INSPECT KNEMIES OF WESTERN FORESTS ()\ 



The Monterey pine sawfly (Itycorsiasp.) 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 serionsly weakenino- laroe numbei'S of them. The larvae arc dark 

 ^reen or brownish, with black heads. A characteristic of their work 

 is that the needles are sawed off or chew^ed into a mass, and these 

 broken needles and brownish excrement pellets are webbed together 

 with silken threads. 



The hemlock sawfly {Neodiprion tsugae Midd.) occasionally be- 

 comes epidemic and defoliates extensive areas of western hemlock 

 in Oregon and northw^ard 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 is a 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 {Platycam^pus 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 {Neinatus {LygaeoneTuatus) 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 

 inasmuch 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. 



