PINE BARK-BEETLES. 707 



" The wood-engraver bark-beetle is the most cominou and probably the 

 most pernicious of all the insects infesting the forests of white pine in 

 the State of New York, and of yellow j)ine (P. variabilis) in the States 

 south of us. Whilst it is old and decaying or dead trees that most of 

 the larger borers which we have described above attack, this small in- 

 sect is liable to invade trees that are in full health and vigor, those that 

 are young as well as old, mining beneath the bark and loosening it from 

 the wood, so completely separating it that it breaks ofi" in large pieces. 

 Frequently, on elevating this loosened bark, its inner layers and the 

 whole outer surface of the wood are found plowed in every direction, and 

 the furrows are so intricate and confused that it is impossible to follow 

 the track which any one individual has traveled. But in places where 

 they have been less numerous, the work which each insect has per- 

 formed is distinctly marked and is so regular and artistic in its appear- 

 ance as to have suggested to Mr. Say the name of the wood-engraver 

 as a most appropriate designation for this beetle. The cut on the fol- 

 lowing page is an exact copy of the tracks made by one of these beetles 

 and its young, their natural size.* It will be seen to consist of a main 

 central track running nearly straight, from which numerous smaller 

 short ones branch off at nearly right angles. Though I have not ob- 

 served the habits of these insects sufficiently to be perfectly certain 

 respecting all the points in their operations, the course they pursue in 

 forming these tracks appears to be as follows: The female having 

 selected a situation which will furnish suitable sustenance to her young, 

 bores through the bark to the outer surface of the wood, and then mines 

 a passage between the bark and the wood, in a straight line lengthwise 

 of the tree or limb where no obstructions occur to cause her to deviate 

 from her course. The male probably accompanies her and shares with 

 her in this labor, each working by turns. Thus a long slender cylin- 

 drical gallery is formed, which is excavated about equally in the outer 

 surface of the wood and in the inner layers of the bark. In some in- 

 stances, two, three, or even six tracks will be seen to start from one 

 point, running in opposite directions, but always lengthwise of the tree 

 or limb, and with lateral branches so similar to those in the figure that 

 I am in doubt whether they are the work of this or one of the other 

 species which belong to this tree. Upon each side of the main tiack 

 little notches are excavated at intervals, whilst the work is in progress, 

 similar to those represented in our figure of the tracks of the pine bark 

 beetle on the succeeding page, though larger than those, being about 

 equal to the width of the track in their length, but less in their width, 

 and having their outer ends evenly rounded. In each of these notches 

 from one to four eggs are placed. And as the beetles mine their way 

 onwards, the fine dust which they form probably becomes strewed along 

 the track behind them. Then, as they travel backwards and forwards 

 in the burrow from time to time, the little stiff hairs with which their 



* The cut is not reprod uced. 



