Fossil Butterflies / Memoirs of the American Association for the Advancement of Science, I.

by Samuel Hubbard Scudder

In this paper he quotes Boisduval’s locality “Aix en Provence,” but when he next refers to this insect[P] he gives it as from “Aix-la-Chapelle, White sandstone,” a mistake, however, corrected subsequently. In this latter paper he remarks:

I have discussed the position of this species in my catalogue of Satyridæ, pp. 189, 190; showing that its nearest ally is Neorina Lowii, a common Bornean species, but that it also has a slightly more distant relationship to Antirrhæa Philoctetes and Anchiphlebia Archæa, two common tropical American forms; the amount of affinity, as regards the first two of these species, may be seen on my plate, figs. 4 and 5; the resemblance to Anchiphlebia is less striking, and the affinity more doubtful; it has nothing to do with Cyllo.

That Butler should have so nearly pointed out the exact affinities of this insect from the simple study of Boisduval’s plate, is unquestionably due to his extended familiarity with butterflies, and especially with the forms of this subfamily; but it also shows the essential harmony between the markings of the under and upper surface of the wings of butterflies, notwithstanding their frequent great dissimilarity; for Butler compares this fossil with the recent forms on the assumption that the under surface of the wings is seen in Boisduval’s plate.

The actual condition of the fossil, for an opportunity of examining which I am indebted to the courtesy of Count Saporta, is this (see [Pl. I], fig. 13): The thorax, hind legs and both pair of wings of the left side are preserved, almost completely; all the rest is lost. The thorax is viewed from above and somewhat on the left side; the hind coxæ seem to be almost torn away from their immediate connection with the trunk. The two hind legs are stretched out bent at the femoro-tibial articulation; the left leg lies above both the wings and is apparently attached throughout, although its base is covered a little by the crushed body; the right leg lies below both the wings and is apparently partially detached, though but slightly, from the coxæ; the tibio-tarsal articulation can be distinguished ([Pl. I], fig. 11) but not the tarsal joints. The wings are bent over downward in a position the reverse of that of repose. The fore wing covers the hind wing as in nature, but to such an extent as to conceal the greater part of it; the guttered portion of the inner margin of the hind wings is almost fully expanded, but apparently has a fold next the submedian nervure. The fringe of the fore wing seems to be gone, but that of the hind wing is preserved nearly throughout. Head, fore and middle legs, wings of the right side and abdomen are wholly wanting.

The upper surface of the wings is, therefore, the part which attracts most attention. That it is the upper and not the under surface which is exposed to view is shown by the relation of the wings to each other ([Pl. I], fig. 10), by their unquestionable attachment to the thorax, of which we certainly see only the upper portion with its smooth arched dome marked by the sutures which separate the portions which compose it; and by the design itself of the wings, which is such as pertains to the upper rather than to the under surface of butterflies of this group. These markings are most wonderfully preserved; and the careful and prolonged study I have given every part of the fossil has enabled me to separate, with a considerable degree of certitude, the markings which appertain to the fore wing and those which belong to the hind wing. Those of the latter are generally to be traced through the semi-diaphanous fore wing and are given in [Pl. I], fig. 8. One is aided greatly in this investigation by following the lines and series of markings which extend over both the exposed and covered portions of the hind wing; and then by comparing the fainter and obscurer tints of the covered portion with equivalent marks on other parts of the stone covered by both the wings; in this way the markings of the hind wing may be separated from those of the front wing, but subject, certainly, to some degree of doubt. In the figure upon the plate ([Pl. I], fig. 8) the portions to which the least degree of doubt attaches are the outer halves of the two wings. I am inclined to consider these as almost absolutely accurate. The parts on the other hand which are more likely to be inaccurate are the basal halves of the median interspaces of the fore wing and the contiguous portion of the medio-submedian interspace. Assuming, however, that the drawing faithfully represents the real markings of this extraordinarily preserved fossil, a detailed description of its features follows.

The basal portion of the fore wing ([Pl. I], fig. 8) is very dark, and increases in intensity toward the border of the innermost light patch; the latter is bounded by a line running in a nearly straight course from the costal nervure, opposite the middle of the upper border of the cell, toward the middle of the apical half of the submedian nervure; but it extends slightly outward on reaching the lowest median nervule and just below this turns baseward and makes a large ovoid curve of an interspace’s diameter, returning to its course when it has nearly completed the circuit and reached the middle of the medio-submedian interspace; the outer limit of this large pale patch, which crosses the cell and extends nearly to the middle of the lower median interspace, nearly follows a line running from the upper extremity of the inner border to and along the middle median nervule. Beyond this the upper half of the wing, half-way to the apex, is nearly as dark as the basal part, excepting in a large light patch which crosses the lowest two subcostal and the subcosto-median interspaces, is broadest in the middle, but twice as broad at the upper as at the lower extremity, and rounded throughout excepting at the angular upper basal corner; its interior margin is sharply defined, and is nearly parallel to the interior border of the inner light patch, extending in a straight line from the subcostal nervure midway between the origin of the first and second superior nervules to the upper median nervule, about as far from its origin as it is from the base of the first median nervule; the exterior border is powdery, strongly convex and, starting from the subcostal nervure midway between the bases of the second and third superior nervules, joins the other border on the last median nervule; this patch is twice as long as broad. Extending from the next to the lowest subcostal nervule to the internal nervure, parallel to the outer border, is a broad indistinct pale band, broadening below, and on either side merging indefinitely into the darker parts of the wing, separated from the light patches by only a narrow belt of dark scales, which becomes narrower and fainter in the lower half of the wing; at its broadest the pale band is a little broader than an interspace, and it contains in its middle and at the middle of each interspace, as well as in the next to the lowest subcostal interspace, a series of large circular dark spots, of nearly or quite half the width of the interspaces in which they fall, often, and especially in the upper interspaces, enclosing a small black pupil; these spots are almost exactly parallel to the outer border, that in the lowest median interspace with its outer border at an interspace distance from it; with the exception of that in the lowest subcostal interspace, they are each surmounted interiorly by a much smaller circular light spot, the centre of which is near the circumference of the larger spot, so as to infringe upon it; with the exception of the uppermost, which is nearly as large as the spot on whose summit it is placed, the light spots are of nearly equal size and about one-third of an interspace in diameter; or if anything the two lower, seated on the largest spots, are smaller than the others; the wing must have been wrinkled between the nervules next the outer border, as shown by the dark lines running from the border to the centre of the dark spots. The outer edge and the apex of the inner are uniformly dusky and rather lighter than the other dark parts of the wing; the fringe is evidently lost.

The hind wing is very dark at the base, like the fore wing, nearly as far as the extreme tip of the cell; this dark area merges gradually into a lighter portion, which crosses the wing as a very broad equal band having its outer limit at a narrow, dark, regular belt, with ill defined outline, which crosses the wing subparallel to the general course of the outer border a little within the middle of the outer half of the wing; within this broad light band are two narrow transverse powdery streaks of dark scales, one extending from the extreme tip of the cell, and broadening a little in its course, running in a curve opening inward to the inner border; the other starting from the same point in an opposite direction, and passing in a sinuous course, with varying width, toward the middle of the basal two-thirds of the upper subcostal nervule, hardly separate from the outer limits of the dark base of the wing. The darkest part of the narrow band in the middle of the outer half of the wing has a regular curve and strikes the borders in the middle of their outer halves; there is a submarginal slender dark streak, separated by scarcely more than its own width from the outer border, becoming narrower toward the costal and inner borders, and especially towards the costal; it is broken at the upper median nervule, where the upper portion joins a second broader band, separated by a space nearly equal to itself from the submarginal band; this leaves a nearly equal light band in the outer part of the wing, broadest above and reaching from the costal border, almost to the inner; along the middle of this belt is a series of six round dark spots and ocelli, one in each of the interspaces excepting the costo-subcostal; the largest is in the lower median interspace, and is a spot nearly as broad as the interspace, deepening toward the centre to a black pupil; the next largest, in the upper median interspace, is an ocellus with a black pupil, immediately followed by a pale annulus, again surrounded by a dark ring of equal diameter, the whole a little more than half the width of the interspace; next larger are two spots of less intense depth of color, one in the upper subcostal, the other in the subcosto-median interspace, about one-third the width of the interspace, the upper deepening, the lower becoming paler at the centre; the spot in the lower subcostal and the medio-submedian interspace are equal and smallest, about one-fourth the width of the interspace, and consist only of rather faint, powdery marks, a little darker towards their centres. The fringe of this wing seems to be preserved and is short, nearly equal, dark, resembling a repetition of the submarginal streak.

Length of fore wing, 37mm.; breadth of fore wing, 20·5mm.; length of hind wing, 31·75mm.; length of tail, 4mm.; distance of the base of the second superior subcostal nervule of hind wing from the divarication of the costal and subcostal nervules, 5·55mm.; rows of scales in the subcostal region of the fore wings, ·075mm. apart; length of thorax, 5mm.; of hind femora, 4·6mm.; of hind tibiæ 4·8mm.; of hind tarsi, 4·9mm..

Tertiaries of Aix, Provence, France; collection of Count de Saporta.