Samuel Hubbard Scudder

NOTICE OF INSECTS WHICH HAVE BEEN ERRONEOUSLY REFERRED IN RECENT TIMES TO BUTTERFLIES. 1 Cyllonium Boisduvalianum Westw. , and C. Hewitsonianum Westw.

Fig. 2.

Cyllonium Boisduvalianum Westw.

These two insects were figured by Westwood in the Quarterly Journal of the Geological Society of London for November, 1854, the former (reproduced in our fig. 2) on Pl. XVII, fig. 17; the latter (reproduced in our fig. 3) on Pl. XVIII, fig. 27. Of the former he makes the following remarks:[AX] “Pl. XVII, fig. 17 represents a number of fragments of delicate tegument, covered with minute punctures and traversed by straight and somewhat radiating veins, which appear like portions of the hind wing of some species of Butterfly, entirely denuded of scales.” The name is given to it in a note to the explanation of the plates, p. 395. Concerning the second he says:[AY] “Pl. XVIII, figs. 27 and 30, appear to be portions of the hind wings of some species of Butterfly; still they have very much of a vegetable aspect. The surface is covered with minute punctures, which may be the cells for the insertion of the quills of the coloured scales, which are all removed, supposing the specimens to be Lepidopterous.” The name we have quoted is given only to fig. 27, in a foot note on p. 396.

I have not been able to find, even with Mr. Brodie’s help, the first specimen referred to; but an examination of the original of the latter (see fig. 3) proved that, while it is unquestionably an insect, it cannot be referred to the Lepidoptera; the punctures referred to are both too large and much too irregularly disposed to have been the points of insertion of the scales; they are probably the marks of the insertion of hairs, such as are not uncommonly seen irregularly scattered over the wings of insects belonging to the other suborders. As the figure of the first species closely resembles in this particular the one I have seen, I am forced to the conclusion that neither of these wings are lepidopterous. Plainly, the only reason why a new generic name was appended to these forms was that their remains were too fragmentary to afford the slightest guess as to what modern genus they might be referred. The fossils came from the English Purbecks.

2. PalÆontina oolitica Butl.

The first notice I find of this remarkable and very interesting fossil is that published in various literary and scientific London journals reporting remarks given at a meeting of the Entomological Society of London, and which afterward appeared as follows in their Proceedings:[AZ]

“Mr. Butler exhibited a remarkably perfect impression of the wing of a fossil butterfly in the Stonesfield slate. It appeared to be most nearly allied to the now existing South American genus Caligo.”

A full description of this insect soon appeared in the author’s “Lepidoptera Exotica,” accompanied by a plate; both were afterward republished in the “Geological Magazine.” In fig. 4 we reproduce fig. 1 of his plates, representing the neuration of PalÆontina; and in fig. 5, fig. 2 of his plates, subsequently copied by “The Graphic.” A description of the genus and species is first given, which it is unnecessary to reproduce here; afterward, the following remarks:

“[126] Though a British insect, this species belongs to a group so completely tropical that I do not hesitate to describe and figure it in the present work; its nearest allies are the genera Caligo, Dasyophthalma and Brassolis, all three essentially tropical American genera.

“P. oolitica is especially interesting, as being the oldest fossil butterfly yet discovered; the most ancient previously known to science having been found in the Cretaceous series (white sandstone of Aix-la-Chapelle[BA]), whilst the bulk of the known species are from the Lower Miocene beds of Croatia; it is also interesting as belonging to the highest family of butterflies, and to a subfamily intermediate in [127] character between two others, namely, the SatyrinÆ and NymphalinÆ, whilst the more recently discovered fossils are referable, with one exception, to the two latter groups. The nervures appear to have been impregnated with iron, which will partly account for their well-defined condition.”

Happening to be in London not long after the publication of the description and illustration of this insect, I took pains to make a very careful examination both of the original specimen, which Mr. Charlesworth kindly allowed me to study at my leisure, and of its reverse, which is preserved in the School of Mines, Jermyn street. I mentioned to Mr. Butler and to others, my conviction that the insect was to be considered homopterous rather than lepidopterous, and on my return to America, exhibited before the Natural History Society of Boston, drawings which I had made from the originals; my comments at that time were published very briefly, as I was reserving the proof of my statements for the present paper. Mr. Butler, however, was induced by this publication[BB] to examine the reverse at the Jermyn street Museum, and although he had been supplied by me with a rough tracing of the drawing I had taken of it, he failed to be convinced of any mistake, and published a paper in defence of his own view in the Geological Magazine for October, 1874. In this paper he gives new drawings of the insect, quotes portions of letters in which I had expressed my opinions upon the nature of the fossil, gives the remarks referred to from the “Proceedings of the Boston Society of Natural History,” and makes, among others, the following comments.

“Seeing that Mr. Scudder had made his views public, I felt that it was time for me to take similar steps on my side. I therefore availed myself of an early opportunity of again visiting Jermyn street, where, through the courtesy of the officers, I was enabled to make a sketch of the impression in the Museum. I found it impossible to make a tracing of it, and therefore drew the whole by measurement. This sketch is now produced on Pl. XIX, fig. 4 [see fig. 6]; and any body can judge for himself whether or not it is more perfect than that which I previously figured (see Geol. Mag., 1873, Vol. X, p. 2, Pl. I, fig. 2 [see fig. 5]).”

“In order to show the extent to which the Jermyn street example is deficient, I have restored it (fig. 5 [our fig. 7]), filling in the blanks from Mr. Charlesworth’s specimens. By comparing the latter with the wing of Dasyophthalma (fig. 1), and Cicada (fig. 2), one may come to a pretty accurate conclusion as to the group of insects to which it ought to be referred.”[BC]

The neuration of Lepidoptera as a group is the simplest in the whole order of insects, if we except that of the elytra of Coleoptera; this is due, doubtless, to the fact that their wings are heavily scaled, concealing the nervures; just as in Coleoptera, the thickness and opacity of the fore wings often completely masks the neuration.

The normal number of veins in the wings of insects is six, disposed to a certain extent in pairs; the middle pair usually ramify to a greater extent than the others, and support most of the membrane of the wing. In butterflies the foremost vein is always absent and very commonly the hindmost, so that there are but five (often but four) principal veins, usually designated, though not very appropriately: costal, subcostal, median, submedian and (when present) internal, reciting them in their order from in front backward. The costal, submedian and internal nervures are invariably simple and terminate at the margin, or are occasionally lost in the membrane of the wing. The subcostal and median nervures, on the other hand, are as invariably forked, and with their branches support nearly the entire wing; the subcostal nervure curves downward and the median upward so as to meet, or nearly to meet, not far from the middle of the wing, and to enclose between them a large space called the discoidal cell; the branches of the median nervure are all thrown off from its lower edge before union with the subcostal; the principal branches of the subcostal nervure are, on their side, thrown off from its upper edge; but, as the nervure curves downward at the extremity of the cell, another set is thrown off (at least in the fore wings) from the lower edge; and it is these veins, rather than the subcostal nervure proper, which unite with the median to close the cell.[BD] None of the median, nor any of the inferior subcostal nervules are ever branched; but at the apex of the wing, where the play of neuration is usually the greatest, the last superior subcostal nervule is occasionally forked in the front wing. This is the only forked branchlet in either of the wings.

The last figure of P. oolitica given by Mr. Butler agrees in all its essential features with his first illustration. They both represent a front wing with four principal nervures,—costal, subcostal, median and submedian; the costal nervure is swollen at the base and extends, unbranched, to the tip of the wing; the median nervure is three-branched, the three forks simple, equidistant, emitted from the apical half of the vein, which at its extremity is united by a cross vein to a branch of the subcostal, closing the cell; the submedian nervure is simple and divides the space between the median vein and the margin of the wing. So far all is in accordance with the lepidopterous type; but when we examine the subcostal vein, which occupies nearly half the wing, the resemblance ceases altogether. This vein is represented as bearing no superior branches, but as sending out from its inferior surface three distinct veinlets, the first and second of which again emit a tributary from their inferior surfaces. This is a structural anomaly which finds no counterpart whatsoever in any family of butterflies. So that should we accept Mr. Butler’s own sketch of the fossil as correct, it would be impossible to consider the wing that of a butterfly.

In his description of the insect Mr. Butler compares the neuration to that of Caligo, and says its nearest allies are Caligo, Dasyophthalma and Brassolis. In his latter paper he figures the wing of a Dasyophthalma by way of comparison. In the genera named all the branches of the subcostal nervure are simple, and are thrown off from the superior surface, excepting the single set which is emitted from beneath, and which marks (as in all butterflies) the limit of the discoidal cell; this corresponds fairly with the first set of inferior veins emitted by the subcostal vein in the fossil; for the other sets, however, no counterpart will be found in the living types.

It was probably Mr. Butler’s want of familiarity with fossils that led him to overlook several features which can be seen in these originals. Having first traced the outline of the wing and the general course of the veins directly from the specimens, I subsequently filled in by measurement all the other parts which I could follow, studying each vein, or supposed vein, with the utmost care, from one end to the other of its course. The result of that study is presented in fig. 8, which differs essentially in its details from the illustrations given by Butler, and looks, as he himself confesses, “exceedingly anti-lepidopterous.” In the first place, the wing is much narrower than depicted by him; and at the extremity of a vein (the submedian vein of Butler’s sketch) there is a slight but decided bending inward of the membrane, as very frequently occurs at the line of demarcation between the middle and inner area of the wing in all or nearly all the lower suborders of insects, but never, so far as I am aware, in Lepidoptera. What he has given as a simple costal vein is neither swollen at the base nor simple, but has two inferior branches near the middle of the wing, united near their origin by an oblique cross vein. Branching of the costal vein is unknown in Lepidoptera; but if it should be claimed that this might be the subcostal, just as much difficulty will be encountered with the structure and relationship of the veinlets below, which must then be considered as belonging to the median vein; in no Lepidoptera can any such irregularity be shown, nor so disproportionate a magnitude of the area covered by the median nervure and its branches; a branched internal vein and cross-veins, which probably united all the longitudinal nervures at no great distance from the outer border (but which can only be certainly predicated for the lower three median interspaces), place this insect wholly beyond the pale of the Lepidoptera. It is but fair to say that Mr. Butler, having examined the original after he had in his possession a tracing of fig. 8, denies the existence of the cross-veins; there is one point, however, which an unprejudiced examination of the fossil cannot fail to show; that Butler’s “fourth branch” of the subcostal[BE] arises not from his third branch, but from his upper discoidal vein; if he can reconcile either this or the points already referred to (on the supposition that his sketch is otherwise an accurate one) with the neuration of any group of butterflies, the writer will be the first to acknowledge it.

As our only purpose in this place is to deny the lepidopterous character of PalÆontina, it is unnecessary to say anything in defence of the view we have expressed of its homopterous affinities; the superior position of the cell, the position and character of the lower cross veins (which we believe really traversed the entire wing), with their origin at the indentation of the lower border, suggest such a relationship, although there are not a few points in which it differs somewhat strikingly from living types.

The discovery of a fossil in the cabinet of the Rev. Mr. Brodie, which was found in England at the same or nearly the same horizon, as P. oolitica, and which seems to be a pupa case of one of the Cicadida of rather unusual size, renders my suggestion more worthy of credence.

At the conclusion of his latter paper Mr. Butler draws attention to the fact that Messrs. Westwood and Bates had expressed their agreement with his views. It should, however, be borne in mind, that, so far as appears from any facts which have been published, these gentlemen, whose well considered views upon the subject would unquestionably be of great weight, expressed this assent only upon a brief evening examination of a very obscure fossil in a poorly lighted hall, and before any one had questioned its lepidopterous character.