INSECT INJURIES TO HARDWOOD FOREST TREES. 



325 



all old trees is thickly perforated. This common defect (see fig. 36) 

 is the work of the chestnut timber- worm (Lymexylon sericeum Harr.). 



CHARACTERISTICS OF THE CHESTNUT TIMBER-WORM. 



The chestnut timber-worm is a curious, yellowish-white, slender 

 larva, full-thrown examples of which are about an inch long. It has a 

 hood-like enlargement just back of the head, and the opposite end of 

 the body is armed with a horny, dark-brown, gouge-like segment, with 

 toothed edges. The adult is a dark-brown, elongate, subcylindrical 

 beetle, densely clothed 

 with tine silky hairs. In- 

 dividuals vary from 10 to 

 15 millimeters (0.4 to 0.6 

 inch) in length. 



The habits of this insect 

 are quite similar to those 

 of the oak timber-worm in 

 breeding in the wood of 

 dead and felled trees and 

 infesting wounds in the 

 wood of living ones. It 

 also enters the living trees 

 at the base of dead or bro- 

 ken limbs, and through 

 small or large knot holes 

 in the trunk. Very little 

 is known of the life his- 

 tory except that the adults 

 develop and emerge about 

 the time the chestnut is in 

 bloom. It is probable that 

 the larva lives several 

 j^ears in its burrow before 

 transforming to the adult, 

 which would account in 

 part for the scarcity of the 

 insects in collections. The common occurrence of its work is explained 

 by the fact that the holes in the wood of old trees may represent the 

 work of many generations during two or three centuries. 



METHODS OF PREVENTING LOSSES. 



In addition to clean forest management and other methods of combating 

 the oak timber- worm, which are just as applicable to this pest, it is impor- 

 tant to clean out the old trees and encourage the growth of thrifty } r oung 

 ones, which are less liable to attack, and to cut these for poles or lum- 



rn as they reach a sufficient diameter to be profitably handled. 

 ,_04 2 



FIG. 38. Work of the Columbian timber-beetle: Black holes 

 and "grease spots" in white oak. (Original.) 



