330 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Pityogenes hopkinsi is a small reddish-brown beetle about 2 mm. 
long, with the pronotum projectile-shaped, and the elytra armed with 
three teeth at each side, those on the male being larger. The female 
has a circular pit in the front of the head. This beetle is widely dis- 
tributed in eastern Canada, and in the United States extends from 
Maine to Wisconsin and southward to North Carolina. Its distribu- 
tion conforms to that of its favorite host tree, white pine. This insect 
is more abundant in the northern tier of States than farther south. 
Other species of pine and occasionally spruce are also attacked, though 
more sparsely (Blackman, 35). 
Pityogenes lecontet is similar to P. hopkinsi, but the females 
are easily recognized by the frontal pit, which is divided into two 
parts by a median carina. Aside from the type in the Leconte col- 
lection, P. Zeconte? is known from specimens collected in three locali- 
ties in Pennsylvania. PP. plagiatus is similar in size, but the frontal 
pit of the female is replaced by a triangular pubescent area, and in the 
males the dorsal tooth of the elytral declivity is enlarged and hooked 
at the end. It occurs in the Atlantic States and is especially common 
in West Virginia and southern Pennsylvania. Various species of pine 
are attacked by it. P. meridianus is similar in structure but is con- 
siderably longer (2.8 mm. long) and more slender. The front of the 
female lacks both pit and pubescent area, and in the male the declivital 
teeth are similar to those in P. plagiatus but longer and more slender. 
Tt has been taken from shortleaf pine and loblolly pine at five localities 
in Mississippi and is not known from elsewhere (Blackman, 38). 
The genus P7tyoborus Blkm. contains only a single eastern species, 
P. comatus (Blackman, 38). It is readily distinguished from 
Pityophthorus, the most closely related genus, : and from all other North 
American genera by a patch of fine, dense, yellow, silky hair on each 
side of the pr onotum of the female. P. comatus breeds in pine bark, 
preferring the lower branches, which are still alive but weakened from 
being shaded. The insects may be occasicnally injurious, but are most 
often of little economic importance. They may even be considered 
mildly beneficial, as they hasten natural pruning of the lower branches. 
The species is fairly common in Mississippi, 1s known from Florida and 
South Carolina, and is widely distributed. The known hosts include 
shortleaf pine, slash pine, and longleaf pine. 
The genus MZ/yeloborus Blkm. contains two eastern species which 
construct their burrows in the pith of the needle-bearing portion of 
living pine twigs. They are small, black bark beetles, very similar in 
gener ral appearance to Pityophthorus (p. 331), but differ in the struc- 
ture of the antennal club, which is not septate. Both species breed in 
and kill the leaf-bearing twigs of pine. The entrance gallery passes 
directly through the thin bark and sapwood, into the pith. Here it 
is enlarged to ‘form a nuptial chamber, from which two egg galleries 
proceed - in opposite directions. The larvae feed on wood, pith, and 
bark, killing the twigs. The place of entrance is marked by a small 
but conspicuous white or cream-colored pitch tube. Only a few eggs 
are laid in each burrow, the adults emerging and attacking a new 
twig. Attacks occur most frequently on the lower branches of the 
sides of the tree most exposed to sunlight. The dying of twigs on 
these lower branches is conducive to the production of clear lumber. 
