238 MEMOIRS NATIONAL ACADEMY OF SCIENCES. vol. xii, 



steel-blue minute tubercle, this being the fourth on each side. Abdominal legs dark, with a 

 yellow spot at the base on the outside. 



Stage III: Described May 29. Length 35 mm. The larva is in this stage a very different 

 creature from what it was in the previous stages. It is now gorgeously colored, and a very con- 

 spicuous caterpillar. The ground color of the body is pea-green, while the large swollen base 

 of each tubercle is deep reddish orange approaching vermilion, contrasting with the dark steel- 

 blue of the spines surmounting the base. 



The head is very small, not one-half as wide as the body, and one-third narrower than 

 the first thoracic segment. The clypeus-posterior is now pale turquoise-blue, and there is a 

 broad red-orange stripe on each side of the clypeus. 



The tliree black spots on each segment are still large and conspicuous, wliile those on the 

 hinder edge are minute. The center of the suranal plate and of the anal legs is stained deep 

 red-orange, as also the outside of the mid-abdominal legs. The thoracic legs are also painted 

 with two vermilion-red rings. 



There is the same proportion between the size of the dorsal tubereles. 



The seta? are scarcely as long as the spines themselves. 



Stage TV: Length 38-40 mm. Differs but little from the previous stage hi armature and 

 coloration. In this stage most of the larvae have the tubercles entirely black; in a few, how- 

 ever, the dorsal ones on the second and third thoracic, first, second, third, and eighth and ninth 

 abdominal segments are pale blue at the tips; and sometimes those on a less number of segments 

 are tipped with blue. The six tubercles on the prothoracic segments are still well developed. 

 The suranal plate is pale red; the sides of the anal legs deep bright red, as also are the ends of 

 the mid-abdominal legs; the thoracic legs are black ringed with red. 



Stage V: Length 65-70 mm. Head and body pea-green. Shape of the body nearly as 

 in PMlosamia, but the tubercles very much thicker and larger. Those on the third thoracic 

 segment and first abdominal a little larger than the pair on the second thoracic segment. The 

 dorsal abdominal tubercles somewhat unequal in size, those on segments 2-7 about one-half 

 smaller than those on the first abdominal segment, those on segment six being a little smaller 

 than the others. The median tubercle on the eighth abdominal segment nearly tliree times 

 as thick as that on the sixth segment. All the tubercles bright red on the swollen base; be- 

 yond, turquoise-blue; the short spinules black. Suranal plate, the side of the anal legs, and 

 the thoracic legs yellow. Mid-abdominal legs yellow, black at base. 



There are two subdorsal rows of black spots, one on each side; a black band on the front 

 of each segment passes down to a point near the spiracles. The larvae vary hi the amount of 

 black on the body, some having more, others less. 



The larva differs from stage TV hi the part of the tubercles above the red swollen base 

 being much thicker, the spinules shorter, and there are no tubercles on the prothoracic seg- 

 ment, these being in the last stage represented by black dots. 



The larva feeds on the wild cherry. 



This is an unusually conspicuous larva, and as usual in the group the bright hues and spots 

 may be regarded as warning colors, the insect behig protected by what are probably venomous 

 spines. 



In its markings (the six dorsal black spots) and armature it closely resembles PMlosamia 

 cynthia; the tubercles are all large and of nearly equal size and shape as in the second stage of P. 

 cyntltia. There is no such inequality as is to be observed in the third stage of C. promethea, 

 where the second and third thoracic dorsal tubercles and that in the middle of the eighth 

 abdominal segment are tliree times as large as all the other dorsal abdominal ones. 



Judging by the larval characters PMlosamia cynthia is a more primitive or generalized 

 form than C'allosamia, since PMlosamia retains the equality in the size and shape of the tubercles 

 all through its larval life. 



C. calleta up to the end of stage III is really nearer to PMlosamia than the genus to which 

 it is generally referred, and this suggests that phylogenetically PMlosamia is the older genus, 

 and that from it directly sprang the species of Callosamia, C. calleta being the oldest species. 



