INSECT ENEMIES OF EASTERN FORESTS 323 
numbers on the surface of the bark that is being attacked by the 
scolytids, and they destroy many of the beetles. Swaine (402) pointed 
out the efficiency of hymenopterous parasites. The writer has also 
observed cases where sometimes as high as 90 percent of the pupal cells 
of Leperisinus aculeatus were occupied by parasitic cocoons. 
Leperisinus aculeatus, the common eastern ash bark beetle, is 
from 2.5 to 3 mm. long. It is dark brown, variegated with lighter 
tan or ashy scales. It is the most common and widely spread species 
of the genus, occurring in Canada from the eastern coast to Manitoba 
and in the United States from Maine to Kansas and southward to the 
Gulf of Mexico. It attacks various species of ash. ZL. fasciatus Lec., 
the white-banded ash bark beetle, is smaller, ranging from 1.5 to 2 
mm. in length, and is black with white markings. It is not so common 
as the former but is widely distributed, specimens having been col- 
lected in New York, New Jersey, Pennsylvania, Maryland, the District 
of Columbia, West Virginia, and Indiana. 
The native elm bark beetle (/ylurgopinus rufipes) is a mod- 
erately stout, brown beetle, from 2.25 to 2.75 mm. long. The eyes 
are long and oval, without emargination; the antennal funicle is seven- 
jointed, and the club is elongate oval, with three distinct sutures. The 
pronotum is closely punctured, and the elytral striae are impressed 
and coarsely punctured (fig. 61, £). 
This species is widely distributed throughout the Eastern States 
and is notably more common in the more northern States than in those 
farther south. Because this insect is associated with the Dutch elm 
disease fungus in the infected areas near New York City and else- 
where, and is known to be a vector, the information on its distribu- 
tion is more complete than it was a few years ago. It is now known 
to occur in eastern Canada, New Hampshire, Vermont, Massachusetts, 
Connecticut, Rhode Island, New York, New Jersey, Pennsylvania, 
Delaware, Maryland, Virginia, West Virginia, Ohio, Indiana, Min- 
nesota, Missouri, Kansas, Kentucky, Tennessee, Alabama, and Mis- 
sissippi. The beetle is recorded from various species of elm and from 
basswood. 
The native elm bark beetle is not an agressive insect, as it successfully 
attacks only diseased, dying, broken, or cut material. The burrows are 
of the transverse, forked type and can readily be distinguished from 
those of the smaller European elm bark beetle (Scolytus multistria- 
tus) which are longitudinal. The beetles complete one or more gen- 
erations a year, depending on the climate, and pass the winter either 
as larvae or adults. Many of the young adults emerge in the fall and 
burrow into the bark of either the trunks or limbs of living elm trees, 
especially in the lower trunk, where they hibernate during cold 
weather. They often bore through the bark to the wood and doubt- 
less obtain nourishment during warmer periods from the living 
inner bark. 
Experiments at the Forest Insect laboratory at Morristown, N. J., 
indicate that if such hibernating young adults have emerged from 
bark infected with the Dutch elm disease fungus, they carry the fungus 
with them, and if these spores are deposited in the wood of healthy 
trees, such wood often becomes infected. When confined in cages, 
Hylurgopinus rufipes will also feed in the crotches of young twigs, 
but it is not known that they do this in nature. Since they often breed 
