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AMERICAN FORESTRY 



MMne cases it eats voraciously and continues the destruc- 

 tive work of the larva. 



The hemlock bark beetle (Fig. i), one of the bark- 

 boring insects, is the cause of a large amount of damage 

 to the tree from which it derives its name. The caterpil- 

 lar is a white grub with a large flat head and when full 

 grown reaches a length of nearly an inch. The larva 

 works just under the bark forming irregularly meander- 



FIGURE S. HICKORY BRANCH WITH BARK PARTIALLY 

 REMOVED SHOWING EGG GALLERIES AND CHANNELS MADE 

 BY THE CATERPILLARS OF THE BARK BEETLE. DRAWING 

 OF YOUNO CATERPILLAR MUCH ENLARGED 



ing channels or burrows about a quarter of an inch in 

 diameter and from a few inches to a foot in length. 

 When the work of the insect is completed these burrows 

 are filled with macerated wood resembling fine sawdust 

 and if enough insects are present to girdle its trunk, the 

 entire tree dies. The adult of the hemlock borer is a 

 glistening bronze colored beetle about a half inch long 

 and emerges from its hiding place in the spring through 

 a hole in the bark. The only practical artificial remedy 

 for this insect is the cutting of the infested trees to pre- 

 vent the spread of the pest to those still uninfested. 

 After cutting the trees the wood should be burned, or 

 at least the bark removed and burned in order to prevent 

 the cut trees from serving as sources of infection. This 

 should be done during the winter and the bark disposed 

 of before time for the adults to emerge in the spring 

 of the year. 



The red cedar bark -borer (Fig. 2), an insect similar to 

 the preceding, works in the red cedar giving rise to 

 the characteristic sculpturing which is often evident on 

 red cedar which has been used for rustic work after the 



bark has weathered away. Although the red cedar 

 borer is thought to attack dead or weak trees exclusively, 

 it seems likely, from our own observations, that this 

 insect is responsible to some extent at least for the dying 

 of this tree on estates and in our city parks. As with 

 the hemlock borer, rustic work may serve as a source of 

 infection for living trees unless the bark is removed and 

 the insects prevented from maturing. 



The hickory bark beetle (Figs. 3, 4) is one of the 

 most destructive of all of the bark-boring insects and one 

 which has received a great deal of attention in the last 

 few years. The first evidence of the presence of this 

 pest is the premature dying and falling of the leaves of 

 the hickory in midsummer, about July or August. In- 

 quiries as to the cause of this premature defoliation of 

 the hickories are frequently received. The leaves may 

 fall to the ground or they may be only partially detached 

 and remain hanging in a dead condition, greatly in- 

 juring the appearance of the tree. If the fallen leaves 

 are closelv examined, a small cavitv will be seen at the 



FIGURE 4. HICKORY BRANCH SHOWING HOLES THROUGH 



WHICH THE BARK BEETLES HAVE EMERGED, ABOUT 



NATURAL SIZE. THE DRAWING OF THE BEETLE ITSELF IS 

 ENLARGED 



base of the petiole. These cavities have been made by 

 the adult of the hickory bark beetle which feeds upon the 

 tender tissues at the base of the leaf so weakening the stem 

 that the leaf is easily broken from the tree by the wind or 

 partially detached as described above. If this insect would 

 confine its attacks to the leaves and small twigs the injury 

 would be comparatively slight, but unfortunately, they 

 also attack the large branches or main trunk of the tree and 

 it is here that the principal part of the damage is done. 



