ing upward and downward from the tunnels (20/). Both species are highly destruc- 
tive of green lumber and fresh logs of gum in the Gulf States. 
Xyloterinus politus (Say), a widely distributed species in eastern North America, 
breeds in injured, dying, and recently cut trees and limbs of a variety of trees such 
as beech, birch, hard and soft maples, hickory, oak, ash, magnolia, black cherry, 
red spruce, pine, and hemlock. It is rare in coniferous hosts. The adult is dark 
brown to black and about 2.7 to 3.7 mm long. The pronotum is almost square, 
rugose in front, and has the anterior margin armed with four teeth. The galleries of 
this species differ from those of many other ambrosia beetles in that they often fork 
and branch secondarily, and they also possess four rows of larval cradles, two above 
and two below the gallery (800, SO/). Lumber cut from infested wood may be 
severely degraded by adult entrance holes and by associated stains. 
Five species of the genus Trypodendron occur in eastern North America. Adults 
are distinguished by having completely divided eyes and by the absence of distinct 
sutures in the antennal club. The frons of the male is broadly excavated; that of the 
female is convex. The oral region of the head is visible from above. The gallery 
penetrates the sapwood and branches one or more times. The larvae are reared in 
cradles extending upward and downward from the tunnels. The cradles are enlarged 
by the larvae and serve as pupation chambers (/356). 
The striped ambrosia beetle, 7. lineatum (Olivier), occurs over much of 
Canada, and the Western and Northeastern United States. It also occurs in the 
mountains of western North Carolina. It breeds in a wide variety of conifers and 
occurs rarely in hardwoods. The adult is from 2.7 to 3.5 mm long. They are dark 
brown to black, with each elytron usually marked with two light yellowish-brown 
stripes parallel to the suture. These stripes extend to the base of the pronotum. The 
main gallery of the species extends straight into the wood for 2.5 to 5 cm and then 
divides into two or more branches. Larval cradles are situated at the upper and lower 
surfaces of these branches. Damage to felled timber, and to damaged, injured, or 
fire-scorched trees is often severe. 
Trypodendron scabricollis (LeConte) occurs from Minnesota and Arkansas east- 
ward, and breeds in various species of pine and hemlock. The trunks (fig. 172) and 
larger limbs of weakened and dying pines are preferred, but freshly cut lumber is 
also subject to attack and serious damage. Adults are from 3.5 to 4.1 mm long, and 
brown with a faint, light stripe extending from the basal one-fourth of the pronotum 
down each elytron. The elytra are smooth and finely striate. The gallery system has 
an entrance tunnel extending 2.5 to 5.0 cm into the wood. The gallery branches left 
and right, following an annual ring. Larval cradles extend above and below these 
secondary tunnels (76). 
Trypodendron retusum (LeConte), the largest of the eastern species, attacks 
poplars across the Northern United States and southern Canada. It has also been 
recorded from West Virginia and several Western States from Alaska to Arizona. 
Adults are 3.6 to 4.6 mm long and uniformly black when fully mature except for 
pale yellowish-brown areas at the base of the pronotum and on the elytra from the 
base to the declivital margin continuing on the sides of the declivity to the apex. T. 
betulae Swaine occurs throughout the Northern States and across Canada, and 
breeds in unthrifty standing birch. Adults are dark brown to black and from 2.7 to 
3.5 mm long. There is a faint yellowish-brown area of variable size on each elytron 
from the base to the declivital margin (/356). 
Trypodendron rufitarsis (Kirby) attacks injured or dying pines and spruces, 
evidently preferring standing trees over logs. It occurs over much of western North 
371 
