58 College of Forestry. 
tacking and killing limbs of pine which had been weakened 
by the earlier work of the pine bark aphis, Chermes pim- 
corticis Fitch. They seemed to find conditions here greatly 
to their liking, as the limbs were still alive and green, but 
apparently much of the sap had been extracted by the aphis 
and the resistance of the limbs reduced. They are also often 
found in great numbers in sickly small pines, especially in 
plantations, where they very rapidly kill small trees which 
would otherwise probably survive. They often attack these 
young trees while the foliage is still green and the bark green 
and sappy, and while many of the beetles succumb to the flow 
of pitch and die in their burrows, enough often succeed in 
building pitch tubes and disposing of the pitch to insure the 
death of the tree. Trees thus attacked are always small ones, 
varying in height from 4 to 15 feet, and the bark upon all or 
most of the trunk is still tender and it is this thin bark upon 
the trunk that is attacked. White pines which are weakened 
by transplanting are also attacked and killed in this way. In 
the summer of 1914 several pine from 4 ft. to 6 ft. high 
which had been transplanted early in the spring were ob- 
served to have been killed by the work of this little beetle. 
That the beetle enters the bark while it was still alive was 
shown by the numerous small pitch tubes at the entrance bur- 
rows, and the success of their attack was evidenced both by the 
death of the trees and by the presence of large numbers of 
larvae pupae and young adults in the inner bark. 
As a usual thing then P. hopkinsi should be classed as 
neutral, but at times it is injurious in its effects. That it 
could under certain conditions do considerable injury there 
can be little doubt. But everywhere that white pine occurs 
there are so many recently killed, dying or sickly limbs that 
ample breeding places are provided. Usually the worst ac- 
cusation which can be substantiated against this beetle is that 
it is accessory to the death of trees which have been weakened 
by other enemies or causes, although it is doubtless true that 
the trees thus attacked would often survive were it not for the 
activities of these little beetles. However, P. hopkinsi can- 
not be classed with the extremely injurious forms of which 
there are so many in the same family. 
