INSECT ENEMIES OF EASTERN FORESTS 309 
sissippi and westward to Texas, Oklahoma, Kansas, and Minnesota. 
It has been reported, perhaps erroneously, from Utah, and is likely to 
be found wherever the various species of hickory grow naturally. 
Often the first indication of the presence of the ‘hickory bark beetle 
is seen in wilting leaves and hanging broken twigs on an otherwise 
normal hickory tree. These appear during early midsummer and 
are due to the activities of the recently emerged adults, which feed 
voraciously by boring into the petioles of the leaves and the young 
growth of the twigs. “The cavities made in feeding may extend nearly 
through twigs and petioles, causing the leaves to wither and the twigs 
to break and either fall to the eround or remain hanging by a few 
shreds of bark or woody tissue. The feeding of the young adults 
often does considerable damage to a tree, but does not kili it. 
Fatal injuries to hickory by these bark beetles are due to their breed- 
ing habits. The young beetles, after feeding for some time as pre- 
viously described, fly to the trunk and branches of living trees, bore 
through the bark to the surface of the sapwood, and there construct 
rather short, longitudinal egg galleries and deposit their eggs. The 
entrance to the burrow is nearly perpendicular to the surface of the 
wood, but with a slightly upward angle, and the egg gallery extends 
directly upward, with the erain of wood, at the contacting surfaces 
of wood and bark. In thick-barked hickory the wood is scarcely 
etched by the gallery, but in thin-barked limbs as much as half of 
the diameter of the burrow may be gouged from the wood. The egg 
galleries range from 1 inch to 31% inches in length, depending largely 
an we vigor of the tree attacked, the burrows being longer in dying 
ark, 
Usually from 20 to 60 eggs are placed in small pockets or niches 
at each side of the egg gallery, but in unusually long galleries as many 
as 140 have been observed. Upon hatching, the “larvae burrow in 
the phloem, starting in at right angles to the gallery. At first the 
larval mines are very narrow and straight, but as they increase in 
diameter they diverge more and more, finally producing a centipede- 
like engraving. 
When nearly full grown, the larvae leave the phloem and bore into 
the outer part of the inner bark. If they reach full growth in the 
fall, which they normally do in the Northern States, they remain in 
the bark over winter, and transform to pupae and later to adults the 
following spring or early in the summer. 
In the Northern States the hickory bark beetle has a single genera- 
tion a year, the adults being in flight during June and the early part 
of July. The foliage of trees attacked ustially begins to fade and fall 
by the middle of August, but in some cases fatally attacked trees 
retain nearly Petr full foliage until time for normal fall shedding. 
Farther south, e. g., in northern Mississippi, there are apparently two 
generations in aa year, the first attacks taking place early in May. 
The hickory bark beetle has caused the death of thousands of trees 
in New York, Pennsylvania, and other regions of the North, and also 
in Maryland and Virginia, and is by all odds the most deadly enemy 
of various hickories. When the beetles in an area are not ver y numer- 
ous, they breed in broken or cut material or in decadent or dying trees; 
but, when present in sufficient numbers, they attack trees that are ap- 
parently i in good health, killing hundr eds of them in a single season. 
