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164 INSECTS INJURIOUS TO FOREST AND SHADE TREES. 
most pernicious of all the insects infesting the forests of white pine in 
the State of New York, and of yellow pine (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 hable 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 off 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 cylindri- 
eal gallery is formed, which is excavated about equally in the outer sur- 
face of the wood and in the inner layers of the bark. In some instances, 
two, three, or even six tracks will be seen to start from one point, run- 
ning 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 track, little 
notches are excavated at intervals, whilst the work is in progress, simi- 
lar to those represented in our figure of the tracks of the pinebark- 
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 
bodies are bearded, serve as a brush to sweep this dust into these lat- 
*The cut is not reproduced. 
