COURTESY OF DUKE UNIV. SCH. OF FOREST. 
FIGURE 68.—Adult of the tile- 
horned prionus, Prionus imbri- 
cornis. 
Several species of Xylotrechus Chev. occur in eastern forests. 
Adults are characterized by their moderate size, their short, fili- 
form antennae, and a V-shaped callosity on the front of the head. 
Aylotrechus quadrimaculatus (Hald.), the birch and beech 
girdler, breeds in the branches of birch, beech, blue beech, maple, 
and alder in the Eastern States. Adults are about 12 mm. long. 
The thorax is black with four yellow spots; the wing covers pale 
brown with faint white marks. Eggs are deposited in the axils of 
twigs, in bark crevices, and in healed over injuries on branches. 
Young larvae feed beneath the bark, often girdling and killing 
the branch quickly. Later they bore toward the pith in concentric 
circles until the branch is almost severed. At this point, they turn 
and bore toward the tip, packing their tunnels with granular 
frass. Before reaching the tip they construct pupal cells in which 
they spend the winter and in which they pupate in the spring. 
Damaged branches up to 2 inches in diameter frequently fall to 
the ground, with the larvae in them, during mid-summer. There 
is one generation per year. 
The gall-making maple borer, Xylotrechus aceris Fisher, breeds 
in the trunks and branches of various maples, causing the forma- 
tion of galls. The adults resemble those of the birch and beech 
girdler, although they are somewhat smaller and have fainter 
spots on the thorax and stronger markings on the elytra. Eggs 
are deposited during mid-summer in wounds or at the bases of 
small dead twigs along the trunk. The larvae bore directly into 
the sapwood. Later they construct tunnels in the heartwood, often 
completely destroying the center of the trees and causing the 
formation of galls or swellings about the wounds. During the 
second summer of their lives, they bore either directly upward or 
downward and pupate in cells at the end of their tunnels. Infested 
trees are never killed outright but are seriously weakened, be- 
coming subject to breakage by the wind. 
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