42 MEiMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



The terms "high" iiud "low" are expressions mucli misused and misai)])lied; tlie terms 

 generalized, or early or primitive; and modified, specialized, or later, are perhaps truer to nature. 



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

 the ancestral forms. For example, the Diptera, especially the Muscid;e, are the most modified of 

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

 uoptera, especially the wasi)s 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 moths, Telca polfiphcnius and Actian I una, are of nnich interest 

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

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

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

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



RECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF TELEA POLYPHEMUS. 



A. COXGENITAI, FICATUUES. 



1. The setfB (bristles) of Stage I but little longer than the tubercles, and both truncate and 

 distinctly bulbous at tip. 



2. A slight but distinct differentiation in size and 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 than in 

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



4. 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. 



C. The two tubercles in Stage I on the suraual plate slender, papilliform, and approximate. 



B. EVOLUTION OF LATER ADAPTATION'AL 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 suraual ])late and anal legs in Stage III. 



5. Appearance in Stage IV of the pearly spot on the outside 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. Setie 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 larvse iu 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 in front is twice banded with dark 

 brown. 



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

 larger than the abdominal ones. 



4. On the suraual ])late 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 1 of G, promelhea or T. pohjphemm, but it is more duplex than in P. cecropia. 



1 See Proc. Amer. Acad. Arts and Sciences. Boston, xsviii, p. 80. 1893. 



