F-532334, F-532335 
Figure 172.—Two examples of damage from tunnels of 
the ambrosia beetle, Trypodendron scabricollis, in 
loblolly pine. 
America but it has been found in northern Minnesota and eastern Canada (1/356). 
The genus Gnathotrichus contains several species of true ambrosia beetles (//7). 
The adults are small, cylindrical, and dark brown or black. The head is invisible 
from above, and the body surface is finely punctured, smooth, and sparsely covered 
with hairs near the elytral declivity. 
Gnathotrichus materiarius (Fitch) occurs from eastern Canada south to Florida 
and westward to South Dakota and eastern Texas. It breeds in the lower portions of 
the trunks of dead and dying pines, spruce, balsam fir, larch, and perhaps other 
conifers. Adults are dark brown and about 1.7 to 3.1 mm long. The elytra are 
glabrous except for the declivity and sides which have short, sparse hairs. The 
declivity of the elytra is grooved at the suture. 
Adults bore directly into the wood and their main galleries may have several 
branches (fig. 173). Larval cradles are extended both upward and downward from 
these galleries, and run parallel to the grain of the wood. Pines killed by /ps bark 
beetles in the South are often attacked by this species (76). 
The genus Xyleborus is represented by 19 native and introduced species in the 
Eastern United States (752, 1356). All species are ambrosia beetles. Many breed in 
both conifers and deciduous trees and shrubs of all sizes. Dying, unhealthy, felled, 
or weakened trees or wounds and dead areas in living trees are preferred for attack. 
Males are very rare, quite different from females, and flightless. 
342 
