winter. Trees dead for only a short time and containing considerable amounts of 
moisture are preferred by the larvae. They feed entirely beneath the bark, excavat- 
ing irregular galleries and packing them with fibrous frass. When they become full 
grown they construct oval, fibrous-edged cells in which they pupate and spend the 
winter as adults. 
The old house borer, Hylotrupes bajulus (L.), is native to the Atlas Mountains 
of northern Africa (/93). It was introduced into North America more than a century 
ago. Serious infestations have occurred in the Atlantic and Gulf Coast States from 
Massachusetts to Texas. Spot infestations have been found as far north as Wisconsin 
and Minnesota and as far west as Nebraska. It breeds in dry, seasoned, coniferous 
sapwood. Pine and spruce appear to be preferred, but hemlock, true fir, and 
Douglas-fir are also attacked. The adult (fig. 145A) is a slightly flattened, 
brownish-black beetle from 8 to 20 mm long. The head and forward part of the 
body are clothed with gray hairs; the thorax has several small tubercles at the side 
and a black line and two black spots on the disk; and each wing cover bears either 
patches of gray that fuse to form two crossbands, or two whitish spots. Full-grown 
larvae are wedge shaped, deeply segmented, and up to 30 mm long. 
F-494430, 494432 
Figure 145.—The old house borer, Hy/otrupes bajulus: 
A, adults; B, damage. 
Eggs are deposited in fan-shaped clusters or in rows and layers in holes or tight 
crevices. Stacked lumber and cracks and natural checks in the wood of houses are 
especially subject to attack. Young larvae feed near the surface of the wood; older 
ones bore into the sapwood and seriously damage it with their frass-packed tunnels. 
The larvae seldom break through the surface of the wood. Thus, timbers so severely 
damaged as to be near collapse may appear from the outside to be perfectly sound. 
The length of the life cycle is not exactly known. In the Southern States, from 3 to 5 
years may be required. In the northern parts of its range, an additional 2 to 3 years 
may be necessary. The length of the cycle may also vary considerably in a given 
building. In attics, where generally warmer temperatures prevail, adults may 
emerge up to 2 years earlier than those in wood in the basement. 
The old house borer causes severe damage in houses and other buildings. 
Structural timbers (fig. 145B), framing members, and other wood parts are se- 
riously weakened by larval mining and tunneling. Air-dried pine floor joists, plates 
or sills, and subflooring are apt to be damaged most severely. Other framing such as 
studs, stair carriages, furring strips, and roof rafters are sometimes attacked. 
316 
