26 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Ill the fiiU-fi'd liirvu of C. Stpuhralis there are no detinite .stripes, the ohli(|iie ones are not 

 present. 



In C. regalh, espeeiallv, tlie olili(|ue, lilack stripes are eontiiuied iiy tlie laryv conspicuous 

 black spiracles, and also hy the black stripe on the outside of the niid-abdoininal legs. Thus the 

 efl'eet of the stripes themselves is heightened and e.\tended by these supplementary markings 

 situated in line with l)ut l)elo\v the o))lique stripes. 



In stage IV the oblique stripes are more diHuse. broader, and reach so as to almost include 

 the spiracles, which are as large as in stage V and last, and from each spiracle a black stripe 

 descends obliquely to just behind each infraspiracular spine, and then blends with the black 

 stripe on the mid-abdominal legs, though there is no corresponding stripe on the other legless 

 al)dominal segments. It is also to be observed that the blackish ol)lique stripes are confined to 

 a single segment, not passing on to the next one, and an oblique anteroposterior stripe extend- 

 ing from the front edge of the segment down to the spiracle is the reverse of what obtains in 

 the majority of the Sphingidse. 



In stage V, C regal is (in a dried, l>lown example) is rather less blackish than in stage IV, 

 and under each blackish stripe is a pale shade. The spines are also much smaller, so thjit the 

 larva is less black; the light shade is a little wider than the black band itself. 



Another set of black markings is the great dorsal black patches on the second and third 

 thoracic segments of stages III to V. and the narrow cross-liand between the third thoracic and 

 first abdominal segments; their signilicance may be cleared up by observations on the living- 

 insect. 



VI. DICHROMATISM OR COLOR VARIATION IN THE LARVA. 



The best-known case of dichromatism in larvie is that of Thyrtus ahhotii^ described by 

 Kiley, in which there is a dark brown and a green form. Lieutenant-Colonel Fawcett describes 

 a dark form of the larva of Protoparce inauritii, of Natal, while Aeliemntia atropos is said by 

 Trimen to have a dark form at Cape Town. Light and dark color varieties have been artilicially 

 produced by Prof. E. B. Poulton. Mr. ^leldola had previously (Proc. Zool. See, London, 

 p. 155, 1873) called attention to the fact that the 3'ounger larvaj of Geometra papillonaria are 

 brown, "and remain brown during hibernation, when the leaves are bare, while man}* of them 

 become green when older, after the leaves have expanded in spring." Mr. Poulton also 

 discovered that '"the younger larvse possess the power of adjusting the shade of their brown 

 color to that of the twigs of their food plant." Mr. ]Meldola calls this [)henomenon "seasonal 

 adaptation," and besides the species mentioned he cites Aciihdia dcgnnenirla, and (jnophos oh^ai- 

 ratii, adding, "and many more could t)e named."" 



In Eaclen iinperialts there are two color forms, i. e., a normal green and a brown form. 

 The}' do not, however, seem to be phytophagic varieties, as both occur on the white pine. 



While the caterpillars in the early stages are usnall_y a light yellowish or cla\- brown, in the 

 fourth and last stages they vary in being either pale green or reddish brown. As these cater- 

 pillars arc not common, it is not easy to state the proportion of brown to green individuals. 

 From what I have seen, I should suppose that the green in the two final stages were the normal 

 or more connnon, and the brown wore more of the nature of aberrations. 



Ml-. Bridgham has, more commonly, found the pale green form on the white pine at 

 Providence, though the brown form occurred on the same tree. 



I will describe the color forms in my possession: 



The green form — Sfngc IV. — The bodj- of a blown example is pale green; the hairs very 

 long, white, and rather thick; the head is pale ocherous, paler than in the reddish brown blown 

 specimen, and of the .same hue as the thoracic legs. The thoracic horns and other spines are 



" ileldola also states that the larv;e of Emmrlcxlii. unifnscifila feod on the seeds of a species of Bartsia when the 

 capsules are in various stages of growth, "and those caterpillars found on the green capsules were green, whilst those 

 on the brown capsules were of a corresponding colour." (Trans, of VVeisniann's "Studies in the theory of descent," 



:., p. :ju7, ISS2.) 



