234 MEMOIRS NATIONAL ACADEMY OF SCIENCES. vol. xii. 



yellow, more distinctly banded with black than before, the two heaviest and broadest bands 

 being on the hinder edges of the prothoracic and the eighth and ninth abdominal segments, 

 while the suranal plate is blacker than before, with a lateral black line. On the other segments, 

 the black bands (two to each segment) are confined to the back, and do not extend down the sides. 

 All the tubercles from the second thoracic to and including the ninth abdominal ones are 

 yellowish. 



At the end of this stage, length 18 mm. The body is rather thicker than before, and whiter 

 yellow; the head with more white, especially on the vertex, and the white stripe across the middle 

 is rather wider. The second and third thoracic, first, eighth, and ninth abdominal dorsal tuber- 

 cles are not distinctly larger than the others, and all are paler. The black stripes are nearly 

 as before, but perhaps not quite so heavy. The suranal plate is not so black as before, but with 

 two black spots; and on the side of the anal plate is a black elongated patch. 



Stage IV: Length 34-35 mm. The characters of the fully grown larva are now nearly 

 attained. The head is large, three-fourths as wide as the body, pale lemon-greenish, with six 

 black dots, two below, and one above. The two dorsal prothoracic tubercles yellowish; the 

 lateral ones black. The two dorsal tubercles on the second and third thoracic segments are now 

 high, large, and with obsolete spines, red, with a black base or ring (Miss Soule says, "black at 

 base, ringed with yellow, orange at tips, smooth")- The single one on the eighth abdominal 

 segment is ringed with black at the base, and beyond yellow ; it is slightly smaller than those on the 

 thoracic segments. All the other dorsal as well as lateral tubercles are now reduced to low small 

 black rudimentary tubercles. In this stage it differs from that of C. promethea of the same stage in 

 the much shorter black tubercles on the second to seventh abdominal segments; and in the dorsal 

 tubercles on the second and third thoracic segments being reddish, instead of yellowish. The 

 curved horseshoe-shaped black line on the side of the anal legs is the same as in C. promethea. 

 The "yellow stigmatal ridge" noticed by Miss Soule is shown in Bridgham's figure. 



Full-grown larva. — Length 68 mm. On comparing a blown specimen of C. angulifera with 

 one of C. promethea the former differs in the following particulars. The head is slightly larger, 

 without the two black dots in front and the lateral dot, and without the broad black stripe 

 extending hi C. promethea from each side of the base of the labrum upward, and ending on the 

 side of the head below the lateral dot. The four dorsal black spots on the prothoracic segment 

 are wanting in C. angulifera, and the short lateral tubercles are not colored black as ha C. pro- 

 methea, while the tubercles themselves are much smaller and less prominent. The four dorsal 

 tubercles (two on the second and two on the third thoracic segment) are decidedly smaller and 

 slenderer than in C. promethea; the tips are black where those of C. promethea are yellow, and 

 the black ring around the base is narrower than in C. promethea. The two lateral small black 

 tubercles on each of these segments are wanting, and all traces of them have nearly 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. 1 



There are in C. 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 hi C. promethea. The 

 suranal plate has two transverse linear black spots on the ends, but none of the other black mark- 

 ings of 0. promethea. It wants the pah of triangular black sternal spots situated in front of 

 each pair of thoracic legs of C. promethea. The median dorsal horn on the eighth abdominal 

 segment is black at the base and tip. The two dorsal black tubercles on the ninth segment, 

 and the lateral ones, are wanting, though they are conspicuous in C. promethea. 



C. 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. 



1 These tubercles have evidently disappeared owing to disuse. What there is in its habits to bring this about is a matter of conjecture; this 

 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 abun- 

 dance of food, this tree having but few species of larvae feed big on it, may have had something to do with the abolition of the tubercles. 



