44 College of Forestry. 
The manner of feeding depends upon condition of tem- 
perature and moisture. If the temperature is low and the 
host dry, the burrows groove the sapwood rather deeply, 
whereas if the weather is warm and the limb quite moist, 
the feeding burrows are likely to be entirely or nearly en- 
tirely in the bark, especially if this is comparatively thick. 
After feeding only a short time — two or three days at the 
most — the still callow adult bores through to the outer bark 
and makes a minute opening through the surface (Fig. 29). 
This is the so-called ventilation opening by means of which 
the feeding young beetle receives a better supply of air and 
through which he casts out the refuse from his burrow. 
This refuse consists largely of excrement but also contains 
considerable material excavated in its burrowing which has 
never passed through its body. This material is pushed out 
through the minute “ ventilation openings” and collects in 
little hillocks over each such opening. The feeding burrows 
(Figs. 27, 28) of the young adults are built according to no 
uniform plan as are the other burrows. Some are long bur- 
rows but little greater in diameter than the insect inhabiting 
them, while others are short and broad or of irregular shape. 
Very often the feeding burrows of two or more beetles 
coalesce (Fig. 28) rendering the engraving still more 
irregular. 
The length of time the young adults continue feeding in 
the larval host varies considerably from a week to several 
weeks. If the bark is allowed to dry they leave much sooner 
than when it is kept quite moist. Beetles have been induced 
to remain in their larval host for as long as five weeks by 
keeping this quite moist, while others sought a new host 
within a week after reaching adult condition if the old host 
was allowed to become too dry. It is worthy of note, how- 
ever, that these latter on entering fresh pine limbs placed for 
them nearly all constructed feeding burrows, while those 
emerging after a longer period of feeding, immediately busied 
themselves making brood burrows. It would seem that sev- 
eral weeks of feeding, either in the old host or in a new one, 
is necessary before the adults can reproduce. It is apparent 
