INSECT ENEMIES OF WESTERN FORESTS 



59 



Figure 23.- 



-Old vacated gall of the Gooley spruce gall aphid (Chermes 

 cooleyi) on blue spruce. 



in the galls become full-grown, winged migrants, which return 

 to the Douglas-fir to lay eggs that also produce hibernating fe- 

 males. Altogether there are five stages or forms in which Chermes 

 appear during different periods of their development. 



The species is distributed from British Columbia to California 

 and eastward into Idaho, Montana, Wyoming, and Colorado. 



Chermes oregonensis Annand appears as a small woolly louse on 

 the twigs and base of larch needles in Oregon, Washington, and 

 Montana, but does little damage. 



The balsam woolly aphid (Chermes piceae (Ratz.) ) (fig. 24) is 

 a species introduced from northern Europe which has caused 

 extensive damage in the Northeastern States and Canada. It has 

 been reported from the San Francisco Bay area and the Willamette 

 Valley on noble fir and grand fir (1). Since 1930 it has become 

 exceedingly destructive to grand fir in western Oregon. On the 



