“A most beautiful illustration of the want of ‘phyletic parallelism,’ as Weismann designates the different form-relationships of the larvæ, pupæ, and imagines, is furnished by the five genera Acræa, Heliconius, Eueides, Colænis, and Dione (= Agraulis). This instance seems to me to be of especial value, because it offers the rare case of pupæ showing greater differences than the larvæ and imagines.
“The species of which I observed the larvæ and pupæ are Acræa Thalia and Alalia, Heliconius Eucrate, Eueides Isabella, Colænis Dido and Julia, Dione Vanillæ and Juno; besides these I noticed the pupa of Eueides Aliphera.
“The following remarks apply only to these species, although we may suppose with great probability that the whole of the congeneric forms—excepting perhaps the widely ranging species of Acræa—would display similar characters to their Brazilian representatives.
“The imagines of the five genera mentioned form two sharply defined families, the Acræidæ and the butterflies of the Maracujá group.[223] The latter comprises the three genera Heliconius, Eueides, and Colænis, which differ only in very unimportant characters; Eueides is distinguished from Heliconius by its shorter antennæ, and Colænis differs from Eueides in having the discoidal cell of the hind-wings open. The genus Dione is further removed by the different structure of the legs, and the silvery spots on the underside of the wings. Certain species resemble those of other genera in a most striking manner, and much more closely both in colour and marking, and even in the form of their wings, than they do their own congeners. This is the case with Acræa Thalia and Eueides Pavana, with Heliconius Eucrate and Eueides Isabella, and with Eueides Aliphera and Colænis Julia, which are deceptively alike, and the last two are connected with Dione Juno, at least by the upper side of the wings. The difficulty of judging of the relationships of the single species is thus much aggravated; it cannot be said how much of this resemblance is to be attributed to blood-relationship, and how much to deceptive imitation.
“As larvæ all the Brazilian species must be placed in one genus, as they agree exactly in the number and arrangement of their spines (4 spines, not in a transverse row, on segments 2 and 3; 6 spines, in a transverse row, on segments 4–11; 4 spines, not in a transverse row, on the last (12th) segment). They differ from one another much less in this respect than do the German species of Vanessa, such, for instance, as V. Io or Antiopa from V. Polychloros, Urticæ, and Atalanta.[224] The larvæ of Acræa Thalia are certainly without the two spines on the head which the others possess, and, on the other hand, they have a well-developed pair of spines on the first segment, which, in most of the other species, are completely absent; but this does not justify their separation, since the head spines of Heliconius, Eueides, and Colænis Dido, which are of a considerable length, are shorter than those of the next segment in Colænis Julia, and Dione Vanillæ, and in Dione Juno they dwindle down to two minute points, this last species also bearing a short pair on the first segment. The larva of Dione Juno is thus as closely related to that of Acræa Thalia as it is to that of its congener Dione Vanillæ.
“If it were desired to form two distinct larval groups this could not be effected on the basis of their differences in form, but could only be based on their food-plants. The larvæ of Heliconius, Eueides, Colænis, and Dione live on species of Maracujá (Passiflora); those of Acræa Thalia and Alalia on Compositæ (Mikania and Veronia). These larval groups would agree with those founded on the form-relationships of the imagines, but unlike the imaginal groups, which can be formed into families, they would scarcely possess a generic value.
“If we arrange the single species of caterpillars according to their resemblances, this arrangement does not agree with that based on the resemblances of the imagines, even if we disregard the different values of the groups. The result is somewhat as follows:—
IMAGINES.
(Nymphalideous butterflies with tufts on wing-veins.)
/---------------------------------------------------\
(Families.) MARACUJÁ-GROUP. ACRÆIDÆ.
/---------------------------\ |
/-------------------\ /-------------------\ |
(Genera.) Heliconius. Eueides. Colænis. Dione. Acræa.
| /-------\ /-------\ |
(Species.) Eucrate. Isabella. Dido. Julia. Vanillæ. Juno. Thalia. | | | | | | |
\----------+---------/ \--------/ \------/
\--------------------------------------/
LARVÆ.”