1890 .] 
489 
[Packard. 
4. Head and body dark-brown, but the warts pale ; uromeres 1 
and 7, pale-yellowish, in stage I. 
5. Crochets of abdominal legs more numerous than usual, form- 
ing an incomplete circle, compensating for the lack of anal legs 
and crochets. 
6. These congenital characters are of generic value, the specific 
characters appearing at and after stage III. 
4 
B. Evolution of later adaptational characters . 
1. Reduction in size and length of hairs after stage I, glandular 
hairs being replaced by ordinary, tapering ones. 
2. At the beginning of stage III, the body becomes yellowish- 
green, and the dorsal region, previously dark, becomes broken up 
into pale yellowish-green spots. Head distinctly banded with yel- 
low. 
3. In stages IV and V the greenish portions of the body be- 
come darker, like that of the food plant, and the reddish-brown 
parts are assimilated to the hue of the leaf stalks and twigs. 
4. In stage III, the prothoracic dorsal warts degenerate, and 
those of the two succeeding stages slightly progress in develop- 
ment. 
5. The ninth uromere becomes as large as if not slightly larger 
than the eighth, and separated by a distinct suture from the tenth, 
a very unusual feature in caterpillars. 
6. The chief adaptational features are: (1) colorational, to en- 
able the partly or fully-grown caterpillar to escape observation ; 
and (2) structural, the unusually large ninth and tenth abdominal 
segments, being upraised, with the upturned threatening suranal 
rod or spine fitted to frighten away ichneumons or tachinae, and 
possibly insectivorous birds. 
C. A special adaptation in the pupa. 
The pair of cephalic stout hooks serving to entangle the head in 
the web of the cocoon, the cremaster also being unusually well de- 
veloped, so that the pupa is slung head and tail and cannot be 
thrown out of the curled leaf which in the first brood remains on 
the tree. 
D. Protective coloration of the moth. 
When I first noticed the moths with their broad wings outspread 
and resting on the upper side of the leaves, I mistook them for 
