THE PEACH-TREE BARKBEETLE. 95 
tree about 14 inches in diameter and from 75 to 80 feet high which 
had apparently been killed by the beetles, the bark having been 
completely eaten away from the tree. 
The adults or beetles (see fig. 20, a, b) produce the primary injury 
to healthy trees, the work of the larve being secondary. The healthy 
trees, by repeated attacks of the adults, are reduced to a condition 
favorable to the formation of egg burrows. When the beetles are 
ready to hibernate in the fall they fly to the healthy trees and form 
their hibernation cells. These latter are injurious to the trees, for 
through each cell there will be a tiny flow of sap during the following 
season. (See Pl. XI, fig. 2.) 
The greater the number of hibernation cells, the greater will be the 
amount of sap exuded; also, when the beetles come out of their winter 
quarters in the spring they bore into the bark of healthy trees from 
one-quarter to one-half of an inch, either for food or in an endeavor 
to form egg burrows. Later the beetles leave these burrows, either 
because the burrows become filled with sap or because the beetles seek 
the sickly trees for breeding purposes. Many more small channels 
are thus formed in the bark and from these sap oozes during the 
summer. Two means are therefore supplied by which the sap may 
flow from the trees—and this it does in many cases, forming large 
gummy masses around the trunks. Such losses for three or four years 
in succession necessarily reduce the trees to a very much weakened 
condition, and it then becomes possible for the beetles to form egg 
burrows and for the larve to finish the destruction of the tree. Plate 
XI, figure 3, shows the remains of an orchard presumably killed by 
Phleotribus liminaris. 
LIFE HISTORY. 
HIBERNATION. 
The insects spend the winter as adults in hibernation cells just be- 
neath the outer layer of bark on both healthy and unhealthy trees. 
In the fall, from October to freezing weather, the adults of the fall 
generation are continually emerging and migrating to growing trees. 
They bore in through rough places on the bark and burrow along 
from one-quarter to five-eighths of an inch, forming hibernation cells, 
the openings to which are closed with the exudation from the bur- 
row. In these cells they remain throughout the winter. The latest 
formed adults of the fall brood remain in the pupal cells until spring 
before cutting out, so that hibernation occurs both on dead and living 
trees, those on the live trees hibernating in regular hibernating cells 
and those on dead trees hibernating in the pupal cells. 
