INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 61 



more or less affected, and a large percentage is so seriously damaged 

 that the product is reduced to that of the lowest grade. " It is esti- 

 mated that the reduction in value of the average lumber product at 

 any given time is not far from 30 per cent, thus involving extensive 

 waste and an increased drain on the forest to supply the require- 

 ments for clear lumber. This insect also attacks the oaks, and 

 especially the red oak, the older trees of which are often as seri- 

 ously damaged as are the chestnut. (Hopkins, 1894a, 19046.) 



Carpenter icorms.—Th.% oaks, especially the white oak and the red 

 oak, are seriously damaged by carpenter worms of the genus Prion- 

 oxystus. The holes made by these insects through the heartwood of 

 the best part of the trunks are sometimes 1.5 inches in diameter one 

 way by 0.75 inch the other, thus causing serious damage to the wood. 

 These, with other large wood-boring beetle larvaa, sometimes infest 

 the top part of the trunk and the larger branches of oak trees, where 

 their continued work results first in the dead and so-called " stag- 

 horn " top and subsequently in broken, decayed, and worthless 

 trunks. (Hopkins, 1894a, 19046.) 



Ambrosia beetles. — One of the commonest defects in white oak, rock 

 oak, beech, whitewood or yellow poplar, elm, etc., is that known to the 

 lumber trade as " grease spots," " patch worm," and " black holes." 

 This defect is caused by one of the timber beetles or ambrosia beetles, 

 Corthylus coliimbianus Hopk., which makes successive attacks in the 

 living healthy sapwood from the time the trees are 20 or 30 years 

 old until they reach the maximum age. Thus the black-hole and 

 stained-wood defect is scattered all through the wood of the best 

 part of the trunks of the trees. The average reduction in value 

 of otherwise best-grade lumber amounts, in many localities, to from 

 25 to 75 per cent. The defect is commonly found in oak and elm 

 furniture and in interior hardwood finish in dwellings and other 

 buildings. (Hopkins, 1893y, 1894&, 1904&.) 



The locust borer. — The locust, as is well known, suffers to such an 

 extent from the ravages of the locust borer {Cyllene robinim Forst.) 

 that in many localities the trees are rendered worthless for commercial 

 purposes or they are reduced in value below the point of profitable 

 growth as a forest tree, otherwise this would be one of the most profit- 

 able trees in the natural forest or artificial plantation and would con- 

 tribute greatly to an increased timber supply. (Hopkins, 1906Z>, 

 1907a, 1907c.) 



Turpentine beetles and turpentine borers. — While the softwood 

 trees, or conifers, suffer far less than the hardwoods from the class 

 of enemies which cause defects in the living timber there are a 

 few notable examples of serious damage. There is a common trouble 

 affecting the various species of pine throughout the country known 

 as basal wounds or basal fire wounds. It has been found that a large 



