8 MISC. PUBLICATION 273, U. 8. DEPT. OF AGRICULTURE 
Bud and twig moths, tip weevils, and twig beetles not only damage 
and deform the terminal shoots but at times become so numerous as 
to kill out seedlings, saplings, and poles over large areas. Pine 
plantations in the Nebraska sand hills have been badly set back by tip 
moths. Many areas of second-growth pine near logging operations 
have been swept by aggressive infestations of engraver beetles. 
The destruction of trees especially valuable from a recreational or 
aesthetic standpoint has recently come into prominence because of 
rapid progress in the development of forest recreation. The impor- 
tance of forest cover on national parks, game preserves, and other 
recreational areas cannot be estimated in board-feet values. Insect 
depredations which mar the beauty or destroy the protective value 
of the forest cover on park and other recreational areas justify higher 
expenditures for suppression than might be reasonable on a strictly 
commercial stand. 
Injuries to the wood of living trees are manifested in lumber as 
defects greatly reducing its value. Furthermore, all kinds of forest 
products, from the time the tree is felled and for many years after 
the wood is put into use, are subject to destruction by insects. Green 
sawlogs and storm-felled timber, green sawed lumber and seasoned 
lumber, rustic construction, poles, posts, cross ties, and all manner 
of finished products, from flooring to furniture, are attacked. Losses 
in finished products are particularly heavy, since they include cost 
of manufacture or replacement, or both. Losses of this class, it 1s 
estimated, amount to from 0.5 to 5 percent of the total value of vari- 
ous classes of finished products. 
INDIRECT LOSSES 
Besides direct damage through destruction of trees and forest 
products, forest-tree insects cause important indirect losses in the 
way of reduction in forest growth and alteration of the stand from 
valuable to inferior species. 
In some forest types insects often are one of the chief limiting 
factors in successful management. They frequently upset well-or- 
ganized plans aimed at the continuous production of forest crops. 
In the western white pine and lodgepole pine forests of the northern 
Rocky Mountain region bark beetles so affect the proportion of 
species as to convert many stands to entirely different composition. 
In Modoe County, Calif., a bark-beetle epidemic in a mixed second- 
growth stand of ponderosa pine and white fir killed out all the pine 
and converted the stand into pure fir. 
Much less frequently the effect of insect activity on stand compo- 
sition is beneficial. In the Yosemite and Crater Lake National Parks, 
for instance, lodgepole pine stands completely destroyed by bark 
beetles have been succeeded by stands of the hemlock-fir type, which, 
for park purposes at least, is far superior to the lodgepole pine type. 
Certain defoliators, even though they do not kill the timber, may 
cause a cessation or reduction of growth which may increase the ro- 
tation period of the stand by from 5 to 10 or more years, or they 
may so weaken the trees as to make them easy prey for tree-killing 
bark beetles. Such defoliation may be local and confined to a single 
tree species. or may spread over an enormous area and involve sev- 
