INSECT ENEMIES OF WESTERN FORESTS 179 



lay eggs in bark crevices or in mechanical wounds on the trees. 

 The larvae start the construction of mines from the place where 

 the eggs are laid and bore winding mines through the inner bark 

 and the outer layers of wood. A large mass of gummy, sticky 

 pitch, mixed with boring dust, exudes from the point of entrance. 

 Two years are required to complete the life cycle, and the larvae 

 pass both winters in their galleries. When mature the larvae trans- 

 form to pupae within the pitch mass, and just prior to emergence 

 the pupae push their way partially out, to permit the moths to 

 emerge without coming in contact with the pitch mass. 



The Douglas-fir pitch moth (Vespamima novaroensis (Hy. 

 Edw.)) is a shining black species with a red spot on the under 

 side of the abdomen. The caterpillars attack wounds on Douglas- 

 fir throughout the range of this tree and have also been recorded 

 from weakened larch and Sitka spruce. Like the sequoia pitch 

 moth, the economic importance of this moth lies primarily in the 

 subsequent lumber defects (16). 



The adults are clear-winged moths with a wing expanse of 1% 

 inches. They have spots of orange red on the thorax and bands of 

 the same color on all the body segments except the last. The males 

 are distinctly smaller than the females. The larvae are slender 

 white caterpillars with brown heads, and when full grown range 

 in length from 1 to iy 2 inches. The larval skin is transparent, and 

 in this respect the larvae differ from those of the sequoia pitch 

 moth. 



Brunner reports the appearance of the adults during the latter 

 part of May and in June. The habits are comparable to those of 

 the sequoia pitch moth, except that 4 years are required for de- 

 velopment. Winters are passed by the larvae in their galleries, 

 which are covered with large accumulations of pitch. 



Some species of the family Pyralidae, or snout moths, work in 

 the inner bark of various coniferous trees, causing a heavy exuda- 

 tion of pitch, and cause injury very similar to that of the clear- 

 winged moths. Most of these do more serious damage to young 

 trees than to older ones and therefore were discussed in the section 

 dealing with young trees (p. 32). 



INSECTS INJURIOUS TO WOOD AND 

 OTHER FOREST PRODUCTS 



Insects take a heavy toll of crude and finished forest products 

 (38, 73, 137, lJf5). This loss has been variously estimated at 1 

 to 5 percent of the annual cut. The principal damage to forest 

 products is caused by insects that feed on or bore into the wood. 

 A great deal of this damage occurs after trees have been killed 

 or felled, and before utilization. Green or seasoned lumber and 

 even the final utilized products are fed on by insects. 



