INSECT ENEMIES OF EASTERN FORESTS 293 
The species of the genus Rhyncolus are similar to those of Cossonus, 
but smaller and more cylindrical. &. bruwnneus Mann., which is dark 
red, is common in dying coniferous wood. A closely related, dark- 
brown species, Zexarthrum ulkei Horn, is found in manufactured coni- 
ferous wood products in the eastern part of the United States. This 
species is sometimes destructive to the woodwork of old buildings and 
occasionally reduces the wood to powder, necessitating the removal of 
much material. This beetle is often associated in wood infested with 
the anobud Ayletinus peltatus (Harr.). Another black, shining 
species, Zomolips quercicola Boh., also has been found causing damage 
in buildings to seasoned coniferous woods such as pine floorings and 
pecky cyprus paneling. Pselactus spadix (Ubst.) has been taken from 
salt water piling just above the high-water mark in railroad piers at 
East Boston, Mass. Occasionally it is found in the damp woodwork 
beneath buildings. Dryophthorus americanus Bedel has been reported 
from both hardwoods and softwoods, and is very common in hickory 
killed by the hickory bark beetle. Stenoscelis brevis (Boh.) is very 
common in dead, dying, and rotten hardwoods. 
The larvae of all the species cut meandering galleries across the 
grain of the wood and pack them tightly with granular frass except 
for that portion immediately behind them. The adults may be found 
in the wood, or, more usually under the bark about a year after the 
tree is killed. The subfamily is not very important economically, ex- 
cept for the occasional attack on wood utilized in buildings and the 
fact that the galleries frequently interfere with the utilization of the 
sapwood of trees killed by bark beetles. 
Famity SCOLYTIDAE 
THE BARK BEETLES 
By M. W. BLacKMAN 
The bark beetles (Scolytidae) are small cylindrical beetles ranging 
from less than 2 mm. to about 9 mm. in length. Mature specimens 
range from brown or reddish brown to black, depending on the species. 
A few species are marked with contrasting colors, which may be due 
either to actual color differences in the body wall or elytra, as in certain 
species of 7rypodendron and Monarthrum, or may be produced by the 
grouping of scales or setae of different colors, as in Leperisinus and 
Pseudohylesinus. The individuals of most species, however, are 
usually more or less uniform in color. 
Technically, the Scolytidae belong to the suborder Rhynchophora 
of the order Coleoptera, as they possess undivided maxillae and rigid 
palpi of not more than three joints, and the larvae are legless. They 
differ, however, from the Curculionoidea and other Rhynchophor a in 
that the head is never produced into a prominent rostrum or snout and 
the submentum lacks a gular peduncle. The characteristic elbowed 
antennae serve to distineuish them readily from the Bostrichidae, 
some forms of which bear a superficially strong resemblance to bark 
beetles. In all but a few species the antenna has a compact club. 
The larvae are small, soft, white or yellowish-white, legless grubs, 
usually strongly curved and dorsally plicate with a prominent and 
strongly sclerotized head. They have triangular mandibles of the 
