78 PROCEEDINGS OF THE AMERICAN ACADEMY 



Recapitulation of the more Salient Ontogenetic Features. 



A. Congenital Features. 



1. Hatched with large, well developed setiferous tubercles; but the 

 bristles not bulbous in Stage I. 



2. The body pale, but the tubercles dark, and besides these inter- 

 tubercular conspicuous black spots are present in Stages I. to V. 



3. The hornologue of the "caudal horn" is double, bearing foui 

 bristles on each side. 



The difference between the larva of the first stage and the last, un- 

 usually slight compared with Platysamia and Callosamia. 



B. Evolution of later Adaptational Features. 



1. The tubercles become pale at tip in Stage III., and those of 

 the two dorsal rows of the thoracic and last two abdominal segments 

 become slightly larger than those of abdominal segments 1 to 7, in 

 Stage III. 



2. Differences in coloration appear in Stage IV., the head, protho- 

 racic and last two abdominal segments being honey-yellow, thus con- 

 trasting with the whitish body, with its whitish bloom, which also 

 appears in this stage. 



3. Farther changes in color appear in the last stage, the ends of 

 all the tubercles becoming pale bluish, and the edges of the suranal 

 plate and anal legs being a rich turquoise-blue. 



4. In the last stage a very slight difference in the size and shape 

 of the thoracic and the last abdominal tubercle. 



5. The tubercles on the suranal plate become reduced to low bosses, 

 without bristles. Thus Samia cynthia is a decided step in advance 

 of Platysamia, and appears to be a later formed genus. 



Comparison between the Larva of Samia and Callosamia. — The 

 fully fed larva of Samia cynthia is in the shape of the head and 

 body, and in the shape of the tubercles with which the latter is 

 armed, more allied to Callosamia than to Attacus, although the imago 

 is perhaps as near the latter genus as to Callosamia. The head of 

 the larva of Samia is almost identical with that of Callosamia. The 

 nearly obsolescent tubercles on the prothoracic segment have about the 

 same degree of degeneration in Samia as in Callosamia, but the former 

 differs in the fact that the lateral tubercles in all three thoracic seg- 

 ments are well developed, and end in a head armed with four spines, 

 as in Platysamia (P. cecropia), while the tubercles are as well de- 



