aa 
Courtesy Duke Univ. Sch. For. 
Figure 140.—Adult of the tilehorned 
prionus, Prionus imbricornis. 
the Eastern United States. Adults are light brown, shiny, and 25 to 45 mm long. The 
elytra are densely punctured. 
Several species of Xylotrechus occur in eastern forests. Adults are characterized 
by their moderate size, their short, filiform antennae, and a V-shaped callosity on 
the front of the head. 
Xylotrechus quadrimaculatus (Haldeman), the birch and beech girdler, breeds 
in the branches of birch, beech, American hornbeam, maple, and alder in eastern 
Canada and Northeastern United States. Adults are 7.5 to 14 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 5 cm in diameter frequently fall to the ground during midsummer 
with the larvae in them. There is one generation per year. 
The gallmaking maple borer, X. aceris Fisher, breeds in the trunks and 
branches of various maples, especially small red maples, causing the formation of 
galls. The adults resemble those of the birch and beech girdler, although they have 
fainter spots on the thorax and stronger markings on the elytra. The adults are 10 to 
14 mm long. Eggs are deposited during midsummer 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 
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