Зображення сторінки
PDF
ePub

footed butterflies. But, commonly, we can tell a Nymphalid from a Satyrid by this character. Again, on the hind wings, the Nymphalidæ proper show vein iv, entirely joined to the cubitus, and not issued from the cross-vein. In the Limnadidæ, Heliconidæ and Agapetidæ, which appear to form another branch of the “brush-footed” group of butterflies, this latter condition of vein iv, is only reached in a small group of specialized Satyrids, the Pararginæ. This character is plainly secondary, one which might occur independently in different groups not immediately phylogenetically connected.

The specializations of the lepidopterous wing, here chiefly considered, are visible among what I have called the “movable veins" and cannot be relied upon as decisive in general phylogeny. Their study leads to an arrangement of genera and species, in most cases upon a more positive basis, by supplying us with a gauge by which we may distinguish the younger from the older form. The norm by which these specializations are apprehended lies in the principle we have already set forth: the amount of the absorption is the measure of the specialization.

The two principal directions in which the specialization is manifested are: 1. the suppression of the media, common to both wings, and 2. the suppression of the branches of the radius, confined to the fore wings in most Lepidoptera and occurring sporadically. The latter is probably reminiscent of that action which has completed its task upon the hind wings of such Lepidoptera which have the radius already reduced to a single unbranched vein.

NOMENCLATURE. The application of literary terms to structural groups, wider in extent than specific, has become uncertain through the publication of varying and subjective opinion. It has, therefore, become necessary to associate the generic title with a single specific type, ascertained by historical methods, in order to go safely. The failure to employ the name of the genus in this manner renders Mr. Reuter's recently published volume at times unintelligible.

The same remark applies to Dr. Chapman's admirable paper on butterfly

1 Consult, “ Mittheilungen a. d. Roemer Museum,” 8, February, 1897; “ The Hind Wings of the Day Butterflies," Can. Ent., 29, 174; also several other papers more recently issued,

pupe, where exactly what is meant by the terms “Satyrus, Epinephele, Hipparchia," does not appear (Entom. Record, vi, 152). So far as the diurnals are concerned the authority I recognize is Mr. Scudder's Historical Sketch, Salem, 1875. Since, in exceptional cases, this work has been seemingly properly corrected and even in one case by the author himself, a republication up to date would be one of the most grateful of literary helps to the systematist, to whom it is a matter of comparative indifference what term he uses so that it is correct and exactly conveys his meaning, while it should be one necessarily understood. Since the difference between genera and species is quantitative, the limitations of the former will be always more or less a matter of opinion. As matters are now and unless a standard is recognized, the object of nomenclature will be defeated so far as generic titles used by themselves are concerned. Both to give greater endurance to his work and to make it a useful addition to generic definitions extant in literature, the systematist might confine his studies to species used for generic types as far as possible and neglect those not yet so favored. To locate and compare genera their types need alone be considered; by clearly explaining the structure of these incidental help will be afforded to reach an approxiinative agreement as to the limitation of generic groups. Generic terms should always have the same meaning attached to them, and this meaning can only be derived from the structure of their types. I remember that Moeschler, disputing the validity of the genera allied to Smerinthus and wishing to discredit minute generic differentiation, asked triumphantly, To what genus, then, do the hybrids between species belonging to these different allied genera belong? A little reflection might have led him to ask the question also, And to what species ? For although, to Moeschler, a genus would seem to have constituted a fixed quality, yet it is seen not to be so and that the genus idea is an extension of the species idea, and both ideal categories having a relative being without sharp outlines. In the formation of generic categories the idiosyncrasy of the describer comes easier to the surface, as in Mr. Scudder's genera; but for the purposes of the systematist these are as good as any, and better than most; all that is wanted being a certain name attached to a certain thing. The describers of species are the avant couriers of the systematists, one no more useful than the other, and any adverse criticism of the former class, who throw the first light upon our darkness, must be due to a lack of thought and considera

tion. Nomenclature itself belongs to letters and is part of the machinery which biologists must use to work with. And we may remember here the fact that we possess no entire and satisfactory definition for the term individual as used in biology. So that it perhaps naturally follows that we are at a loss to define adequately groups or associations of which the individual forms the unit. The following notes explain the changes made by me in

THE NOMENCLATURE OF THE PIERI-NYMPHALIDÆ. Agapetida.- I use this term instead of Satyridæ because the generic title Satyrus Latreille is preoccupied (Scudder, l. C., 265), and is properly replaced by the title Agapetes Bilberg, 1820 (l. C., 104), with the same type, A. galathea. It is impossible to separate the name of a higher group from that of the genus upon which it is based. If Satyrus properly falls then Satyridæ must also go. But the type of Satyrus remains and the new generic title of this type by natural right replaces the old title in all its various modifications. It appears that the more modern title Satyridæ replaces the Satyri of older authors who antedate the Tentamen in the use of a plural form, thus in recognizing a group or family in our sense. In addi. tion the term Oreas (Oreades) used by Hübner in 1806 is itself preoccupied. So that the claim of Agapetidæ to designate the family, with Agapetes galathea as its type, seems indisputable. Arge of Esper and also of Hübner would be preoccupied by Schrank (1. c., 117).

Limnadide. The earliest plural form applied particularly to a member of this group is Limnades of Hübner, 1806, based upon Limnas chrysippus as type. This must, therefore, replace the term Danaidæ of modern writers, a term based upon the later Danaus (plexippus) of Latreille, 1809, for which Scudder proposes to retain Danaida of the same author of 1805 (I. c., 153), perhaps disputably, since Latreille's change seemed warranted at that time. Once a synonym always a synonym.

in

any case the modern Danaidæ cannot claim any connection directly with the Danai festivi, etc., of Linné, since that group had no legal standing; no genus of that name upon which it could be based having been published. Cuvier's similar use of “Danai” included also the Pierida (1. C., 154), and, there. fore, Limnadidæ has a clear right to recognition.

N. B.-I take the opportunity here to change my term Capis to Capisella since there is an earlier genus, Capys of Hewitson, which

interferes (Proc. AMER. Philos. Soc., xxxiv, 434). I also resume my name for Lomanaltes lætulus, since from the description it must be that Mr. Walker's species differs.

GENERAL DESCRIPTIONS.

These are limited to the holarctic fauna, of which the principal genera appear to have been examined. There remain, however, several types I have been unable to obtain.

Pierida. Pierina.-Primary wings, specialization by suppression of the media : Traces of the base of the media in the shape of scars I have found in Eurymus and Callidryas. In Colias rhamni, a mimetic form springing evidently from the same line, I fail to find the least impression. Backward spurs occur in Aporia and faint traces in Callidryas. The cell nowhere completely opens. The cross-vein becomės partially degenerate in a number of instances. In all the genera yet examined, vein iv,, the upper branch of the media, leaves the cross-vein and is given off, outside of median cell, from the lower branch of radius. This character I only find again on the hind wings of Nemeobius. The middle branch of media leaves cross-vein above the middle and is radially inclined.

Primary wings, suppression of radial branches : End forms of specialization in this direction are offered by Mancipium, Pontia and Nathalis, where the five branches are reduced to three. The bulk of the forms: Pieris, Eurymus, Colias, Callidryas, Eurema, etc., are four-branched. As yet I find only certain of the Anthocharini, therefore the more generalized group, five-branched.

Secondary wings, suppression of media : Taking the homologies as given, the vein iv, assumes function and position of iii, on primaries; usually the piece between its base and the issuance of iii, from radius must be reckoned to cross-vein. The inauguration of the movement of the movable veins appears to take place on secondaries generally, since in a number of Lepidoptera vein iv, remains central on primaries, while on secondaries of same wings it inclines radially or cubitally. As on primaries, the cross-vein nowhere disappears in the Pierina and the cell remains closed.

Other features of specialization by absorption of veins : On primaries, vein viii is present, either as a scar or, in some instances, as an apparently functional, “tubular" vein. It takes the aspect of a short, oblique, more or less rigid piece, running from vein vii to internal angle. It has usually lost here the appearance of being

originally a longitudinal vein rooting in base of wing and, as in the Limnadidæ, appears more as a supporting strap. However, in Terias, where it is reduced, it assumes nearly the loop-like shape. The minute study of this vein is a matter of some difficulty. The appearance of vein viii in the Hesperiadæ corresponds essentially with that in the Sphingidæ and Saturniades, where it has the looplike shape. These quantitative changes are probably correlated with mechanical function. On the secondaries of the Pieridæ, there are but slight differences in the amount of absorption of veins ii and iii at base; on the whole, the absorption is small and herein is the wing generalized. Vein i, the so-called “præcostal spur," is usually present; it vanishes in the Eurymini and in Colias (Gonepteryx); it may be seen in Callidryas. There is no equality of specialization, no exact and equal step in all these instances and the position of a genus or group can here not be assigned with certainty from any one character. Better, as a guide, is the radial specialization on primaries, where it may be laid down as an axiom that the five-branched forms cannot possibly have been derived from the three or four-branched, and that they are consequently descendants of older types and clearly more generalized insects. But neither may we group all the three or four-branched species together, since these specializations are reached upon what are otherwise evidently independent phylogenetic lines, in all cases necessarily succeeding a five-branched ancestor. Thus the three-branched Pontia is clearly an offspring from the five-branched Anthocharini; the three-branched Nathalis is more immediately connected with the four-branched Terias and Eurema.

Leptidianæ.-So different is this butterfly and so isolated its present position, that we must almost leave it out of sight in discussing the specialization of the Whites. The suppression of the media is nearly limited to the extinction of the basal portion. The position of vein iv, is central, or very nearly so, on fore wings, cubital on hind wings; we have here an exceptional parallelism with Papilio. The radius is generalized, five-branched. No trace of vein viii appears on fore wings.

The median cells are small, retreating; the veins long. In comparison with the other whites, the wings are in a generalized state, but the chances are that in Leptidia (Leucophasia) we have a survival of what was a more extended group at one period and that the generalization is strictly relative. The disappearance of vein viii points in this direction.

« НазадПродовжити »