INSECT ENEMIES OF WESTERN FORESTS 29 
width, free from packed boring dust, made by 
small brown beetles; and larval tunnels packed 
with fine borings made by small, white, curled, 
leclessularvaes eee eee a twig beetles, page 30. 
b. Point of attack not conspicuous and not showing a 
small pitch exudation. Tunnels under bark, nearly 
round, free from pitchy exudations, filled with 
coarse or powdery boring dust. Made by small, 
white, curled, legless grubs__----- twig weevils, page 33. 
ec. Point of attack not conspicuous. Tunnels under bark 
broadly oval or nearly flat and filled with boring 
dust. Made by slender white grubs with broad 
NEED CS at Rea OT RE es twig borers, page 25. 
d. Bark and wood of twigs conspicuously gnawed and 
girdled, causing death and breakage 
twig girdlers, page 35. 
e. Point of attack showing resinous exudation, with lar- 
val castings webbed together, or pitch nodule. 
Resinous tunnels under bark or in the shoots 
made by active caterpillars 
twig moths or tip moths, page 37. 
2, Leaves and buds at tips of branches webbed together and 
killed. Very little damage to other parts of the shoots 
bud moths, page 44. 
3. Tips of branches appearing unhealthy, sickly, badly swollen 
and deformed, or killed. No borings under the bark. 
a. Sueculent tips covered with small, soft-bodied insects, 
or stems covered with powdery, cottony incrusta- 
tions or shell-like seales; trees dripping a sticky 
exudation ; often covered with a black smut 
sap-sucking insects, page 44. 
b. Terminal shoots or leaves enlarged, galled, or swollen 
gall makers, page 52. 
ce. Twigs with dying and dead needle tufts, bark filled 
with resinous pockets containing small red maggots 
pitch midges, page 54. 
B. Entire tree, or a large part, sickly, dying, or dead; foliage fading, turn- 
ing yellow or red. 
1. Tunnels or borings found under the bark of the main trunk or 
ANGE OTA CHIC Sosa eas ae cambium feeders, page 56. 
2. Insects found feeding on the roots___-________ root feeders, page 24. 
3. Foliage fed upon, partially or wholly stripped from the trees, 
or appearing sparse and sickly_____________ defoliators, page 56. 
INSECTS AFFECTING TWIGS, TERMINAL SHOOTS, AND BUDS 
Injury to leaf buds, succulent terminal shoots, and growing tips 
may be caused by insects of a number of different groups, such as 
twig-boring caterpillars, twig weevils, twig beetles, roundheaded or 
flatheaded borers, or even pitch midges, aphids, and ‘scale insects (fig. 
11). Such insects show a decided preference for these tender, grow- 
ing parts of the trees. The damage they do to the new growth of 
older trees is of much less importance than that done to young trees 
in the formative stage. In the normal forest the damage of this 
character to native trees is rarely extensive enough to be of serious 
consequence, but on cut-over lands and in plantations it is frequently 
disastrous. 
The seriousness of this type of damage is shown in the sand-hill 
plantations of the Nebraska National Forest. Two species of pine 
tip moths (Rhyacionia spp.), which were of little importance in their 
native habitat, found their way into these new isolated plantations. 
In the new environment, freed from their native parasites and find- 
apse 
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