44< » FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
ml the eel] there is a trail let thau the rest, ami out- 
wardly bent over median nervules. The brown color is blackish over nearly two- 
thirds of the primaries from the base, and outwardly gray : hiud wings rounded in 
both sexes, with blackish hairs at base, pale ami subptdlueni, with short gray fringe, 
before which there U a narrow blackish edging. The abdomen is blackish. The males 
laller than the females. The smallest male expands about 40 mm , the largest 
Plate I. Pigs. 1". 11. and 1-2.) While thus far the Centre 
X. V.) locality has proved to be the chief home of this Cossus, it will undoubtedly 
be found elsewhere wherever the Populu* trtmuloides is found. Several pupa-cases of 
this species have been found in the corporate limits of Albany. Usually trees of less 
than 1 foot in diameter are attacked, although iu one instance a pupa-case was found 
in a trie measuriug 16 inches in diameter. 
It is a very different matter to observe the changes of insect life from the eggs to 
the imago when feeding upon the foliage of vegetation thau where the larv* have 
bored deep into a tree trunk and feed upon the ligneous fiber and its circulating 
fluids. To obtain this information it has been necessary several times each year to 
cut down trees bearing indications of its ravages, and to dissect them into fragments 
the size of kiudling-wood. The months of October, April, and June were selected as 
suitable times for such investigations. October 14 we visited a tree for the purpo:>e 
of obtaining caterpillars, and from a limb 4 feet in length six caterpillars were taken, 
two of which were occupying cells as seen in the engraving. 
April '2 we cut from a tree a limb 3 feet in length, and in it we found seventeeu 
caterpillars of three distinct sizes, indicating a growth for each year. The larger 
ones were not fully grown. All of them were actively passing through their tunnels 
in the wet wood, through which the sap was freely flowing. Not any of the cater- 
pillars were occupying pupa-cells at this time. June 12, 1881, we again visited a tree 
when the insects were emerging. The tree selected was far advanced in decay, from 
the effects of the tunneling of the larva? ; only about 4 feet of the trunk was alive, 
with a few lateral brauches iu foliage, scarcely enough to support its respiration. 
In the trunk were found fresh pupa-cases, pupa?, and caterpillars. Again three crops 
of larva? were found: the larger ones were inactive and lying in the sap-wood, with 
their heads close to the bark, which was gnawed nearly through to the outer surface. 
These caterpillars had evidently takeu their last position preparatory to their final 
transformation into pupa?. Pupa? were also found occupying the same position, sad 
when the bark was removed were visible. 
The larva taken October 14 from its burrows is 45 mm in length, of a pale flesh 
color. It is a little broader anteriorly. The prothoracic segment is blackish brown 
above, the dark color edged with dirty orange shading. The head is mahogany 
brown, shining, slightly roughened. The mandibles are black, with strong teeth. 
The surface of the head gives rise here and there to single scattered hairs. The 
antenna? are three-jointed : the second joint gives rise to a single long hair. The 
seventh, eighth, ninth, and tenth abdominal segments are provided with false feet. 
The segments are marked with a lateral row of brown dots above the reddish stig- 
mata, and there is a row of similar dots, two to a segment, on each side of the dorsal 
line. These dots give rise to single pale hairs. The larva inovts with freedom 
either backward or forward. The burrows which it excavates are about lo mm in 
width and terminate in the pupating cell, which is about 10 mm in length, smooth; 
the extremity towards the opening is closed by a wad of finer and then coarser tilings 
of the wood. The coarser splinters are not detached entirely from the wood, but 
are split up by the larva? all around the top of the cell, and project like bristles, 
appearing somewhat as those wooden toy trees which are made for children, and 
which are formed by shaving down the wood and leaving the shavings adhering by 
one end. These splinters make a firm wad. Against them are piled a quantity of 
finer chips or thin filings, which are loose but pressed together. 
The cell (Plate 1. F _ - about 40 mtn from the outer bark of the tree, aod the 
chrysalis (,Figs. 5 aud 9) makes its way to the air though the burrow, by means of 
