OF ARTS AND SCIENCES. 73 



or quite vanished. Of the dorsal ones I can with difficulty, by means 

 of a good lens, find faint traces, they are so nearly effaced.* 



There are in G. angulifera no black spots on the base of the four 

 pairs of middle abdominal legs, and there is a black ring only on the 

 lower side of the anal legs, as in G. promethea. Thesuranal plate bas 

 two transverse linear black spots on the ends, but none of the other 

 black markings of G. promethea. It wants the pair of triangular black 

 sternal spots situated in front of each pair of thoracic legs of G. pro- 

 methea. The median dorsal horn on the 8th abdominal segment is 

 black at the base and tip. The two dorsal black tubercles on the 'Jth 

 segment, and the lateral ones, are wanting, though they are conspicu- 

 ous in G. promethea. 



G. angulifera is much duller in color and much less ornamented, 

 with shorter, less conspicuous tubercles, and all, both dorsal and lateral. 

 on abdominal segments 1 to 7 are wanting. It seems to be a form 

 which may be regarded as having originated later than C. promethea. 

 and which has diverged from it, and it seems to be a species which 

 has directly evolved from the stem-form promethea. 



Recapitulation of the more Salient Ontogenetic Features 



ok Callosamia. 



A. Congenital Features. 



1. Hatched with heavy black transverse bands on a yellow body, 

 and the head black, banded with yellow; the bristles moderately long; 

 thus the larva is already a rather conspicuous object. 



2. The dorsal thoracic tubercles already differentiated in size and 

 color from those on abdominal segments 1 to 7. The differences be- 

 tween the freshly hatched larva and the last stage very marked ; more 

 so than in Platysamia or Samia. 



B. Evolution of later Adasptational Features. 



1. In Stage II. the body becomes paler, and thus the black bands 

 more conspicuous. The 2d and 3d thoracic dorsal tubercles and 

 those on abdominal segments 1 to 8 are now all yellowish, and of the 



same size. 



* These tubercles have evidently disappeared owing to di9use. Wlial there 

 is in its habits to bring this about is a matter of conjecture ; tins form is only 

 known to feed on the tulip tree, and this may be a case of arboreal selection ; 

 the change of food plant, together with possibly the abundance of t I, tin- 

 tree having but few species of larvae feeding on it, may have had something to 

 do with the abolition of the tubercles. 



