816 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
An investigation shown! pretty conclusively that an insect was the cause of the 
death of the ti. «■-. A minute bark-mining beetle, both in its mature and in its larval 
state, was found between the bark and the wood. The beetle perforates the bark, 
excavate-, its furrow along the inner surface in a horizonal direction, and deposits its 
Jong the sidesof the furrow, which is less than one-sixteenth of an inch in diam- 
eter. As soon as the eggs are hatched, the lar\ ■ begin to mine furrows of their own 
at right angles to the original gallery, one part eating their way upward and another 
downward between the bark and the wood. These larval galleries are nearly parallel 
li other, and are at their beginning so minute that they are scarcely visible to the 
naked eye ; but as the larva advances in its course it increases in size and the diam- 
eter of its furrow increases in like manner. The larva' were found ( in some instances 
transformed to the mature beetle ) each in the larger endof its own furrow. It will be 
observed from the direction of the original furrow how powerful an agent for mischief 
this minute beetle is. Ite work is carried on in the most vital part of the tree. Three 
or four beetles attacking the trunk at or about the same height and on different sides 
of the tree would completely and effectually girdle it and destroy its life. Even a 
single beetle, by extending its furrow entirely around the trunk, would accomplish 
the same result, but no furrows were found thus extended. The length of the origi- 
nal furrows appeared to be less than 4 inches. The beetle itself is scarcely more than 
one line long, and belongs to the genus Tomicus. The species is probably undescribed. 
In the case of the spruce-destroying beetle more workers are necessary to kill the tree 
because the main furrows are excavated longitudinally or parallel to the axis of the 
trunk, while in the case of the balsam-destroying beetle the original furrow is exca- 
vated at right angles to this axis, and therefore cuts off or destroys the vital action 
over a much broader space. 
The destruction of the balsams was not limited to the single grove in which it was 
first observed. In several places along the road between Summit and Jefferson dead 
and dying balsams were noticed ; but the affected trees were not very numerous, and 
it would not be a difficult matter, with prompt and united action, to arrest the prog- 
ress of the mischief. If each man, on whose land the balsams grow, would, as soon 
as signs of the presence of the trouble are manifest, cut the affected trees, strip off the 
bark and burn it, he would, by so doing, destroy the colonies of larvre and prevent 
the further spread of the mischief. It is not at all probable that trees once attacked 
and showing signs of death can be saved, and it would be far better to cut them im- 
mediately than to allow them to remain as nurseries for these tiny marauders. 
The spruce aud firs in tbe Adirondack^, however, seem in general 
less affected than in Maine. Mr. John H. Sears, an observing botauist 
of Salem, Mass., who made a trip there late in the summer of 1881, 
writes me that " the spruce and other coniferous trees are remarkably 
healthy, noticeably so from Ticonderoga, Essex County, through Clin- 
ton County to Rouse's Point ; and in Canada northward to Montreal, 
from Lyon Mountain to Chateaugay, there are large and handsome 
specimens over three feet in diameter. 
A writer also called attention in 1883 to the death of spruces, in a 
letter to the Nation, under the heading u Decay of Spruce in the Adir- 
ondacks, M which we copy : 
To the Editor of the Nation: 
Sir : Apropos of your recent article on " The Adirondack Forest," there is a dan- 
ger now menacing, and even upon, the Adirondack forests much more serious than 
the lumbering you fear (though that has been going ou in a large way for certainly 
thirty years past), in the gradual dying out, from some unexplained cause, of th9 
spruce timber. In one of the large untouched tracts in Essex county, where the pro- 
