Courtesy Duke Univ. Sch. For. 
Figure 173.—Tunnels of the ambrosia beetle, 
Gnathotrichus materiarius, in the wood of a shortleaf 
pine. 
Xyleborus celsus Eichhoff, the largest member of the genus occurring in the 
United States, breeds in dead, dying, and recently felled trees and stumps of 
hickory in the Eastern United States west to lowa and Texas. Females are reddish 
brown and about 3.6 to 4.5 mm long. The declivity of the female is steep, almost 
flat. The sides and upper margin of the declivity are armed with several acute 
tubercles, and the area between the suture and first stria is broad, smooth, and 
armed with two large teeth. The galleries of this species extend directly into the 
wood for | to 3 cm or more, then branch one to six times in a fan shape. Eggs are 
laid near the ends of the galleries. There are two generations per year in southern 
Missouri (459). Hickories killed by the hickory bark beetle are especially subject to 
attack in the Southeast (76). 
Xyleborus dispar (F.) is widely distributed in southern Canada and the Eastern 
States south to North Carolina. It attacks all the common fruit trees as well as a 
great many other hardwood trees. It has also been reported from pine and hemlock. 
Females are black and 2.8 to 3.5 mm long. In large trunks, the galleries extend 
straight into the wood from | to 3 cm and branch on the same plane following an 
annual ring. In small trunks and branches, the galleries spiral upward from the 
point of attack around the stem or limb, branching upward or downward from the 
spiral gallery (20/). 
Xyleborus ferrugineus (F.) occurs from Massachusetts and Michigan south to 
Florida and Texas. It breeds in dead, dying, or felled trees of a wide range of 
species including oak, hickory, ash, baldcypress, walnut, pine, beech, and sweet- 
gum. Females are reddish brown and from 2 to 3.3 mm long. The elytral declivity 
of the female is flat. The third interspace of the declivity is armed with one to three 
acute granules on the basal half and one coarse denticle at the middle; the fourth 
and fifth interspaces are armed with two to four granules each. Galleries resemble 
those formed by X. ce/sus except that they are smaller in diameter; they also may be 
longer and more winding and branch less frequently in the same plane. Side 
branches are formed which lead to other sets of galleries at different levels. The 
galleries may penetrate all of the sapwood but they are less common in the 
heartwood. X. ferrugineus may form shallow galleries that are visible on the surface 
of the wood when the bark is peeled (/356). 
373 
