Sept. 1898.] 
Kunze : Two Forms of Cerura nivea. 
193 
longed to one brood and 1 to another, all but two larvae of the last 
died, affected by a fungus which previously existed in the breeding cage. 
As soon as larvae commenced cocooning and had the cells well walled 
the branches were removed into an envelope box, where the transforma¬ 
tion could go on undisturbedly, and permit cocoon to harden. The 
larvae gnawed off bits of epidermis from the cotton wood, and mixed 
with saliva, formed when hardened the silken frame for the wall of its 
cell. It would continue building on the inside of cocoon until of suffi¬ 
cient strength. On the external surface the cocoon resembled the light 
gray bark of cottonwood, sometimes of very light tint and again of 
darker color to agree with surrounding conditions. The dark color of 
cocoon often corresponded with that of the bark deprived of epidermis. 
Some were darkest at the terminal ends, of a chestnut tint, especially 
if spun against the surface of the branch covered by an eschar, always 
of darker shade. Some cocoons on surface exhibited striae, such as seen 
on young branches, here and there speckled, or raised bits of bark to 
mimicry and deceive enemies. In the open I have observed such 
cocoons on small canes of willow, as well as on the roughest bark'of 
great cottonwoods, from which they had to be chiseled out with diffi¬ 
culty. All such yielded similar imagines as those bred. The in¬ 
side of cocoon presented a smooth surface, and a concavity existed in 
the stem where bark was bitten off to receive one-half or one-third of 
the pupa. The sides of cocoon generally flattened, plainly showing 
silken threads, where attached to bark. 
The cocoon is elliptical, mostly rounded, a very few flattened, 
tapering at end like a wedge. One or two cocoons seemed to be more 
ovoid than elliptical in shape. The measurement of another cocoon 
taken from a second observation jar is as follows: Length, 33 mm., 
width, 11 mm.; and height at central area, 6.5 mm. Another smaller 
cocoon gave length, 25 mm.; width, 9.5 mm.; and height, 5.5 mm. 
All larvae of this brood spun their cocoons between November 8th 
and 17th. 
Pupa. Cylindrical, tapering mostly at inferior extremity, where much rounded. 
Toward the head much less reduced in size. The flattened parts of pupa restricted 
to upper two fifths, and on abdomiaal surface extending almost to the end of wing 
cases. Head and antennae case prominent, and that of wings much more on dorsal 
surface. Abdominal segments on dorsal surface thickly covered wi.h fine, dark 
points, as viewed through a lens. Length, 21 mm., breadth, 7 mm at the middle 
part, and 6.5 mm. across thorax. Color of dorsum almost chestnut of lighter tint 
toward anal segment. A longitudinal, dorsal black line from the thorax to penulti¬ 
mate, abdominal joint. Color of case covering palpi, antennse and wings, show 
