REPORT OF THE BOTANIST. 35 
from one-half to two-thirds of the spruces with a basal diam- 
eter ranging from one to two feet were either dead or dying. 
Trees of this size are the most suitable for lumber and conse- 
quently the most valuable. The smallest affected tree noticed, 
had an estimated basal diameter of about ten inches. In this 
case the attack appeared to be a failure, for so much resin had 
oozed from the wounds that the work was obstructed. The 
galleries were scattered and single and their authors were 
found dead, each in its furrow. No larve. were present, and 
the apparent attempt to establish a colony in this tree had 
thus far failed. But it may be that this tree had only been 
attacked for the purpose of obtaining food, and had not yet 
been brought into that sickly, languishing condition thought by 
some entomologists to be necessary to induce the establish- 
ment of a colony, the deposition of eggs and the develop- 
ment of larve. For it is said of Scolytus destructor, a bark- 
mining beetle that sometimes proves very destructive to elm 
trees in Europe, that the adult insects first attack healthy 
trees for the purpose of obtaining food, and when, by this 
means the vigor of the tree has become somewhat impaired, 
the female deposits her eggs in her galleries. Then the rapidly 
increasing numbers soon destroy the life of the tree. 
W hen two trees of unequal size stand in close proximity 
the larger one seems to be most liable to be attacked. In 
one instance two trees stood scarcely more than three feet 
apart. The larger one had been attacked; the smaller 
remained unharmed. In another similar instance the larger 
of the two trees was dead, having been attacked first; the other 
was dying. Why this preference on the part of these insects 
for the largest trees? It may be that young trees are apt to be 
too resinous to be attacked successfully. In the case of the 
small tree already mentioned the gummy exudations from the 
perforations in the bark first attracted my attention. Or the 
insects may instinctively know that a tree with a large trunk 
presents a broader field for their operations than one with a 
small trunk ; or possibly the vigor of the tree may be so im- 
paired by age that it is more readily brought into suitable 
condition for the habitation of these parasites. Whatever the 
cause of this selection, no diseased condition of the trees was 
detected except that which was accompanied by and to all 
appearance was directly due to the insects themselves. Cer- 
