50 BULLETIN NO. 3, DIVISION OF ENTOMOLOGY. 
in front than in Vystus, not so elongate or so elevated dorsally. The 
male antenne are bipectinate; the lamelle rather short and ciliate. 
The female antenne are serrated. It is allied to the European Cossus 
terebra F., but is a larger insect. It differs from C. querciperda Fitch 
by the absence of any yellow on the male hind wing, and by its darker 
color and closer reticulations. 2 
In color this species is black and gray. The edges of the thorax and 
collar are shaded with gray, more noticeable on some specimens than 
others. The primaries are covered with black reticulations, which are 
not always identical in their minor details in different specimens, nor 
sometimes on both wingsin the same specimen. Beyond the cell there 
is a transverse continuous line, broader than the rest, and outwardly 
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 hairs at base, pale and sub- 
pellucid, with short gray fringe, before which there is a narrow black- 
ish edging. The abdomen is blackish. The males are smaller than the 
females. The smallest male expands about 40™", the largest female 
over 60™™ (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 larve 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 in- 
dications 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. A1Il of them were actively 
passing through their tunnels in the wet wood, through which the sap 
was freely flowing. Not any of the caterpillars 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 larve; 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, pups, and 
