336 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
structure at the posterior end of the concavity is much reduced. O. cae- 
latus is usually about 3 mm. long, with three teeth at each side of the 
concavity at the rear end, with the second and third slightly within the 
margin. ‘This species occurs in eastern Canada and in the United 
States as far south as Florida. It breeds in the thicker bark at the 
bases of pines of all species, and in spruce and larch. It is less ag- 
gressive than most of the eastern species of /ps and is aisuncely a sec- 
ondary species. The brood galleries are radiate, but the egg galleries 
are shorter than in /ps, the egg niches are larger and fewer in number, 
and in each from two to six eggs are deposited. 
The genus Pityokteines Fuchs. is also represented in the Eastern 
States by only one species, P. sparsus. It is of the same general 
type of structure as Jps, but here the shelf at the rear end of the poste- 
rior concavity is even more reduced than in Orthotomicus. The three 
teeth at each side are strongly developed in the males, but weakly de- 
veloped in the females, and these are further distinguished by the long, 
yellow hairs arising from the front of the head and from the apical 
margin of the pronotum. 
The single eastern species, Pityokteines sparsus, the balsam fir 
beetle, is slightly less than 2.5mm. long. Its distribution corresponds 
closely with ‘that of its usual host, the eastern balsam fir. It breeds in 
balsam fir slash, and is also often found in the bark of the trunk and 
limbs of firs that have died suddenly, as indicated by rapidly fading 
foliage. It has, therefore, often been classed as a primary enemy of 
eastern balsam. This is doubtful, however, because a thorough ex- 
amination will usually reveal that such trees were in a very decadent 
condition when attacked by the beetles. It is also reported from 
eastern larch. 
The genus Yryocoetes Eichh. is not very closely related to Zps, but is 
discussed here because of similarity of habit. In Dryocoetes the 
pronotum is more feebly arched than in /ps and is more or less gran- 
ulate over the entire surface. The rear end is not truncate, or ex- 
cavated, but convex or slightly flattened, and weakly gr anulate. 
Dryocoetes breeds in sever: al species of conifers and hardwood trees. 
Logs or decadent trees are preferred, and the eastern species are not 
known as killers of trees. The burrows are of the radiate type, but in 
some species are often very irregular. These species have been in- 
cluded in those discussed by Swaine (407) in 1918, Blackman (38) in 
1922, and Chamberlin * in 1939. 
Dryocoetes americanus is 3 to 4 mm. in length and occurs in the 
Northeastern States and as far west as the Rocky Mountains. It 
breeds in species of pine, spruce, and larch. It isa secondary species, 
breeding by preference in cut or broken material. D. piceae is 
much smaller, averaging about 2.5 mm. in ‘length, and is very closely 
related toa western species, )). affober Mannh., which is shghtly larger 
but otherwise similar. It breeds in pines and spruces in its range from 
Maine to Colorado. It is not aggressive and favors dying or cut ma- 
terial. D, betulae ranges in length from 2.5 to 4.5 mm. and breeds in 
the bark of birches, beech, and occasionally wild cherry when these 
are decadent. The southern variety, known as D. liquidambarus 
Hopk., is found in red gum in the Southern States. 
77 See footnote 22, p. 302. 
