274 BRITISH LEPIDOPTERA. 



black. (5) In stage 3 the dorsal tubercles of meso- and metathorax showy coral-red, 

 the subdorsal and infraspiracular tubercles, tipped with pale blue ; in stage 2 the 

 same tubercles are almost entirely pale blue. (6) The head becomes green in stage 



4, with a black spot on the side. (7) The larva is most gaudily coloured and con- 

 spicuous in the last two stages while in S r . cynthia there are not such marked 

 differences between the different stages, though the last is the most variegated, 

 owing to the beautiful turquoise-blue trappings. 



Callosamia (promkthea). — A. Congenital characters'. (1) Hatched with 

 heavy black transverse bands on a yellow body, and the head black-banded with 

 yellow, the bristles moderately long (the larva is thus already rather conspicuous). 

 (2) The dorsal thoracic tubercles already differentiated in size and colour from those 

 on abdominal segments 1 to 7. The differences between the freshly-hatched larva 

 and the last stage, verymaiked (more so than in Platysamia or Samia). B. Evolution 

 of later adaptational characters : (1) In stage 2 the body becomes paler, and shows 

 the black bands more conspicuously. The second and third thoracic dorsal tubercles, 

 and those on abdominal segments 1 — 8, are now all yellowish and of the same size. 

 (2) Disappearance in stage 3 of the transverse black bands. The abdominal 

 tubercles all become blackish. (3) In stage 4 the head becomes yellow, being less 

 conspicuously marked, and the dorsal abdominal tubercles are about half as long and 

 large as those on the meso- and metathorax. (4) The body becomes, in the last 

 stage, much smoother than before, the dorsal prothoracic and abdominal tubercles 

 being much shorter than in stage 4. * 



TELEA ( Polyphemus) f.— A Congenital characters : (1). The setae 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 colour of the dorsal tubercles, 

 those of the third thoracic and 9th abdominal segments being of the same size 

 and larger than those on uromeres 1-7, and of a deeper yellow shade (stage 1). 



(3) The homologue of the caudal horn is distinctly double and more deeply divided 

 than in any other American genus of Attacinae; each fork about as long as thick 

 (stage 1). (4) Abdominal prolegs with 24 crochets a larger number by 6 to 8 than 

 in the other genera (stage 1). (5) Each abdominal segment or uromere with a 

 lateral pair of transverse black slashes in stage 1. (6) The two tubercles in stage I 

 on the suranal plate, slender, papilliform and approximate. £. Evolution of later ad - 

 aptational features : (1) The lateral pair of black transverse stripes on each uromere 

 nearly or quite disappears in stage 2. (2)The segments more convex and angular in stage 

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

 of the lower and upper row in stage 3. (4) Appearance of the pale purplish edging 

 of the suranal plate and anal legs in stage 3. (5) Appearance in stage 4 of the 

 pearly spot on the outside of the dorsal tubercles. \_N.B. — The generic characters 

 are mostly assumed in stage 3.] 



* This reduction of size and iuconspicuousness of the dorsal abdominal 

 tubercles is carried out to excess in Eacles angulifera, where they become obsolete, 

 and the larva is simply a large green caterpillar with inconspicuous markings and 

 simply protected by its green colour like the majority of lepidopterous larva?, 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 are 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, the larva, 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 ol its natural enemies. A tendency to the same end is 

 seen in the larva of S. cynthia, which is paler, less gaily ornamented with 

 bright markings, and also is much less heavily intercolored than the caterpillar of 



5. cecropia. It is evident that of the two species of Callosamia, C. promctliea is the 

 more primitive form and C angulifera a derivation from it. Likewise the Asiatic genus, 

 Samia (S. cynthia being an introduced form), with little doubt, is a form which has 

 undergone more or less modification, &c, indeed, a slight degree of reduction or 

 atrophy, and is thus a later form, the genus Platysimia being an earlier type, since 

 it has been evolved from Saturnia, which is the most primitive genus of the 

 family (Packard). 



t The life-histories of the colossal moths, Telea polyphemus and Actios luna 



are of much interest in connection with the subject under review. It must be 



premised that the shape of tin- tubercles and the glandular seta* they bear differ 



greatly in the freshly-hatched larvae from their appearance after the first moult 



see Proc. Amcr. Acad. A/Is Set., xxviii., p. 80). 



