440 FIFTH KEPORT OF THE ENTOMOLOGICAL COMMISSION. 



Beyond the cell there is a transverse continuous line, broader than the rest, and out- 

 wardly bent over median nervules. The brown color is blackish over nearly two- 

 thirds of the primaries from the base, and outwardly gray ; hind wings rounded in 

 both sexes, with blackish haire at base, pale and subpellucid, with short gray fringe, 

 before which there is a narrow blackish edging. The abdomen is blackish. The males 

 are smaller than the females. The smallest male expands about 40"'™, the largest 

 female over GO'"™. (See Plate I, Figs. 10, 11, and 12.) While thus far the Centre 

 (N. Y.) locality has proved to be the chief home of this Cossus, it will undoubtedly 

 be found elsewhere wherever the Populus tremuloides 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 in one instance a pupa-case was found 

 in a tree measuring 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 than where the larvae 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 kindling-wood. The months of October, April, and June were selected as 

 suitable times for such investigations. October 14 we visited a tree for the purpose 

 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 seventeen 

 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 larvse ; only about 4 feet of the trunk was alive, 

 with a few lateral branches in foliage, scarcely enough to support its respiration. 

 In the trunk were found fresh pupa-cases, pupae, and caterpillars. Again three crops 

 of larv«e 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 taken their last position preparatory to their final 

 transformation into pupae. Pupie were also found occupying the same position, and 

 when the bark was removed were visible. 



The larva taken October 14 from its burrows is 45™™ in length, of a pale flesh 

 color. It is a little broader anteriorly. The prolhoracic 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 

 antennae 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 movfs with freedom 

 either backward or forward. The burrows which it excavates are about 1.5™™ in 

 width and terminate in the pupating cell, which is about 40™™ in length, smooth; 

 the extremity towards the opening is closed by a wad of finer and then coarser filings 

 of the wood. The coarser splinters are not detached entirely from the wood, but 

 are split up by the larvae 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, Fig. 7) is about 40'°™ from the outer bark of the tree, acd the 

 chrysalis (Figs. 8 aud 9) makes its way to the air though the burrow, by means of 



