816 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



An investigation showed pretty conclusively that an insect was the cause of the 

 death of the trees. A minute bark-mining heetle, both in its mature and in its larval 

 state, was found between the bark and the wood. The beetle perforates the bark, 

 excavates its furrow along the inner surface in a horizonal direction, and deposits its 

 eggs along the sides of the furrow, which is less than one-sixteenth of an inch in diam- 

 eter. As soon as the eggs are hatched, the larvie 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 

 to each 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 larvaj were found ( in some instances 

 transformed to the mature beetle ) each in the larger end of its own furrow. It will be 

 observed from the direction of the original furrow how powerful an agent for mischief 

 this minute beetle.is. Its 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 neveral 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 laud 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 larvae 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 the Adirondacks, however, seem iu general 

 less affected than iu Maine. Mr. John H. Sears, an observing botanist 

 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 Eouse's Point ; and in Canada northward to Montreal, 

 from Lyon Mountain to Chateaugay, there are large aud handsome 

 specimens over three feet in diameter. 



A writer also called attention iu 1883 to the death of spruces, in a 

 letter to the Nation, under the heading " Decay of Spruce in the Adir- 

 ondacks," 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, aud even upon, the 'Adirondack forests much more serious than 

 the lumbering you fear (though that has been going on in a large way for certainly 

 thirty years past), iu the gradual dying out, from some unexplained cause, of the 

 spruce timber. In one of the large untouched tracts in Essex county, where the pro- 



