INSECT ENEMIES OF EASTERN FORESTS 339 
Massachusetts to Colorado and southward. The hosts include blue- 
berry, rhododendron, and mountain mahogany. 
The genus d/onarthrum Kirsch contains two eastern species, one 
slightly less than and the other shghtly more than 2.5 mm. long, and 
a third as wide. The antenna has a two-jointed funicle. Both species 
breed in the sapwood of eastern hardwoods, making very slender black- 
stained galleries of the compound ambrosial types. They attack only 
dying, injured, or recently cut trees, and their burrows in logs left 
unsawed too long reduce the value of the product. J/. mali Fitch is 
of a nearly uniform brown color, and averages about 2.3 mm. long. 
It is common throughout the eastern half of the country as far south 
as Florida and injures the wood of all species of deciduous trees, in- 
cluding fruit trees. J/. fasctatum Say is shghtly larger than J/. mali 
and is readily recognized by a pale yellow band across the middle of 
the wing covers. It occurs throughout the eastern part of the United 
States, but is much more common in the South and lacking or rare in 
the extreme North. It infests most of the eastern hardwoods. 
The genus XY yloterinus Swaine is represented by a single species, X. 
politus Say. Specimens average slightly more than 3 mm. long, 2.6 
times as long as wide, and are dark brown to black with the wing 
covers paler. This species ranges throughout the Eastern States and 
Canada. It occurs in many of the common eastern hardwoods and has 
been taken in hemlock. The burrows are of the compound ambrosial 
type. 
The genus 7rypodendron Steph. contains four eastern species, two 
of which injure hardwoods and two coniferous wood. They are small, 
stout beetles from 3 to 4mm. long, dark brown or black, usually marked 
with bands or stripes of yellow. All prefer dying or recently cut wood 
in which to breed, and all construct the compound ambrosial type of 
galleries. Z. scabricollis ranges from 3.1 to 3.6 mm. in length, 
and is dark brown or black, sometimes with indistinct stripes on the 
wing covers and a similar band on the pronotum behind. It occurs 
from New York to Mississippi and westward to New Mexico. It 
breeds in pines and is also said to attack hemlock and witch-hazel. 
Trypodendron retusus is the largest eastern species, being 3.5 to 4 
mm. in length, with a broad stripe of smoky yellow on each wing cover. 
The males have the pronotum broadly emarginate in front. It is 
rather common in species of Populus in the northern tier of States, 
and its range extends from eastern Canada to West Virginia. 7. betu- 
lae ranges from 3 to 3.5 mm. in length, and has a broad stripe of 
yellow on each wing cover and an indefinite yellow band on the prono- 
tum behind. Several species of birch serve as hosts, and the range of 
the beetle comprises eastern Canada and the Northeastern States, and 
also Minnesota. 7’. bivittatum is about 3 mm. long with color mark- 
ings similar to those of 7. betulae but is readily distinguished in 
the field by its hosts, which consist of pines, spruces, arborvitae, fir, 
larch, and hemlock. Its range includes eastern Canada and the eastern 
part of the United States, and it is doubtfully distinct from western 
forms. | 
The genus @nathotrichus Eichh. contains two species of very 
slender reddish-brown beetles which are true ambrosia beetles, al- 
though structurally they are more closely related to Pityophthorus 
than to any group of ambrosia beetles. They are elongate, 314 times 
