42 MEMOIES OF THE I^ATIOXAL ACADEMY OF SCIENCES. 



The terms "high" and "low" are expressions much misused and misap])lied; the terms 

 generalized, or early or primitive; and modified, specialized, or later, are i)erhaps truer to nature. 



It is not always the highest — i. e., most specialized— forms which are furthest removed from 



"the ancestral forms. For example, the Diptera, especially the MuscidiB, are the most modified of 



insects, i. e., the furthest removed structurally from the winged ancestral forms; but the Hyme- 



noptera, especially the wasps and bees, when we take into account the adult stage, are the 



"highest" — i. e.. the most specialized — of all insects. 



The life histories of the colossal niotbs, Telea poJyphemusi and Actias luna, are of much interest 

 in connection with this topic, and our remarks should be illustrated by elaborate detailed descrip- 

 tions and colored figures, but the essential points maybe indicated by the following epitomes. It 

 should be premised that the shape of the tubercles and the glandular setie they bear differ greatly 

 in the freshlj' hatched larva from their appearance after the first molt:' 



RECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF TELEA POLYPHEMUS. 



A. CliXGENITAL FEATUUES. 



1. The setiTP (bristles) of Stage I but little longer thau the tubercles, and both trnucate and 

 distinctly bulbous at tip. 



2. A slight but distinct differentiation in size aiul color of the dorsal tubercles, those of the 

 third thoracic and ninth abdominal segments being of the same size, and larger than those on 

 uromeres 1-7, and of a deeper yellow shade. (Stage I.) 



3. The homologue of the "caudal horn" is distinctly double and more deeply divided tlnin in 

 any other American genera of Attacina?; each fork about as long as thick. (Stage I.) 



i. Abdominal legs each with 24 crotchets — a larger number by to 8 than in the other genera. 

 (Stage I.) 



5. Each abdominal segment (uromere) with a lateral pair of transverse black slashes in 

 Stage I. 



G. The two tubercles in Stage I on the suranal plate slender, papilliform, and approximate. 



B. EVOLUTION OF LATER ADAPTATIOXAL CHARACTERS. 



1. The lateral pair of black transverse stripes on each, uromere nearly or quite disappear in 

 Stage II. 



2. The segments more convex and angular in Stage III. 



3. Appearance of a yellowish lateral oblique stripe connecting the lateral tubercles of the 

 lower and upper row in Stage III. 



4. Appearance of the pale purplish edging of the suranal plate and anal legs in Stage III. 



5. Appearance in Stage IV of the pearly spot on the o.utside of the dorsal tubercles. 

 The generic characters are mostly assumed in Stage III. 



RECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF ACTIAS LUNA. 



A. CONGENITAL FEATURES. 



1. Set» tapering to a point, not bulbous, and finely barbed. (Stage I.) Most of them are 

 three or four times as long as the tubercles. 



2. Some larvi¥, in Stage I with a very broad lateral dark band along the side of the body, 

 some without it; no transverse stripes present, but the head iu front is twice banded with dark 

 brown. 



3. The second and third dorsal thoracic tubercles differentiated iu Stage I, being slightly 

 larger than the abdominal ones. 



4. On the suranal plate are two rudimentary tubercles, each bearing a tuft of bristles. 



5. The dorsal median tubercle on uromere 8 does not show such marked traces of its double 

 origin as Stage I of G. promethea or T. polyphemus, but it is more duplex than iu P. cecropia. 



' See Proc. Amer. Acad. Arts aud Sciences. Boston, xxviii, p. 80. 1893. 



