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ART. XXIV. AN ACCOUNT OF SOME INSECTS OF UNUSUAL INTEREST FROM THE TERTIARY ROCKS OF COLORADO AND WYOMING.

BY SAMUEL H. SCUDDER.

An examination of an extensive series of fossil insects recently obtained in different parts of the Rocky Mountain region has brought to light a large number of remarkable forms. To illustrate this, and as an indication of what we may expect further researches will reveal, I have brought together in this paper a few examples from different orders. These, however, are some of the most striking. It will scarcely fail of remark that those which come from the Florissant beds indicate a tropical relationship to a conspicuous degree. Perhaps this selection may show it to a far greater extent than a more systematic one would do; but my studies are constantly revealing similar affinities, leaving no doubt in my mind that the faunal elements of Tropical America of to-day entered largely into the insect-life of the central United States in Tertiary times. Similar tropical characteristics have already appeared in other Tertiary insects I have examined, such as in the Orthoptera previously described from Florissant, the Entimus, the Aphana, and perhaps the Cyttaromyia from White River, and possibly also the Lithortalis from British Columbia.

The beetle described below (Parolamia rudis), however, is of an Old World rather than a New World type.

Perhaps the most generally interesting insect will be thought to be the fossil butterfly (Prodryas persephone), which is so perfect as to allow description of the scales, and, besides being the first found in America, is far finer than any of the nine specimens which have been discovered in Europe, and shows, moreover, some features betokening its antiquity. The fly (Palembolus florigerus) is interesting, not only as representing a highly specialized type hitherto unknown on this continent, but as showing how the semblance of an original vein may be formed in the wings out of mere fragments of distinct veins, affording, indeed, a better example of this feature than living members of the same group in other parts of the world.

The insects from other places than Florissant are described on account of their remarkable character. The eggs of the Corydalites are, so far as I know, the first insect-eggs that have been found in a fossil state; but aside from that, they have an intrinsic interest. The Dysagrion from Green River is of a marked tropical type; while the cases of the caddisfly enable me to draw the attention of collectors to the occurrence of such objects in a fossil condition.

LEPIDOPTERA: PRODRYAS (zpó, ôpúaz).

A stout-bodied, strong-winged genus of Præfecti. Eyes moderately large. Antennæ remarkably short, scarcely longer than the head and thorax together, the club moderately long, obovate or subfusiform, about` twice as stout as the stalk, about five times as long as broad, broadly and regularly rounded at the tip, and composed of eleven or twelve joints of nearly equal length. Palpi extending beyond the front of the head by a little more than the length of the apical joint; the latter about five times as long as broad, equal, cylindrical, broadly rounded at the tip, and uniformly clothed with slender scales; the middle joint appears to be moderately slender and compressed, twice as broad as the apical joint.

The thorax is stout, with the general form of the Præfecti, and particularly of the special group to which Vanessa and Hypanartia belong. The median ridge of the mesothorax has a minutely impressed line posteriorly; the scutellum is pretty large, lozenge-shaped, slightly broader than long; the metathoracic epimera are pretty large, and taper apically at the median line of the thorax to a blunt point. The legs are too im perfectly seen through the wings to give even the length of any part or of the whole of any one with probability. Posterior lobe of patagia about twice as long as its mean breadth, curving outward and tapering regularly and rapidly to a somewhat produced outer apical angle.

Fore wings nearly twice as long as broad, unusually triangular, the costal margin almost exactly straight, but bent with a posterior curve at the extremity, and slightly convex at the extreme base; the outer margin is also nearly straight on either of its two halves, separated by a slight bend at the extremity of the upper median nervule, the lower half faintly convex; the inner margin is straight, the outer angle only a little rounded. The costal nervule terminates at the middle of the wing. The first superior subcostal nervule originates shortly before the origin of the first inferior subcostal nervule, and terminates scarcely beyond the middle of the third quarter of the wing; the second superior and second inferior subcostal nervules originate in the middle of the wing, the latter from the first inferior branch, as far beyond its base as the first superior nervule before it; the former terminates at the middle of the outer half of the costal border; the latter diverges from the first inferior branch so slightly as to be nearly continuous with its basal portion; the third superior branch originates as far beyond the second as the second beyond the first, and the fourth midway between the third and the outer margin; the latter is widely parted from the main vein, and strikes the costal margin as far beyond the obtuse but distinctly angled apex of the wing as the main branch passes below it. The cell is open. The first median branch originates midway between the base and the final forks, and the latter diverge very slightly at base, leaving a very open and broad subcosto-median interspace.

Hind wings shaped somewhat as in Hypanartia, the costal border beyond the great rounded prominence of the extreme base being very gently convex, the outer margin full on the upper half, the upper outer angle broadly rounded; the upper median nervule is developed in the middle of the wing into a long, slender, tapering tail, and the lower half of the wing is strongly crenulate, and especially roundly excised in the lower median interspace and lobed on the lowest median nervule; the lower outer angle is well rounded; the inner margin plainly forms a gutter for the reception of the abdomen. The costal and precostal veins are very doubtful, being exceedingly obscure on the specimen; but the former apparently arises from the common stem of the costal and subcostal veins at right angles to it shortly beyond the base, and then curves strongly outward subparallel to the costal margin, striking the latter in the middle of its apical half; while the precostal is a simple recurved vein, directed inward and forward at the sharpest point of the costal curve. The subcostal vein is peculiar in that its first branch, originating only a little beyond the costal, approximates so closely to the costal margin as to strike scarcely outside of the upper outer angle of the wing, a place usually reserved for the apex of the costal vein; the subcostal forks again, scarcely more than one-quarter way from the base of its first branch to the margin, the middle branch continuing the curve of the main stem, and the lower branch diverging very gradually from it, and widely distant from the median vein. The main stem of the latter, with its upper branch, forms a gentle sinuous curve scarcely approaching the subcostal vein (the cell being open), and emits its first branch in the middle of the cell, or scarcely more than half-way from the base to its final divarication. This latter is unusually slight, the middle branch keeping throughout very close to the upper and distant from the lower branch. The submedian strikes the angle of the wing as far from the lower branch as it is from the middle branch of the median. The internal nervule cannot be determined.

The abdomen is full, with the third and fourth joints longest, the whole nearly twice as long, and in the middle fully as broad as the thorax.

This is the first butterfly that has been found fossil in America, and as only nine species are known from the well-worked Tertiary strata of Europe, it may properly be esteemed an especial rarity. Besides this it has a double value: first, in that it is far more perfect than any of the European specimens (nearly all of which I have seen); and, second, in presenting, as none of the others do to any conspicuous degree, a marked divergence from living types, combined with some characters of an inferior organization. When first received, the tails of the hind wings and the tips of the antennæ were hidden by flakes of stone, and it was taken, both by myself and by every entomologist to whom I showed it, to be a Hesperian, the lowest family of butterflies. The neuration, however, which, although mostly very obscure, can be deter Bull. iv. No. 2- -14

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mined with certainty, shows it to be a Nymphalid, the highest family, with which the structure of the antennæ and palpi and the outline of the hind wings, now entirely uncovered, perfectly agree.. The first inference was drawn principally from the robustness of the body and the form, proportions, and markings of the front wings. The latter are unusually long for a Nymphalid of this type, have a remarkably straight costa, an outer border bent at the middle instead of far above it, and are possessed of a nearly transverse, median, light-colored belt on a dark ground, a subapical row of small spots depending from the costa, a spot in continuity with them in the upper median interspace, and beyond them, parallel to the outer border, in the costo-subcostal interspace, a pair of minute spots,-all characters perfectly consonant with Hesperian affinities; never combined, and each very rare in the Nymphales. It is not a little strange, however, that while the form and markings of the fore wings are hesperidiform, those of the hind wings are decidedly nymphalidiform. That the exact opposite should be a far more probable occurrence, follows as an assumption from the fact that, as a general rule, the front wings only of the lower Lepidoptera are ornamented, and that therefore the ornamentation of the hind wings is a more recent development. The somewhat variegated markings of the hind wings are indeed similar to what we find in certain Urbicolæ, such as Pythonides, but they are far more common in Nymphales, while the wing-contour is of a high nymphalideous type, quite above anything we ever find in Urbicolæ.

I am at a loss to suggest any really plausible explanation of the mode of development through which the hind wing should have attained an ornamentation consistent with its organization, while the ornamentation of the fore wings, whose structural framework has kept pace with that of the hind wings, has not advanced a single step beyond a type common to the lowest family of butterflies. It may, however, be suggested as a mere speculation that the position in which the wings of many Urbicola are held in repose (the front wings oblique or suberect, while the hind wings are horizontal, and therefore more fully exposed to view) might be productive of such a result. In this case, we should anticipate further indications of such a feature, at least in fossil forms. We are acquainted with the upper surface markings of both pairs of wings in extinct butterflies only in Neorinopis sepulta (Boisd.) Butl. and Thaites ruminiana Heer. It had escaped notice in my original study of these,* that when they are compared with living types, indications appear of precisely the same nature, although by no means so conspicuous. The rude patches of color that mark the discoidal area of the front wings of N. sepulta, and the repetition of almost similar, unbroken, transverse bars on the same portion of the front wings of T. ruminiana, when compared with these parts in their nearest living allies, are clearly

* Mem. Amer. Assoc. Adv. Sc. i, 1875.

indications of an inferior as well as an earlier type, while no such contrast is presented in the delicate shading and more complicated pattern of the hind wings. But, again, a partial comparison may be made with the markings of the front wing alone, and in the seven other species of described fossil butterflies there is not one, with the possible exception of Eugonia atava* (Heer) Scudd., in which the markings may be looked upon as less highly developed than in the living types.

Instances could, of course, be easily given from among living types in which the ornamentation of the upper surface is less variegated in the fore wings than in the hind pair, but it might readily be doubted whether this should be looked upon as having any direct bearing upon this subject; yet, even if none could be cited, it may fairly be urged that the lapse of time since the Florissant beds were deposited is amply sufficient for the loss of any such indication of hesperidiform affinities in a group of insects so pliable in ornamentation as butterflies are shown to be by the mere facts of mimicry.

Prodryas shows further peculiarities when compared with its nearest living allies. In the Tropical American genus Hypanartia, which seems to be its nearest neighbor, as in all those closely allied to it at the present day, the costal margin beyond the base is uniformly arched throughout; and the outer margin, angulated in the upper half of the wing, is roundly excised below it, giving these butterflies the common name of "angle wings". They are insects of strong and rapid flight, capable of the most abrupt and unanticipated movements, making them very difficult of capture on the wing. The straight, strong costa and more elongated wing of Prodryas, on the other hand, with its nearly uniform straight, outer border, combined with the robustness of the body, indicate great strength of wing and a rapid direct flight, as in the Hesperides, but not the power of sudden turning.

In Hypanartia and its immediate allies, the cell of the front wing is closed, although by a feeble vein, and the superior subcostal nervules take their rise at more or less irregular distances apart, and run long distances crowded side by side; while in Prodryas the cell is open, and the subcostal nervules are much shorter and very uniform in their distribution; the inferior subcostal nervules also originate in Prodryas in a much simpler fashion, indicating that its ancestors never had the cell closed, although a foreshadowing of the closure may be seen in a row of special scales (or a line of color) at the supposititious termination of the cell. That this can hardly indicate a true vein appears from the fact that there is not the slightest tendency of the opposing veins to approach each other at its extremities-a tendency which it would seem should naturally precede the formation of a vein; the second inferior subcostal nervule takes its rise from the first in just about the same manner as

* The remnant of this insect's front wing is certainly simpler in markings than the upper surface of allied living Eugonias, but it may represent an inferior surface, in which case there is no special difference.

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