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the Parnassiinæ, the Riodini-Lycænidæ, as well as the Saturniades among the moths, the “brush-footed" butterflies (Nymphalidæ of Scudder and Comstock) as well as the Nemeobiidæ have no share and are hors de concurs.
We now come to the direction of the suppression of the media. Herein the Pieridæ lag behind the Nymphalidæ (in sensu mihi) with one remarkable exception in the position of vein ivı, the upper branch of the media, which ascends the radius (iii) to a point beyond the cell, a character repeated only on the hind wings of Nemeobius. In all the “brush-footed” butterflies this vein never leaves the cross-vein at the extreme upper corner of the median cell. Though the latter open and the disappearance of the media by the distribution of its branches between radius and cubitus become complete, still vein iv, never fuses directly with the radius. Did it do so its passage to a point beyond the cell in the process of specialization might be logically expected to follow. What power is it which keeps this vein apart, even in Nymphalis and Potamis, where, in the latter especially, the approximation is carried out so completely? Undoubtedly all these retained and abandoned positions for the veins indicate the action of the dynamical force which fits the wing for variations in the mode of fight. The field observations which are compared with the structure of the wings are as yet scanty in the extreme. I have only brought the opening of the cell and the radial position of iv, into a probable relation with a lofty and sailing flight, a tree life like that led by Potamis iris or Philosamia cynthia. The passage of iv, along iiig does not seem to help the wing to extended fights. We find it again in the moths, in the Smerinthinæ and Citheroniadæ. The bunching of the two upper branches of the media near the radius at this point seems, on the other hand, to strengthen the primaries. As these veins are retired from the radius and retain their original generalized position on the cross-vein, closing the cell, so does a more modest terrestrial habit of flight seem to prevail ; so that it seems probable that the Lepidoptera were not originally high flyers, and that those which now disport among the tree tops are the latest arrivals on their respective and differing lines of phylogenetic descent.
To return to our immediate subject, the comparison of the specializations of the Pierida and Nymphalidæ proper. So far as the suppression of the media is concerned, the advantage of the Nymphalidæ is quite clear when the most specialized forms are compared, but
even when we descend to the “ Fritillaries,” where the cell of fore wings closes and vein iv, becomes quite central, the superiority is kept up. For everywhere on the hind wings of the Nymphalidæ does the lowest branch of the media, vein ivg, completely fuse with the cubitus. The cross-vein above it is always very weak, and even vanishes in Araschnia, Melitæa or Euptoieta.
Leaving the two principal directions in which the movable veins show the effects of specialization, we can compare the Pieridæ and Nymphalidæ upon other points. The most important of these is the fusion of ii and iii upon the hind wings at base. Here the Nymphalidæ continue their advantage. In the Nymphalinæ the absorption extends even to the point of issuance of i, and this measure is attained in the most specialized of the Agapetidæ or “Meadow Browns," the Pararginæ. In the mass of the Nymphalidæ this excess is not reached and the point of absorption falls varyingly short. But still it is always carried to a further point than in the Pieridæ, where the union is very brief and apparently quite wanting in Leptidia. This character is plainly secondary and cannot of itself determine the phylogeny. Again, the amount of absorption of i may be compared, a vein which is relatively constant in its position upon ii, from which it issues. It did not always probably do so, for I have observed in Papilio, Zerynthia (=Thais) and Parnassius, the process by which it has come to be fused with ii, and in the present group traces of its independence may be found in the Limnads or "Milk Weed ” butterflies. In the Pieridæ this yein i, the so-called “præcostal spur," tends to be absorbed and disappears in Eurymus (Colias) and Colias (Gonepteryx). Here the parallelism in specialization with the Blues" is continued. But in the Nymphalidæ it appears everywhere to be strong and well-developed; it is here more generalized. Evidently the strong flight continued to call for a strengthening of the shoulder of the secondary wings. In the flutterings of the “ Whites," the "Meadow Browns," the “Blues," this need was not so felt and the vein would tend to disappear.
So much we may say in comparing the Pieridæ with the Nymphalidæ proper, and we may pass more quickly over our comparisons of the “Whitęs” with the remaining families of “ brush-footed” butterflies, the “ Nymphalidæ" of Scudder and Comstock. After we leave the Pararginæ, the scale of specialization comes to a standstill or turns gradually against the latter. In the Agapetinæ, con
taining the mass of holarctic forms of the “Meadow Browns,” the lower branch of the media on the hind wings no longer fuses with the cubitus, but, as in the Pieridæ, springs from the cross-vein, the piece between this branch and the cubitus varying in length, and by so much marking here the grade of specialization. Except that vein viii of primaries seems to have been entirely absorbed in the Agapetidæ, it becomes difficult to distinguish their wings from the Whites. In both groups the position of the radial branches is similar. In the male sex the Agapetids show very frequently a bladder-like swelling at the base of ii, iii and vii of primaries, or the swelling may be confined more or less to the first-mentioned veins. In Agapetes it seems confined to ii; I do not find it in my preparations of Oeneis ællo, of which, however, I am uncertain as to the sex. It is a secondary sexual specialization, of which traces occur also in the Nymphalidæ. Like the Pierids, the Meadow Browns tend to lose vein i of secondaries by absorption; I believe, on the whole, that Pyronia represents the most specialized form. The amount of fusion of ii and iii at base still continues greater as against the Pieridæ, but hardly holds its own in comparison with the Argynninæ. In the Morphinæ, which appear to me to be specialized Agapetidæ, the cell opens on hind wings, but remains closed on primaries. They resemble thus the Pararginæ at present rather than the Agapetinæ, and have sprung apparently from the latter. Else, in our holarctic forms, the cell does not open on either wing, while it becomes, in the specialized forms, partially degenerate.
In the Heliconidæ and Limnadidæ the generalization makes itself more and more evident. The strong veining, closed cells, central position of iv, all tell against them. Heliconius still lacks vein viii of primaries, but in Limnas it is stronger than in any Pierid. At the close Libythea recovers somewhat of the lost territory, but this isolated butterfly, difficult to intercalate in a sequence, cannot probably alter the average result. Taking this all in all, we must find I believe that the excess of specialization in the direction of the suppression of the media, and in the subsequent points here explained, on the part of the brush-footed butterflies, as a whole, cannot outweigh the absence of specialization by reduction of the branches of the radius; seeing also that only in one family, the typical Nymphalids, is that specialization of the media carried to an excess. We have also the difficulty of estimating the morphological value of the shifting of vein iv, in the Pieridæ. While we cannot
thus assent to the conclusion expressed by Prof. Comstock in Evolution and Taxonomy, that we find in the Nymphalidæ an even greater specialization of the wings than exists in the Pieridæ, we admit that the point of view from which this is regarded may influence any conclusion, while the unequal presentation of the changes in the wings renders a just weighing of the differences a matter of some difficulty. It will be sufficient for my present purpose if the impression left on the mind of the reader is that rank is a relative conception and that it is owing to the constitution of our minds that we are impelled to string one natural object after another, while we are apt to fortify a classificatory preference for a special group out of several lying nearly abreast, by reasons which, sufficiently telling as far as they go, are apt to reflect only one side of a complex subject. I think, then, we may believe that the specialization of the “ brush-footed” butterflies is more apparent in the feet than in the wings, and that, if we are not inclined to give them preëminence on that account in our sequences, we shall not be induced to do it upon the statement of Prof. Comstock herein discussed and illustrated.
PHYLOGENETIC LINES AMONG PIERID GENERA. I have previously shown that coincidence in the number of the radial branches in reduction does not determine common descent, but that a three-branched condition of the originally five-branched radius has been reached independently, not only in different families, but on different generic lines within the same group. It may be assumed that three-branched species, differing otherwise unessentially, are correctly associated by this character; but to use this character anywhere alone for taxonomic purposes, or to assign it a commanding value, would be plainly to go wrong. It is probable, for instance, that the three-branched radius correctly indicates that the species of Thecla (in sensu mihi, with the type given by Scudder) are monophyletic and that the four-branched Zephyrini stand, at least constructively, as representing the original condition of their ancestors.
Under these views we may sort out several different lines of probable descent in the holarctic Pieridæ, in which the examples of extreme reduction have been independently developed. It is clear, since nature does not proceed by jumps, that the missing stages between the five-branched ancestors and the three-branched de
scendants have existed and that forms, which have retained the initermediate character and thus represent an earlier condition, may yet be found and correctly identified. So that we must seek out forms whose main disparity consists in their respective state of specialization of the wings.
Referring to the accompanying phylogenetic table, we may commence our brief study with the so-called “Yellows.” In Eurymus (Colias) the second branch of the radius has passed from its normal position before to one removed beyond the cross-vein. In Meganostoma this branch has only progressed to a point opposite the cross-vein. Clearly, Eurymus is the more specialized and younger form since this passage of iii, along the main branch of the radius is one indicated on different phylogenetic lines and is evidently a phase of general process by which the radial branches are reduced in number. The normal five-branched radius has this branch, following iiij, before the cross-vein. Under this view Meganostoma is the representative of the primitive form of Eury
The “ dog's head” pattern has probably yielded to the terminal band, straightly margined and the reappearance of the “dog's head” in species of Eurymus is due to "reversion." In other words, such species are the more generalized. But, while in the type, hyale, the distance which the vein iii, has traveled is a considerable one, it is much reduced in another species, edusa', which is more generalized in this way than E. hyale. From the multiplicity of species of Eurymus, especially in North America, it is not improbable that intermediate grades occur uniting the extremes E. hyale and M. cæsonia. I have not yet found them and Eurymus is yet separable from Meganostoma on this character. For purposes like the present study it is immaterial, so far as the use of the two generic names is concerned, whether such forms are found or not. The systematist needs both terms to designate different grades of specialization. The change in pattern involves a loss of black and not improbably does there exist a tendency, in the direction of specialization, to lose this and perhaps other darker colors upon
the same immediate lines. It is hardly probable that Callidryas is on the direct line of Eurymus, but it represents, in the holarctic fauna, an ancestral phase of development. It has the same four-branched radius, but vein
1 Mr. Meyrick's figure of edusa (Handbook, 350) is too inaccurately drawn to be of service.