MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 4t 



3. The tlioracic dorsal tubei'cles deep orange; their homologiies ou the abdominal segments 

 amber yellow. 



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



5. In Stage III the dorsal tubei'cles of second and third thoracic segments showy coral red. 

 The subdorsal and infraspiracular tubercles tipped with pale blue; in Stage II the same tubercles 

 are almost entirely pale blue. 



6. 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 S. 

 vynthia there are not such marked ditterences between the different stages, thongh the last is the 

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



In CaUosamia prnmethea 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 OF THE MORE SALIENT ONTOGENETIC FEATURES OF CALLOSAMIA. 



A. COXGEXITAL FEATCRES. 



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 FEATCRES. 



1. In stage II the body becomes paler, and thus the black b.mds more conspicuous. The 

 second and third tlioracic dorsal tubercles and those on abilominal segments 1 to 8 are now all 

 yellowish and of the same size. 



2. Disappearance in Stage III of the transverse black bands. The abdominal tubercles all 

 become blackish. 



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

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

 segments. 



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

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

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

 become obsolete, and the larva is simply a large green eater-pillar with inconspicuous .markings, 

 and simply protected by its green color, like the majority of lepidopterous larvje, not being so 

 strikingly marked as in the fully fed Samia. cynthia. 



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 

 spines. 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/nthia, which is paler, less gaily 

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

 of Platysamia cccropia. 



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

 C fl«</M/i/Vrrt a derivation from it; the former is what systematists call a "higher" species and 

 C. aiujiili/cra a "lower," but many "lower" species are simply a set of those individuals which 

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



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

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

 atriii)hy, and is thus a later form, the genus Phitymmia being an earlier type, since it has probably 

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



