624 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



The discovery of the borer waa accidental. Passing along the border of a brook, 

 caiue upon some alders, A. incana, which had been drawn out root and branch upon 

 dry ground ; one stem had been broken oft' near the root, disclosing the cylindrical 

 gallery of an insect borer very diff'ereut from those made by a beetle larva common 

 in the same stems. An examination brought to light numerous examples of a Cossus 

 larva in the roots and stems of the alders in the vicinity. The facts in its history 

 were partially made out. 



Larvffi of two distinct sizes were about equally abundant; the larger ones at the 

 time, June 29, were molting. As the imagos probably had escaped, it seems pretty 

 certain that the preparatory stage lasts three years, i. e., the smaller larvae were one 

 year old, the larger two, and these transform next May or June. Several pui)a shells 

 (all broken) were found in the openings in the bark, and one pupa, which was dead 

 but in perfect condition. The larva, it seems, bores priucipally in the roots until the 

 second year, when it begins to work upward in the trunk, and before pupating in 

 the spring of the third year bores out to the surface a few inches above the ground. 

 The pupa cell, a mere enlargement of the burrow a little below the external opening, 

 is not stopped or plugged with chips as is the case in the cell of C. eetiterensis ; none 

 were found in the roots and no evidence was obtained that the larva bores in the 

 trunks save towards the end of its period, when it moves upward to prepare a way 

 for the moth to escape where it is out of the way of danger of water, as the alder 

 grows in wet places. This moth escapes as others of its kind do by the pupa worm- 

 ing its way out of the cell so that part of its body protrudes from the tree when the 

 moth emerges, leaving the skin in the opening. 



I will describe the larger of the larvae and compare the smaller one as it may 

 differ. 



Length, 1.5 to 1.8 inches. Subcylindrical, tapering very slightly at extremities, 

 slender, width of body .25 inch. Length of smaller ones .8 inch. The head is light 

 yellowish brown above, black about the mouth parts, hemispherical, smooth, or 

 slightly roughened, with a few dark dots from which arise dark hairs, usually worn 

 oft" the vertex of the larger examples. The second ring is smooth, lighter colored 

 than the head ; above the spiracle on either side there are three black spots situated 

 at the corners of a right-angled triangle; the upper one at the right angle bears a 

 coarse brown hair, the other two have finer, lighter-colored hairs ; the top of the third 

 ring is likewise smooth and brownish ; the remaining body surface excejjt the yellow- 

 ish j)iliferous spots and top of ring 13 is white ; the longer hairs on the posterior rings 

 are black. The body rings are strongly folded transversely ; the yellowish dorsal 

 spots bear brownish hairs; the anterior larger pair are situated rather near together 

 on the broadest transverse fold ; the smaller posterior pair are situated on a uari-ower 

 fold and much farther from the slight dorsal furrow. The stigmata are broadly 

 elliptical, the rings narrow, black scarcely raised above the surface, the color within 

 the ring Mght brown. The legs are yellowish, hooks black ; the prop legs with very 

 many booklets. 



The pupa is slender, length 1.6 inches, width of thorax .33 inch, but slightly curved 

 aud of unusually uniform diam.eter, smooth, under a lens transversely striate, the 

 three anterior rings black, shagreened; on the prothorax there are two conical pro- 

 tuberances which in profile under a strong lens prove to be double-pointed ; on the 

 clypeus are two gouge-shaped spines, shining black on outer half, and on the upper 

 roughened base of each of these there is a small conical tooth ; on the under side of 

 the head-case, below the gouge-like spines, is a pointed spine directed forwards ; 

 back of this are two smaller cusps, one either side of ventral line, and still farther 

 back, apparently over the first tarsal joint of the forelegs, are two smaller points; 

 the transverse rows of dorso-abdominal teeth are as usual, but the teeth are exceed- 

 ingly fine, increasing in size but little posteriorly ; the black, blunt, anal segment 

 bears several small black conical teeth on either side. 



