The rustic borer, X. colonus (F.), one of the most common of all cerambycids in 
the Eastern United States, feeds under the bark of almost all dead hardwoods. It 
occurs also in southern Canada. The adult (fig. 142) is light to dark brown and 8 to 
15 mm long. Each elytron is marked with an irregular line of fine yellow hairs back 
of the base and three transverse bands of gray hairs—one band just behind the 
yellow line at the base, one back of the middle, and one at the apex. The larvae feed 
almost exclusively in the bark without scarring the wood (463). Recently killed 
trees are preferred. 
Courtesy Duke Univ. Sch. For. 
Figure 142.—Adult of the rustic borer, 
Xylotrechus colonus. 
Xylotrechus annosus annosus (Say) breeds in poplar and willow in eastern and 
central Canada and in the Northeastern and Lake States. X. undulatus (Say) breeds 
in recently cut spruce, Douglas-fir, and lodgepole pine from eastern Canada and the 
Lake States to Yukon Territory and central Alaska. 
The genus Monochamus is represented by several important wood-boring species 
in eastern forests, all of which breed in various conifers. The larvae are commonly 
known as “‘sawyers” because of the loud noise they make while feeding. Freshly 
cut, feiled, dying or recently dead trees are preferred. Young larvae feed on the 
inner bark, cambium, and outer sapwood, forming shallow excavations called 
surface galleries which they fill with coarse, fibrous borings and frass. As they 
grow older, they bore deep into the heartwood, and then turn around and bore back 
toward the surface, thereby forming a characteristic U-shaped tunnel. A pupal cell 
is formed at the outer end of the tunnel. from which the adult emerges by chewing a 
hole out through the remaining wood and bark. Full-grown larvae are often more 
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