INSECT ENEMIES OF WESTERN FOKESTS 29 



width, free from packed boring dust, made by 

 small brown beetles; and larval tunnels packed 

 with fine borings made by small, white, curled, 



legless larvae twig beetles, page 30. 



6. 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. 



c. 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 

 heads twig borers, page 8.5. 



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. Succulent tips covered with small, soft-bodied insects, 

 or stems covered with powdery, cottony incrusta- 

 tions or shell-like scales ; trees dripping a sticky 

 exudation ; often covered with a black smut 



sap-sucking insects, page 44. 

 6. Terminal shoots or leaves enlarged, galled, or swollen 



gall makers, page 52. 

 c. 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 



larger branches 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, sucli 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- 



