INSECT INJURIES TO HARDWOOD FOREST TREES. 



323 



INSECT INJURIES TO THE AVOOD OF LIVING TREES. 



The class of injuries to the wood of living trees known as pinholes 

 and wormholes cause an enormous loss of the best hardwood timber. 

 Indeed the loss from this cause is perhaps far greater in the aggregate 

 than that resulting from the work of the bark-borers alread\ T men- 

 tioned. Trees dying or dead from the work of bark-borers are con- 

 spicuous and thus attract attention, while that of the wood-borers is 

 obscure and seldom noticed until the trees are closely examined or 

 felled. Indeed, hundreds of generations of one of this class of enemies 

 may breed in and emerge from a tree during its life, and the heartwood 

 of the trunk be rendered worthless for commercial purposes, yet the 

 tree may continue to live and grow and show little or no outward 

 indication of damage. 



PINHOLE INJURIES IN OAK AVooo. 



One of the most destructive of this class of enemies of hardwood 

 forest trees is the oak timber-worm (Eupsalis minuta). This is a 



slender whitish worm, or grub, full-grown 



examples of which are less than an inch long 

 and one-sixteenth of an inch or less in 

 diameter toward the middle of the body, 

 while the segments toward the head are 

 enlarged to twice this diameter. The adult 

 is a slender reddish snout-beetle, with black 

 markings, varying in length from 10 to 15 

 millimeters (0.4 to 0.6 inch). The beetles 

 appear on the wing in April and May, and 

 are found through the spring and summer 

 months on or about fresh or old wounds on 

 living trees. They deposit their eggs in the 

 surface and edges of these wounds, and the 

 minute young larvae bore, at first, almost 

 invisible holes directly into the wood. 

 These burrows are enlarged and extended 

 in all directions through the heartwood until 

 the larvae have attained their full growth. 

 They then transform to adults within their 

 burrows, to emerge the next spring or summer and repeat the process in 

 the same wounds, or in the wood of dead standing trees and the stumps 

 and logs of felled ones. Thus, an ax wound in the side of a large, 

 sound, and healthy tree may result in an attack by this insect, and in 

 a few years the entire keartwood of 3 or 4 feet of the trunk is perfo- 

 rated with the so-called pinhole defects (fig. 35). Slight wounds by light- 

 ning may, in a like manner, result in the wood of the entire trunk 



ing thus rendered worthless for stave timber or first-class lumber. 



FIG. 35. Pinholes in oak work 

 of the oak timber - worm. 

 (Adapted from author's illus- 

 tration.) 



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