DESTRUCTION OF SPRUCE FORESTS. 821 
three species, Pityophthorus puberulus, Xyloterusbivittatus, and Xyleborus 
ccelatus, being the principal aggressors. 
That the disease was not due to fungi has been shown by a thor- 
oughly competent botanist, Prof. Charles H. Peck, of Albany, N. Y. 
That it was not due to extremely cold weather in winter is probably cer- 
tain, from the fact generally observed by us that spruce and fir forests, 
over any given area, are not universally killed, as among groves of dead 
spruces and firs many living perfectly healthy trees exist, while the pines 
and hemlocks have been unharmed. By cutting down portions of for- 
ests and thus letting in cold, severe winter blasts, general and wide- 
spread destruction of entire forests may ensue, as has been shown to 
have been the case in France. Why pine trees should have, in general, 
escaped the ravages of these beetles, all of which we have found in 
greater or less abundance under the bark of dead pines, and especially 
in dead stumps, we can not explain, except from the well-known fact 
that most vegetable-eating insects prefer one species of tree and retain 
that preference for successive generations. 
Our experience teaches us that not only spruces, firs, and pines are 
attacked and killed by boring beetles, but the experience of others, 
notably that of Dr. 0. Hart Merriam, shows that entire groves of sugar- 
maple saplings in northern New York have been killed outright by a 
little bark-borer (p. 389). The following extract will show the nature 
of the attack and the result to healthy, living trees : 
About the 1st of last August (1882), I noticed that a large percentage of the under- 
growth of the sugar-maple in Lewis County, northeastern New York, seemed to be 
dying. The leaves drooped and withered, and finally shriveled and dried, but still 
clung to the branches. The majority of the plants affected were bushes a centimeter 
or two in thickness, and averaging from 1 to 2 meters in height, though a few 
exceeded these dimensions. On attempting to pull them up they uniformly, and 
almost without exception, broke off at the level of the ground, leaving the root 
disturbed. A glance at the broken end sufficed to reveal the mystery, for it was 
perforated, both vertically and horizontally, by the tubular excavations of a little 
Scolytid beetle which, in most instances, was found still engaged in his work of 
destruction. 
At this time the wood immediately above the part actually invaded by the insect 
was still sound, but in a couple of months it was generally found to be rotten. 
During September and October I dug up and examined a large number of apparently 
healthy young maples of about the size of those already mentioned, and was some- 
what surprised to discover that fully 10 per cent, of them were infested with the 
same beetles, though the excavations had not as yet been sufficiently extensive to 
affect the outward appearance of the bush. They must all die during the coming 
winter, and next spring will show that in Lewis County alone hundreds of thousands 
of young sugar-maples perished from the ravages of this Scolytid during the summer 
of'l882. 
As has been stated in our Bulletin on Forest-tree Insects, it -is well- 
known that healthy, large sugar-maples are often attacked and killed 
outright by the borer which attacks that valuable shade tree. The in- 
stances of the death of healthy trees of various kinds from the attacks 
of internal pests or of bark-boring beetles are so numerous that we 
