MEMOTES OF THE NATIONAL ACADEMY OF SCIEISTCES. 
39 
3, Tbe double ])iliferous tubercle on tbe ninth uromere becoming obsolete in Stages lY and Y. 
4. Tbe abdominal region is longitudinally striped with dark and whitish bands, but thei'e are 
no transverse marks in Stage I or in later stages. 
B. EVOLUTION OF LATER ADAPTATIONAL CHARACTERS. 
1. The head slightly angular, face subtriangular, with a light-brown or greenish lateral stripe 
{Stages II-Y). 
2. Ai)pearance of a transverse row of dorsal granulations on the hinder end of each segment 
in Stage II, persisting through larval life. 
3. The eight thoracic spines lose their bulbous tips and become simply slightly forked in Stage 
III and later. 
4. The two dorsal vspines of uromeres 1-7 are in Stage IT larger than the others; in Stage III 
they become ivory white externally and in Stage lY larger and silvery white on the outside. 
5. In the last two stages the eight thoracic spines become very much shorter in proportion to 
the size of the body and become less movable; as they decline in size and functional importance, 
the metallic, silvery, dorsal spines on the abdominal segments become conspicuous and apparently 
useful to the larva. 
The following summary of a better-known caterpillar, that of Eacles imperialk^ will bring out 
more clearly, i)erhaps, the point we wish to make, i. e., that the later adaptational characters have 
been acquired during the lifetime of either one or of a series of ancestral forms leading up to the 
present one. 
•« 
SUmiAUY OF THE CHIEF ONTOGENETIC FEATURES OF EAGLES mPERIALIS, 
A. CONGENITAL CHARACTERS. 
1. In Stage I there are three pairs of very long dorsal deeply forked thoracic horns, nearly 
half as long as the body, 
2. A similar median spine on the eighth abdominal segment, with one half as long on the ninth. 
3. The abdominal segments are transversely banded with black. 
4. The lateral spines on the abdominal segments bifid and nearly as large as the subsimple 
dorsal ones. 
5. Body pale chestnut brown; head light reddish. 
6. The spiracles minute and difficult to detect, as they are situated in one of the transverse 
black bauds. 
B. EVOLUTION OF LATER ADAPTATIONAL CHARACTERS. 
1. The forks of the larger dorsal spines disappear at the end of Stage III. 
2. The dorsal thoracic spines become recurved in Stage III. 
3. The dorsal thoracic and caudal horn become much shorter and stouter in Stage lY, when 
the characters of Stage Y (and last) are nearly assumed. 
4. In Stage II the dorsal spines on the prothoracic segment begin to grow shorter and stouter. 
5. In Stage II the large horns begin to be less deeply forked. 
6. The transverse black stripes disappear at the end of Stage II. 
7. The dorsal and lateral spines on abdominal segments 1-7 are much smaller in proportion 
in Stage III than in Stage II. 
8. Toward the end of Stage III the colors of the body become more conspicuous and variable. 
0. In Stage III the spiracles become parti-colored and very conspicuous. 
10. The dorsal thoracic and the '^caudal horn” become much shorter iu Stage lY and not 
forked at the tip. 
11. The hairs become long and abundant in Stage lY. 
12. The body in Stage lY becomes much stouter and heavier than before, while the head has 
not greatly gained in size iiroportionately. 
The European Aglia tau appears to be the sole representative iu the Old World of the 
American group or family Ceratocampidm, though with the larval, pupal, and imaginal characters 
