ME]\I01ES OF THE KATIOKAL ACADEMY OF SCIE^TCES. 
37 
^Tow, it seems natural to supi>ose that the disappearance of the armature of this insect with 
the first molt was due to the lack of need for it by the caterpillar, which gradually became adapted 
to a life on the underside of an oak leaf, where it assumed a simple spindle-shaped body extended 
when at rest along the midrib, in which position wo liave found the older caterpillar, its body 
glaucous-green and so marked with yellowish lines and reddish spots, as well as with daslies and 
lines, as to be wonderfully assimilated to the greenish, reddish, and whitish hues of the leaf under 
which it was sheltered. 
rio, 1.— Early btagos of Heterocamna obliqva and H. guttivitta.—l. JfJeUrocampa obliqua Pack Ereebly batched larvaj Jcr, dorsal 
■view; lli, spine on third; le, spine ou eighth; Id, spine on ninth abdominal segment; Jr.prothoracic horns of stage I, enlarged. IT. Hetero- 
campa obliqua Pack . — Stage IT; 2 la, horns on first prothoracic segment. III. Peterocampa guttivitia TTaZ*. — Horns in stage 1; a, pro- 
thoracic horn ; 6, one on second abdominal; c, one on third to fifth, and d, on ninth abdominal segment. (Thesetas are in some cases omitted). 
It also seems reasonable to supi>ose that these adaptational, colorational features were acquired 
by the ancestors of the present forms during the dilfereut stages succeeding the first ecdysis. 
And thus we are warranted in assuming that this and multitudes of other cases of adaptation to 
the change in habits and modes of life and special situations were acquired originally, at different 
periods after birth, during an earlier geological iieriod than this, when the ancestors were fewer 
in number and more plastic than now. Otherwise, how can we have the differentiation of a few 
