webbed together 
with silken threads. | 
The hemlock sawfly (Weodiprion tsugae Midd.) occasionally be- 
comes epidemic and defoliates extensive areas of western hemlock 
in Oregon and northward into Alaska. The adults are small, about 
one-fourth inch in length. The males are dark brown to black, and 
the females are larger and green to yellowish brown. The larvae 
are green and about 1 inch in length when full grown. The papery 
cocoons are attached to the needles and to debris on the ground. 
In the northwestern part of the United States there are two species 
of sawflies that feed on the foliage of western larch. So far they 
have not caused damage of any great economic importance. In 1921 
an outbreak of these two insects occurred throughout the larch stands 
of northern Idaho and western Montana. This is the first and last 
record of their appearance, and although they occurred in countless 
numbers in 1921, it was practically impossible to find a single larva 
in 1922. This isa marked example of how rapidly an outbreak can 
disappear. 
The larvae did their heaviest feeding from the middle of July to 
the last of August, and either devoured the foliage or killed it by 
chewing on the fleshy portion of the needles anywhere between the 
tip and base. ‘The larvae leave the trees when they are mature 
and spin small silken cocoons under the duff, in which they pupate. 
Small pebbles and grains of sand adhere to these cocoons, giving 
them the appearance of small lumps of dirt. The winter is passed 
in the cocoon, and the new adults emerge the following spring about 
the time the larch foliage appears. 
Adults of the two-lined larch sawfly (Platycampus laricis Roh. and 
Midd.) are small, black, wasplike insects, a little less than one- 
fourth inch in length. The folded wings have a blue-green metallic 
sheen. The larvae are rather slender, about three-eighths inch in 
length when full grown, with eight pairs of prolegs on the abdomen 
and are brownish-green with two narrow dark-green stripes along 
the sides, dark-brown heads, and black, shiny eyes. The western 
larch sawfly (Platycampus laricivorus Roh. and Midd.) closely re- 
sembles the foregoing in the adult stage, but the larvae have a single 
green line down the center of the back. 
The larch sawfly (Nematus (Lygaeonematus) erichsonii Hartig) 
which is a native of Europe and was first found in New England 
about 1880, has spread westward through the Lake States and Canada 
into northern British Columbia. Its progress has been disastrous 
imasmuch as it kills trees rapidly, and has left vast areas of dead 
and dying larch in its wake. Only recently it has been reported at- 
tacking western larch in southern British Columbia and in the north- 
western part of the United States. 
The cypress sawfly (Susana cupressi Roh. and Midd.) feeds on 
the foliage of Monterey cypress in California. 
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