THE COLORATION OF BUTTERFLY LARVAE. 69 



extraordinary diversity in the same caterpillars when fullgrown. 

 Some alter very much less than others, some assume the mature 

 aspect by slow degrees, others suddenly, and at very different periods 

 of larval life, e.g., the mature form may be said to be assumed in the 

 second stage by Laertias (philenor) and Iphiclides (ajax), at the fourth 

 by Heraclides {cresphontes) and Papilio (polyxenes), in the course of the 

 fourth by Jasoniades (glaucus), and not until the final stage by 

 Euphoeades (troilus). The assumption of maturity is shown by several 

 distinct features, which, in general, are correlated — the form of the 

 body, the broad features of the colouring of the body, and the loss of 

 the juvenile armature. In only one instance, viz., the larvae of the 

 species belonging to Papilio, are the tubercles retained (and here only for 

 a single stage) after the adult form and markings have appeared, and, 

 excepting Laertias, where the markings are almost null through life, 

 Heraclides is the only example where the ornamentation of the body of 

 the adult in any way resembles that of the newly- born caterpillar." 

 As a general conclusion, Scudder assumes that " the ancestral 

 Papilionid larva was covered with rows of fleshy, mammiform 

 tubercles, beset with bristles, and that these were retained through 

 life ; but that, in the gradual development of the group, they were 

 lost, first at the final stage, as we now find it in Papilio, afterwards at 

 successively earlier and earlier stages ; the loss consisting, first in the 

 removal of the bristles, afterwards in the lowering of the tubercles until 

 only smooth and shining lenticles remained, as now exhibited in the full- 

 grown caterpillar of Heraclides ; these again, in several genera, were 

 replaced by coloured spots, some of which, e.g., Euphoeades and 

 Jasoniades, assumed special forms. It may further be presumed 

 that the early larva was dark in colour, probably of an uniform dark 

 colour, with a tendency towards a deepening of the tint of the region 

 about the 3rd thoracic segment (which only assumes a special import- 

 ance in these larvae), and also about the 7th abdominal segment, by 

 the tendency of both markings and dermal appendages to assume a 

 polar arrangement in elongated forms. By this means, and through 

 the intensification of these contrasts, arose the lightening of the 

 middle parts of the body to form a saddle-shaped whitish patch — a 

 marking surely of great antiquity in swallow-tail larvae, since it is now 

 found at birth in four of the six genera found in North America, and 

 a fifth shows a tendency towards it. This style of marking has been 

 retained throughout life in Heraclides only, of all the members of the 

 Nearctic fauna ; and, as it is in just this genus alone that the lenticle 

 traces of the tubercles persist to maturity, we have certainly in 

 Heraclides the perpetuation of a very antiquated type. That, in Papilio, 

 we also have a very persistent type, may be judged from the great 

 stability of the upper tubercles, which are even now not lost until after 

 the assumption of the changed livery of maturity, a livery which owes a 

 part of its variety and enlivenment to exchange of some of these 

 tubercles for bright-coloured spots ; these break up the transverse 

 black stripes in a variable degree, and the stripes themselves appear to 

 be but little more than retention of parts of the original colour (freed 

 at the particular spots they occupy by the central position of the black 

 tubercles), when the green livery of adult life is assumed, for it seems 

 to be a green resembling the green of the leaves upon which the larva 

 lives, that is, the ultimate aim of most Papilionid coloration. In 



