But a single family of butterflies, then, is unknown in a fossil state,—that of Rurales; and since this comprises, in the main, insects of exceedingly delicate structure and of small size, their absence is by no means unaccountable. Yet, as we shall see further on, there are intimations of the presence of some of their caterpillars in amber, and an obscure and doubtful reference to a fossil Polyommatus from the beds of Aix.
If we enquire where the allies of these nine fossil butterflies are now living, we must seek for those of four of them in the East Indies; for those of three of them in America, and especially in that part lying on the confines of the tropical and north temperate zones; for those of one of them in the north temperate zone of both Europe-Asia and America; and for those of one in the Mediterranean district; for those of two only, therefore, out of the nine, or less than one-fourth, in the region where the fossils were discovered. Analyzing this point still further, we notice that three out of the four species whose living allies are to be sought in the East Indies come from the older deposits of Aix, and that only one of the two remaining Aix species shows special affinities to American types; we thus find here, as among other insects and among the plants, a growing likeness to American types as we pass upward through the European tertiaries.
The study of the floras of the European tertiaries has proceeded so far that in most cases we are able to find, in the very beds where the butterflies occur, plants which we may reasonably judge to have formed the food of these insects in their earlier stages. In but a single instance is the family of plants, upon which it was necessary, or almost necessary, to suppose the caterpillar fed, entirely absent from tertiary strata; and since this family is the Cruciferæ, which in its very nature could scarcely have left a recognizable trace of its presence, the exception has no force.
After presenting these facts, for convenience sake, in a tabular form, we will pass on to the enumeration of those fossils which have been referred to butterflies, but whose exact position is still unsettled.
TABULAR VIEW OF FOSSIL BUTTERFLIES.
| Names of Species (and families). | First referred to genus. | First described by | When described. | Found in | Geological Horizon. | Preserved in Museum of | Nearest living allies found in | Probable food of caterpillars. | Parts of wings preserved. |
| (Nymphales). Neorinopis sepulta Butl. | Cyllo. | Boisduval. | 1840 | Aix. | Ligurian, (upp. Eocene). | Count Saporta, Aix. | E. Indies. | Gramineæ. | Perfect wings of one side. |
| Lethites Reynesii Scudd. | Satyrites. | Scudder. | 1872 | Aix. | Ligurian,(upp. Eocene). | Marseilles. | E. Indies. | Gramineæ. | Both fore-wings nearly perfect, superimposed. |
| Eugonia atava Scudd. | Sphinx. | Charpentier. | 1843 | Radoboj. | Mayencian, (mid. Miocene). | ? | North temperate Zone. | Salix, Populus or Betula. | Upper half of one fore-wing. |
| (Papilionidæ). Mylothrites Pluto Scudd. | Vanessa. | Heer. | 1849 | Radoboj. | Mayencian, (mid. Miocene). | Hof mineralien-Kabinet, Vienna. | E. Indies. | Leguminosæ (Capparis?). | Both fore wings nearly perfect. |
| Coliates Proserpina Scudd. | —— | Scudder. | 1875 | Aix. | Ligurian, (upp. Eocene). | Count Saporta, Aix. | E. Indies. | Smilax. | Two fore-wings superimposed. |
| Pontia Freyeri Scudd. | Pierites. | Heer. | 1849 | Radoboj. | Mayencian, (mid. Miocene). | Hof mineralien-Kabinet, Vienna. | Temperate America. | Cruciferæ? Terminalia?? | One fore-wing nearly perfect, but neuration obscure. |
| Thaites Ruminiana Heer. | Thaites. | Scudder. | 1875 | Aix. | Ligurian, (upp. Eocene). | Professor Heer, Zurich. | Mediterranean district. | Aristolochia. | All the wings; those of one side nearly perfect. |
| (Urbicolæ). Thanatites vetula Scudd. | Vanessa. | Heyden. | 1859 | Rott. | Aquitanian, (low. Miocene). | British Museum. | Subtropical N. America. | Leguminosæ (Hæmatoxylon Gleditschia). | All the wings, but superimposed and very obscure. |
| Pamphilites abdita Scudd. | —— | Scudder. | 1875 | Aix. | Ligurian, (upp. Eocene). | Marseilles. | Tropical America. | Gramineæ. | One fore-wing perfect. |
In the earliest accounts that we have found, including all those in the last century, the generic term Papilio was used for all Lepidoptera, and therefore we cannot be certain whether butterflies or moths are meant. Hueber’s plates, even, are so inferior that they afford no additional aid; but those of Sendel possibly represent, as we have noticed in the Bibliography at the commencement of this memoir, the early stages of butterflies preserved in amber. The only other direct references to butterflies preserved in amber are the following: Gravenhorst,[AV] in his enumeration of amber insects, gives under the Lepidoptera forty specimens referable to Tineæ and Tortrices, and besides these “mehre Raupen, sämmtlich, wie es scheint, Schildraupen, denen des Papilio W. album ähnlich.” The probable nature of the ancient forest yielding amber renders it unlikely that any butterflies in their perfect state would be found in it. As a rule, butterflies are eminently fond of the light. This has already been remarked by Menge:[AW]—“Das fehlen gröszerer Schmetterlinge im bernstein deutet auf einen finstern undurchdringlichen urwald, den die kinder des lichts gemieden haben.” Yet as some Theclas do feed upon coniferous trees, it is not impossible that the onisciform larvæ, referred to by Gravenhorst, may belong to this group. As far as we can discover, no further reference is made to them, excepting by Giebel and Bronn in some of their lists and enumerations of fossil insects. The writings of Berendt, Menge and others, all bear testimony to the great rarity of Lepidoptera in amber, and most of those which have been discovered belong to the lowest two families, above referred to.
Dr. Hagen informs me that he has himself seen specimens of large butterflies in amber, but that these proved to be falsifications, recent European insects like Pieris rapæ, etc., having been enclosed between slabs of amber, which were then fastened together and the edges roughened, all in so clever a manner that one would not suspect them to be spurious. These specimens were manufactured many years ago, and it is not impossible that it is to one of them that Hope refers in 1836, as found in the collection of Mr. Strong, though why he should quote Berendt as authority I cannot discover.