trees are attacked including spruce, hemlock, Fraser fir, and pine. There have also 
been reports of infestations in yellow-poplar. The adult is from 3.5 to 5 mm long. It 
differs from the adults of all other species in the genus in having a distinctly 
punctured pronotal disk. a convex declivity with the sutural interspace only slightly 
raised, and in the absence of a dense mat of hair on the female frons. 
The birch bark beetle, D. betulae Hopkins, occurs from coast to coast in 
Canada and south to Florida and Mississippi in the Eastern States. Its hosts are 
recorded as birch, beech, sweetgum, cherry, and pear. Attacks are generally 
confined to dead and dying trees, logs, and stumps. The adult female is reddish 
brown, has a dense mat of hairs on the frons, and is from 2.8 to 4.5 mm long. 
Dryocoetes caryi Hopkins occurs throughout the northern coniferous forests and 
south to North Carolina in the Eastern States. Its hosts are white. red. and 
Engelmann spruces. Infestations are usually confined to the trunks of small, 
weakened. shaded-out, suppressed trees. The female adult is reddish brown and 
from 2.1 to 2.7 mm long. 
Dryocoetes granicollis (LeConte), a rather rare species, breeds in spruce from 
Quebec to North Carolina. The female adult is reddish brown and from 2.3 to 3 mm 
long. 
The genus Crypturgus is represented in eastern forests by three common species, 
none of which is economically important. The adults are brown or black, about | 
mm long, and are found in the inner bark of dead or dying conifers. Their short. 
irregular burrows usually originate from the burrows of larger bark beetles, but 
sometimes from ventilation holes made by Monochamus spp. C. alutaceus Sch- 
warz, the smallest of all North American bark beetles, occurs from New Jersey to 
Florida. It breeds in species of pine, and in black and Norway spruces. C. borealis 
Swaine breeds in various conifers from Maine to Pennsylvania. C. pusillus 
(Gyllenhal), a species introduced from Europe, attacks pine, spruce, balsam fir, and 
larch in eastern Canada and from Maine and New York to West Virginia and the 
Lake States. 
The genus Pseudopitvophthorus is closely allied to Pityophthorus, but differs in 
that the adults have a longer and more acute prosternal process (//8). The first 
segment of the antennal club also is longer than those in Pityophthorus, and the 
males rather than the females have long, yellowish hairs on the front of the head. 
The majority of species prefer to breed in the inner bark of recently cut or dying 
limbs of various species of oaks. A few species attack other tree species, and some 
attack and kill perfectly healthy limbs. 
Pseudopityophthorus minutissimus (Zimmermann), the oak bark beetle. a com- 
mon and widely distributed species from Quebec and Massachusetts to Georgia and 
westward to Mississippi and Colorado, breeds in various species of oaks and 
occasionally in many other hardwoods. The adult is dark reddish-brown, from 1.5 
to 1.9 mm long. and can be distinguished from other species in the genus by the 
reticulate frons and pronotal disk in both sexes. In the southern portions of its 
range, it is active throughout the year, and there are at least two generations per year 
as far north as the Lake States. Eggs are laid in circumferential galleries in branches 
from 12 to 100 mm in diameter and the larvae tunnel away from the gallery. 
following the grain of the wood. When the adults emerge. they fly to the tops of the 
trees and feed on the buds, in twig crotches, in the axils of leaves, and in immature 
acorns. Because of these habits and because of the abundance of the species in 
stands suffering from oak wilt disease, this species is strongly suspected of playing 
a primary role in the transmission of the fungus (/68). 
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