OAK-BORERS. 57 
whereby the hole inside is less liable to be discovered by birds. The worm then dili- 
gently lines the walls of this hole with silken threads interspersed with its chips and 
forming a rough surface resembling felt, as it withdraws itself backwards for a dis- 
tance of about three inches, thus placing itself beyond the reach of any bird or other 
enemy outside of the tree, should its retreat be discovered ; and it here incloses itself 
in a cocoon which it spins of silk, of a long oval form, having the end towards the 
outer opening much thinner and its threads more loosely woven. In this cocoon it 
throws off its larva skin and then appears in its nymph or pupa form. 
The pupa is an inch and three-quarters long and half an inch thick, of a dull chest- 
nut color, the rings of its abdomen paler, and on the back near the anterior edge of 
each ring is a row of angular teeth, resembling those of a saw, of a dark brown color 
and all of them inclining backward, these rows of teeth extending downwards upon 
each side below the breathing pores or about two-thirds of the distance around the 
body. On the middle of each ring is also a much shorter row of little tubercular points. 
Finally, upon the under side of the last segment are about four stouter conical teeth, 
the tips of which are drawn out into sharp points which are curved forward, so that 
when this last segment, which is tapering and smaller than the others, is bent down- 
wards these curved points will catch and hold the body from moving forward. 
The pupa lies perfectly dormant in its cocoon probably a fortnight or longer. It 
then awakes from its slumbers and begins to writhe and bend itself from side to side. 
By this motion the rows of little teeth upon the rings of its abdomen, which incline 
backward as above described, catch in the threads of the cocoon, first upon one side 
and then upon the other, and thus move the body forward, whereby its head presses 
upon the loosely woven end of the cocoon, more and more firmly, until it forces its 
way through it, and the pupa works itself forward out of its cocoon. And the same 
writhing motion being continued, the teeth now catch in the threads with which the 
sides of the hole are lined, and thus, though destitute of feet, the pupa moves itself 
along till it reaches and breaks through the thin scale of bark which hitherto has 
closed the mouth of its burrow, and pushes itself onward till about three-fourths of its 
length protrude from the tree, when by curving the tip of its body downward the 
four little hooks thereon catch in some of the threads and hold it from advancing 
further and falling to the ground. By so much motion of the pupa the connections 
of the inclosed insect with its shell become sundered and the sutures of the shell are 
probably cracked open, so that the moth readily presses them apart and crawls out 
therefrom, leaving the empty and now lifeless shell projecting out from the mouth of 
the hole, with a small mass of worm-dust surrounding it. 
The male moth is of a gray color from white scales intermixed with black ones. The 
head is furnished upon the crown, or vertex, with longer or hair-like scales. The 
antennae are tapering and many-jointed, their basal joint thickest and covered with 
black and gray scales, the remaining joints being naked, shining, coal-black, each 
joint bearing two branches on its front side, forming two rows of coarse teeth like 
those of a comb, the teeth being six or more times as long as thick, and all of the same 
length except at the base and tip, where they become shorter, all of them ciliated with 
fine hairs. The feelers are appressed to the face and reach as high as to the middle 
of the eyes, and are cylindric, clothed with short appressed scales, the separation of 
the terminal joint being slightly perceptible. The thorax has the shoulder-covers 
black, forming a stripe of this color along each side, which anteriorly curves down- 
wards and is continued backward upon the upper side of the breast. Its base is 
clothed with larger scales, forming tufts upon each side. The abdomen is conic and 
equals the tips of the wings in its length, and is but slightly covered with scales except 
along each side, where they form a broad stripe, the under side being ertirely de- 
nuded; it is black and shining, with the sutures dull yellowish. At its tip are three 
appendages, longer than the last rings of the abdomen. The two lower ones are broad, 
thick, flattened processes of a dull brownish yellow color, with their tips rounded and 
slightly bent inwards towards each other. The upper one is a slender, black, shining 
hook or claw of the same length, its tip sharp-pointed and curved downward. Above 
