MEMIORS OF THE NATIONAL ACADEMY OF SCIENCES. 35 



recapitulated the congeuital characters, and tiiially given a synopsis of the chief stei)s in tlie 

 evohition of tlie adaptional characters, which ai)i)ear after the first exuviation. It seems very 

 probable that these later features were the result of the action of external stimuli, both physical 

 and biological, and that they were acijuired not only during the lifetime of the larva, but at certain 

 distinct stages or periods during the growth of the creature. The changes are both colorational 

 and structural, and during the (lifferent stages the larva was adapted tor different surroundings^ 

 and thus at each important stage was virtually for the time being a distinct animal. 



During the pupa stage special and unusual structural adaptations arose, the cremaster being 

 unusualh' developed, and also a pair of cephalic hooks, seeming to entangle the head in the web 

 of the cocoon, so that the pupa can not be thrown out of the curled leaf, which remains in the first 

 brood on the trees. These I regard as characters acquired by the insect after birth and in response 

 to the exigencies of life at different stages. I will here add the conclusions given in that paper. 



KECAPITrLATION OF THE SALIENT FEATURES IN THE ONTOGENY OF DREPANA ARCUATA. 



A. CONGENITAL CHARACTERS UF TIIK LARVA. 



1. Anal legs obsolete; suranal plate already ending in au elevated rod-like spine in Stage I. 



2. Glandular hairs (split at the end) present only in Stage I. 



3. Piliferous warts well developed but of uniform size on all the segments in Stage I. 



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, forming 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. 



B. EVOLUTION OF LATER ADAPTATIONAL CUAKACTERS. 



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 regior, 

 previously dark, becomes broken up into pale yellowish-green spots. Head distinctly banded 

 with yellow. 



3. In Stages IV and V the greenish portions of the body become 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 degeuerate, and those of the two succeeding 

 stages slightly progress in development. 



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 adax>tational features are: (1) colorational, to enable the partly or fully grown 

 caterpillar to escape observation, and (2) structural, the unusually large ninth and tenth abdom- 

 inal segments being upraised, with the upturned threatening suranal rodorspiue fitted to frighten 

 away ichneumons or Tachin;e, and possibly insectivorous birds. 



C. A SPECIAL ADAPTATION IN THE PVPA. 



The pair of cephalic stout hooks serving to entangle the head in the Web of the cocoon, the 

 cremaster also being unusually well developed, so that the pupa, which in the first brood remains 

 on the tree, is slung by its head and tail, and can not be thrown out of the curled leaf. 



I). PROTECTIVE COLORATION OF THE JIOTII. 



When I first noticed the moths, with their broad wings outspread and resting on the upper side 

 of the leaves, I mistook them for pieces of dead, dry, yellowish leaves which had fallen upon and 

 become fastened to the surface of the fresh leaf. 



