MEMOIRS OP THE NATIONAL ACADEMY OP SCIENCES. 41 



3. The thoracic dorsal tubercles deep orange; their lioiiK)h),nues on the abdoiuiiuil segments, 

 amber yellow. 



4. The tubercles at the end of Stage 11 and in Stage III spotted on the sides with black. ^ 



5. In Stage III the donsal tubercles of second and third thoracic segments showy coral red. 

 The subdorsal and infrasi>iraeular tubercles tipped with pale blue; in Stage II the same tubercles 

 aie almost entirely pale blue. 



G. The head becomes green in Stage IV, with a black spot on the side. 



7. The larva is most gaudily colored and conspicuous in the last two stages, while in »SV 

 cynfhia there are not such marked differences between the different stages, though the last is the 

 most variegated, owing to the beautiful turquoise-blue trappings. 



In Callosamia lyromethea the freshly hatched caterpillar is most remarkably banded, and all its 

 marks and tubercles are in striking contrast with the fully grown larva. The differences may be 

 epitomized as follows : 



RECAPITULATION OP THE MORE SALIENT ONTOGENETIC FEATURES OP CALLOSAMIA. 



A. CONGENITAL FEATLBES. 



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 abdom- 

 inal segments 1 to 7. The differences between the freshly hatched larva and the last stage very 

 marked; more so than in Platysamia or Samia. 



B. EVOLUTION OF LATER ADAPTATIONAL FEATURES. 



1. In Stage II the body becomes paler, and thus the black bauds more conspicuous. The 

 second and third thoracic dorsal tubercles and those on abdominal segments 1 to 8 are now all 

 yellowish and of the same size. 



3. Disappearance in Stage III of the transverse black bauds. The abdominal tubercles all 

 become blackish. 



3. In Stage IV the head becomes yellow, being less conspicuously marked, and the dorsal 

 abdominal tubercles are about half as long and large as those on the second and third thoracic 

 segments. 



4. The body becomes in the last stage much smoother than before, the dorsal prothoracic and 

 abdominal tubercles being much shorter than in Stage IV. .This reduction of size and iuconspieu- 

 ousness of the dorsal abdominal tubercles is carried out to excess in G. aiKjuli/era, where they 

 become obsolete, and the larva is simply a large green caterpillar with inconspicuous .markings, 

 and simi)ly protected by its green color, like the majority of lepidopterous larvie, not being so 

 strikingly marked as in the fully ted Samia cijiithia. 



It is not improbable that the reduction and atrophy of the dorsal tubercles in question is also 

 accompanied by a great reduction, if not total abolition, of the poison glands at the base of these 

 si)ines. However, having lost the power of resisting or avoiding attack by this means, it, by the 

 action of the law of correlation, also loses its bright markings or danger signals, and having 

 become harmless to its enemies it is preserved from.extinction by passively relying on its smooth, 

 glaucous-green body to escape the observation of its natural enemies. 



A tendency to the same end is seen in the larva of Samia ci/iithia, which is paler, less gaily 

 ornamented with bright markings, and also is much less heavily intercalated than the caterpillar 

 of Platysamia cecrojna. 



It is evident that of the two species of Callosamia, C. promethea is the more primitive form and 

 C anf/H/i/fm a derivation from it; the former is what systematists call a '-higher" species and 

 C. anguUfera a -'lower," but many "lower" species are simply a set of those individuals which, 

 have undergone some degree of modification or degeneration, and are later in point of origin. 



Likewise the Asiatic genus, Samia (S. cyuthia being an introduced form), with little doubt, is 

 a form which has undergone more or less modiflcation and indeed a slight degree of reduction or 

 atrophy, and is thus a later form, the genus Platysamia being an earlier type, since it has probably- 

 been envolved from Satuniia, which is the most primitive genus of the family. 



