DESTRUCTION OF SPRUCE FORESTS. 821 



three species, Pityophthorus ptiberulus, Xyloterus bivittatus, and Xyleborus 

 c(elatns, 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 observ^ed b^'^ 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 kc.ilthy, living trees : 



About the Ist 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 aflfected 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 o£f 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 excavatious 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 1882. 



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 



