14 College of Forestry. 
before constructing their brood burrows. The feeding bur- 
rows are a continuation of the larval and pupal burrow and 
at this season of the year are excavated nearly entireiy from 
the sapwood (Figs. 27-28). Those occupied as winter 
quarters have never been observed to possess the so-called 
* ventilation ” openings which are so characteristic at other 
seasons. 
There is good reason for believing that P. hopkinsv hiber- 
nates in the true sense of the word only during the coldest 
winter weather. Burrows opened on mild days in Decem- 
ber contained larvae and young adults which were quite 
active and were evidently still feeding. On being brought 
into a warm room from freezing winter weather, the adults 
show signs of life as soon as the bark is removed and _be- 
come active in a very few minutes. This was shown on 
several occasions when beetles removed from burrows in 
frozen bark began creeping over fresh limbs of pine within 
ten minutes and several actually began new burrows within 
an hour. Some of these burrows were later found to be brood- 
burrows. Specimens of /ps pint Say removed from the same 
limbs remained torpid for a much longer time. 
Emercence.— With the first warm days of spring the 
over-wintered larvae and adults begin feeding voraciously. 
For several days the adults allow their burrows to remain 
closed, feeding industriously in the meantime. These bur- 
dows while they still groove the sapwood include also con- 
siderable of the inner bark. After a few days of feeding 
they carry their mines well out into the outer bark and soon 
make a minute opening through this to the outside (Fig. 
29). This opening is usually spoken of as a “ ventilation 
opening.”’ Its main purpose, however, seems to be to serve 
as a means of disposing of the excrement and the surplus 
frass produced by the adult, although it doubtless serves for 
ventilation also. Small hillocks of ‘‘ saw-dust ” soon appear 
in great numbers on the surface of the bark and if these are 
blown or brushed away it will be seen that each one has 
covered a small irregular opening through the bark. When 
first made this opening is the size of a small pin hole, but as 
