1890.] 
511 
[Packard . 
be seen that not only are there different adaptive characters in the 
larval, pupal and imaginal stages, but that the larva itself in its 
different stages is wonderfully adapted to different surroundings. 
1. At first some, indeed most, species live socially on the under 
side of the leaves, near where they were born, and thus concealed 
from observation. Many have glandular hairs, while the tubercles 
are more or less uniform. 
2. Toward the end of Stage II, and in Stage III, they feed in ex- 
posed situations on the upper side of the leaves, and at the same 
time appears the showy style of ornamentation both as regards 
colors, hairs and tubercles, approximating to that of the mature cat- 
erpillar, whose life apparently is conditioned by its bright colors 
and bizarre trappings. 
The smooth-bodied, green larvae of Nadata and Lophodonta, etc., 
are the primary forms. Their shape, coloration and retired habits 
ally them biologically to the larvae of the European Panolis pini- 
perda , and other smooth-bodied, green caterpillars with reddish or 
yellowish stripes, which feed on trees. These smooth larvae are how- 
ever, rare and exceptional. 
But now owing to a change in the environment, there arose a ten- 
dency to the hypertrophy of the normal piliferous warts, and in the 
actual life-history of the caterpillar the tendency manifests itself 
in the third stage of larval life. We are inclined to believe (1) 
that the hypertrophy of certain of the tubercles was effected in a 
comparatively sudden period, in consequence of a comparatively 
sudden change from herbs to trees, and (2) in response to a sudden 
exigency ; (3) that the spines and stiff, dense spinulated hairs were 
immediately useful in preventing the attacks of parasitic insects, 
while (4) the poison-glands at the base of the tubercles (in the At- 
taci, etc.) served to render them distasteful to birds ; (5) the bright 
colors serving as danger-signals. 
The Lamarckian factors (1) of change (both direct and indirect) 
in the milieu , (2) need, and (3) habit, and the now generally adopted 
principle that a change of function induces change in organs 1 and 
in some or many cases actually induces the hypertrophy and spe- 
cialization of what otherwise would be indifferent parts or organs ; 
1 R. Marey : Le transformisme etla physiologie exp^rimentale, Cours du College de 
France. Revue scientifique, 2d Serie, IV, 818. (Function makes the organ, especially in 
the osseous and muscular systems.) 
See also A. Dohrn : Der Ursprung der Wirbelthiere und das Princip des Functions- 
wechsels, Leipzig, 1875. 
