this butterfly was provided (in the female?) with three large spots,
three small spots, and two dots of a vitreous appearance, besides other
light streaks or powdery spots. The three large spots are probably
peculiar, in their present extent, to the female; they consist (Pl.
III, figs. 14, 17,) of one spot in the cell and one in each of the
lower median interspaces; the cellular spot crosses the cell, is
sublunato-quadrate, its exterior edge concave, extending from the origin
of the third superior subcostal nervule to just beyond the second
divarication of the median nervure, being directed in the upper half
of its course toward the base of the second median nervule; the spot
is narrower above than below, the upper half having an outward as well
as upward inclination, the lower margin straight, the interior margin
subsinuate, convex, reaching from midway between the base of the first
and second superior subcostal nervules to just beyond the middle of the
space between the base of the first and second median nervules. The
spot in the lowest median interspace is nearly or quite as large as the
previous, but longitudinal instead of transverse, and as broad as the
interspace; excepting for a little spur above on the inner side, which
runs a little way toward the base, the centre of the spot would lie just
below the second divarication of the median nervure, but by means of this
slight spur the spot extends baseward half way from the second to the
first divarication of the median nervure; at the outer extremity the spot
terminates squarely and next the lowest median nervule is two-sevenths
the length of that vein. The spot in the middle median interspace is much
smaller, subtriangular, filling the whole breadth of the interspace,
half as long again as broad, its inner tapering extremity situated just
below the final divarication of the median nervure. The three small spots
in the lower three subcostal nervules are seated one above the other,
their inner margins on a line and nearly at right angles to the costal
margin; they are quadrate and increase slightly in size below, the upper
one being square, the lower longitudinally oblong; they are situated
midway between the discoidal spot and the apex of the wing. The two dots
are situated one just above the other in the middle of the upper median
and subcosto-median interspaces, midway between the spot in the lower
subcostal interspace and the outer border; the lower is slightly the
larger, but not more than one-fourth the size of the uppermost subcostal
spot. Seated upon the submedian nervure, its centre below the outer edge
of the lower median spot, is a pale, powdery spot, twice as long as broad
and about one-third the width of the interspace; outwardly it merges
into the ground color; there are other pale spaces in the wing, looking
somewhat as if due to attrition; especially in the cell on either side of
the discoidal spot, at the extreme base of the lower median interspace,
and along the lower border of the medio-submedian interspace. Length of
wing, 15·75mm., length of inner border, 9·5mm.; breadth of wing across
the middle, 7·25mm., breadth of wing across outer margin, 9·5mm..
Tertiaries of Aix, Provence, France. Museum of the City of Marseilles.
COMPARATIVE AGE OF FOSSIL BUTTERFLIES.
All the well determined fossil butterflies come from one of three
localities, Aix, Rott and Radoboj, all belonging to the tertiaries of
Europe. Others are reported, as will be seen further on, to have been
found in Prussian amber; and it is not in the least improbable that they
have been or may be. These would be of about the same age as the oldest
of the others, those of Aix. Of the Aix fossils, which belong to the
upper Eocene, or to speak more definitely, the Ligurian, _Neorinopis
sepulta_, _Lethites Reynesii_, _Thaites Ruminiana_ and _Pamphilites
abdita_ (the first described by Boisduval, the rest by myself) come
from the calcareous marls of the gypsum quarries, the only bed in which
insects had been found when visited by Messrs. Murchison and Lyell in
1829. _Coliates Proserpina_, however, described here for the first time,
was taken from strata beneath these, and therefore, at least until we
have more precise knowledge concerning the remains of butterfly larvæ in
amber, may be considered the oldest known butterfly. Count de Saporta
writes me concerning this fossil, the discovery of which is due to him,
as follows:—“Cette empreinte ne provient pas des platrières même, c’est
à dire des galeries qui servent à l’exploitation du Gypse; mais d’une
assise ou groupe de couches immédiatement inférieure. Vous verrez cette
provenance indiquée pour un grand nombre de mes espèces; dans ce cas,
elles ne proviennent par des ouvriers mais je les ai recueillies moi même
en suivant les lits sur les points où ils affleurent au dehors.”
The next in order, approaching recent times, are the lignite beds of Rott
in the basin of the Rhine, which belong to the Aquitanian or the upper
part of the lower Miocene. _Thanatites vetula_ (described by Hayden) is
the only butterfly known from this division of the Tertiaries.
The most recent beds containing fossil butterflies are the lacustrine
deposits of Radoboj in Croatia, Austria. These belong to the Mayencian or
lower portion of the middle Miocene, and have furnished _Eugonia atava_,
_Mylothrites Pluto_, another fragment possibly referable to Mylothrites,
and _Pontia Freyeri_, all described by Heer. Two of the genera of these
more recent beds contain representatives now living in the same region;
but none of the older beds have yet furnished butterflies referable to
modern genera.
It is rather extraordinary that the upper Miocene beds of Œningen,
Bavaria, which, if we except the amber, have furnished almost more
insects than all the other beds of fossil insects of the world together,
and which are more recent than any of those in which butterflies have
been found, have yielded scarcely any remains of Lepidoptera (one
species) and none whatever of butterflies.
PROBABLE FOOD-PLANTS OF TERTIARY CATERPILLARS.
Of the five butterflies from Aix, two belong to the Oreades (_Neorinopis
sepulta_ and _Lethites Reynesii_) the food of whose caterpillars at
the present epoch has invariably been found to be either Gramineæ or,
occasionally, Cyperaceæ. Both of these groups are present in the deposits
of Aix, the former being represented by ten species of Poacites, and the
latter by a Cyperites;[AG] and it is in the highest degree probable that
these formed the sustenance of the Oreades of that epoch. A third species
(_Pamphilites abdita_) belongs to the Astyci, a group whose principal
food is the same family of plants, Gramineæ, although some species have
been found also upon Althea, Malva and Lavatera (Malvaceæ), Trifolium,
Coronilla and ?Lespedeza (Leguminosæ), Plantago (Plantaginaceæ), and
Maranta (Scitamineæ). Of these families the Leguminosæ only are found
at Aix, and in abundance, even including a plant doubtfully referred to
Trifolium. It is, however, far more probable that Pamphilites lived upon
grasses; and it is not a little strange that the Gramineæ, the probable
food-plants of three of the five butterflies known from that fauna, were
among the rarest of the plants; that is, their proportion to the whole
phanerogamic flora was about the same as now obtains in New Guinea
or New Grenada, countries the least favored in this respect.[AH] The
proportion of the Gramineæ and Cyperaceæ to the whole of the Phanerogamia
in Europe of to-day is, probably, about the same as in the United States
(more than seventeen per cent.) and much greater than in the East
Indies. The limited number of known fossil butterflies does not give
great weight to any general considerations based upon them, but it may
at least be worth while to remark that Aix, in Eocene times, had, in the
point referred to, an assemblage of plants much better comparable with
the East Indian flora of the present day than with the modern European
flora, the proportion of known Gramineæ, etc., to the Phanerogamia being
five per cent., while the proportion of its grass-feeding butterflies to
the other rhopalocerous Lepidoptera is sixty per cent. To judge simply
by the catalogue of the East India Museum, the only authority upon East
Indian butterflies extant, the present proportion of gramnivorous to
non-gramnivorous butterflies is as 1: 5·2, while in Europe it is as 1:
3. Eocene Aix, then, had a European proportion of Satyrids, composed,
as will be seen, of species of an Indian aspect, feeding upon plants
essentially temperate, but, as in tropical countries, numerically
unimportant.
The Danai, to which the fourth species from Aix (_Coliates Proserpina_)
belongs, feed almost exclusively upon Leguminosæ, and these have recently
been found in great abundance at Aix. Count de Saporta enumerates one
species each of ?Trifolium, Caragana, Ervites, Sophora, Micropodium,
Cercis and Gleditschia, two of Phaseolites and six of Cæsalpinites,
belonging to the Papilionaceæ, besides nine Acacias and a Mimosa of the
Mimoseæ, and four species of uncertain relations; making a series larger
than he has found in any other family.[AI]
Of these, two species of Phaseolites, one of Sophora, eight of Acacia
and two of Leguminosites are specified as coming from the lower beds,
where Coliates itself is found. But Coliates is most closely allied, as
we have said, to a group of Indian forms, and the food plants of their
caterpillars is almost wholly unknown. A species of Delias, however,
to which genus Coliates has been specially compared, is stated to
feed, not upon a leguminous plant, but upon Dioscorea, one of the Yam
family; and the presence in Aix of a species of a closely allied group,
_Smilax rotundiloba_ Sap., is announced by Count de Saporta. It is not
improbable, therefore, that _Smilax rotundiloba_ was the food-plant of
the larva of _Coliates Proserpina_.[AJ]
The fifth Aix species is _Thaites Ruminiana_. It is most nearly allied
to Thais of the present day, though it bears certain relations, as we
have seen, to neighboring genera. Thais feeds principally at least
upon Aristolochia[AK] and so, too, do Ornithoptera, Archon and some
genera of swallow-tails; indeed, this seems to be a favorite food-plant
with insects of this character. Parnassius, however, feeds on Sedum,
Telephium, Sempervivum and Corydalis, especially on the first-named, one
of the Crassulaceæ; but nothing very closely allied to this is specified
by Saporta from Aix; neither, also is Aristolochia, but it has been
found not only in Radoboj[AL] in the Mayencian, but also, according to
Heer, at Hohe Rhonen in Switzerland, which belongs to the Aquitanian,
and has at least one plant (_Laurus primigenia_ Ung.) in common with
Aix. It seems, therefore, highly probable that either _Aristolochia
nervosa_ Heer, _A. Aesculapi_ Heer, or a distinct species of the genus
will yet be discovered at Aix,[AM] and may then be considered, as with
little question, the food-plant of _Thaites Ruminiana_. If it be deemed
hazardous to venture such an opinion, attention is called to the two
following passages; the first is from the introduction to Heer’s paper on
the fossil insects of Aix:[AN] “Dass indessen auch Weiden oder Pappeln
[Populus] sich vorhanden, dürften der Bythoscopus muscarius und die
Aphrophora spumifera [Homoptera] anzeigen, deren analoge lebende Arten
besonders auf den Blättern und Zweigen dieser Bäume sich umhertreiben.”
The second is a note in the errata to the translation of Heer’s work on
the Climate and Vegetation of the Tertiaries[AO] by Gaudin: “Le Poacites
ciliatus Sap. n’est pas une glume de Graminée, mais plutôt une bractée
ciliée de Peuplier.… Elle doit être probablement rapprochée d’une
empreinte … provenant des mêmes couches et qui se rapporte également au
genre Populus. Les organes voisins de ceux du Pop. Euphratica Oliv. dans
la nature actuelle dénotent l’existence, à l’époque des gypses d’Aix,
d’une espèce de Peuplier dont les feuilles sont encore inconnues, comme
celles de l’Alnus cryptophylla Sap., mais que M. Heer avait indiqué
d’avance, en se fondant sur l’observation d’un insecte fossile, le
Bythoscopus muscarius! Nouvelle preuve du secours que peuvent se prêter
en paléontologie les diverses branches de l’histoire naturelle.”
The single species from Rott, _Thanatites vetula_, is closely allied to
the modern Thanaos, whose species are numerous and feed upon a variety
of plants, belonging to the families Cruciferæ, Leguminosæ, Umbelliferæ,
Cupuliferæ, Betulaceæ and Salicaceæ. Most of the genera belonging to
its tribe feed upon Leguminosæ, and these are the usual food plants of
the species Thanaos also; whence it is probable that Thanatites had a
similar taste. Now in the very beds of Rott, in which this butterfly was
found, occur species of Betula, Salix and Populus, with numerous Querci
and no less than eleven genera of Leguminosæ, mostly belonging to the
Papilionaceæ; they are Templetonia (1 species), Robinia (2), Colutea
(1), Phaseolites (2), Sphinctolobium (1), Dalbergia (1), Hæmatoxylon
(2), Gleditschia (2), Cassia (3), Ceratonia (1), and Acacia (2). It is
probably among these, and perhaps with greatest probability among the
species of Hæmatoxylon and Gleditschia, that the food plant of Thanatites
must be sought. Should leaves be found, in which a portion is bent over
as if to form a nest, they should be submitted to the scrutiny of some
one familiar with the larval habitations of _Thanaos Tages_; and should
traces of silken fastenings be found in connection with them, or the
marks of nibbling at the edges, the plant to which they belong may be
considered with strong probability as the food of _Thanatites vetula_.
The only butterfly found at Radoboj belonging to an extinct genus is
_Mylothrites Pluto_, and this is a member of the same general group as
Coliates, and feeds probably upon Leguminosæ; for it is not so closely
allied to Delias as Coliates is, but is more nearly related to Hebomoia,
one of whose species, found in the East Indias, feeds upon Capparis.[AP]
One species of Phaseolites, one of Sophora and four of Cassia, namely:
_C. hyberborea_ Ung., _C. phaseolites_ Ung., _C. lignitum_ Ung., and _C.
ambigua_ Ung., are recorded from Radoboj, and as Cassia is a favorite
food plant among the larger species of Danai at the present day, we
may fairly presume one of these Cassiæ to have afforded nourishment
to _Mylothrites Pluto_. Moreover, no less than thirty-one species of
Leguminosæ in general, or between a ninth and a tenth of the whole known
flora, are given by von Ettingshausen as occurring in Radoboj; so that in
any case our Mylothrites must have found abundance of palatable food.
The food of _Pontia Freyeri_ is doubtful. All the living species of the
genus so far as known, feed upon Cruciferæ; within this family they do
not seem to be at all particular, making use of a large number of genera,
but in only a single instance are they known to attack the leaves of a
genus (Reseda) belonging to an adjoining family. Cruciferæ, however, are
excessively rare in the tertiaries of Europe, two species only being
recorded, and this from the comparatively recent beds of Œningen. This
is unquestionably due simply to the nature of the plants themselves,
which scarcely could leave any trace of their existence; the almost
complete absence of the herbaceous families of plants, even in the later
tertiaries, is doubtless due to this fact. The plants nearest related to
the Cruciferæ found near the horizon of _Pontia Freyeri_ are a species
of Nelumbium from Günzbourg in the Mayencian, and of Terminalia (_T.
radobojensis_ Ung.)—one of the Calycifloræ, from Radoboj itself. Perhaps
in the absence of better evidence we may provisionally consider the
latter to have been the food plant of _P. Freyeri_.
A single Radoboj species remains, _Eugonia atava_. The recent species of
Eugonia feed particularly on Salix, Populus and Betula; also upon Ulmus,
and occasionally on Ribes, and even on Hippophae. The first three seem
however to be their proper food; and since the tertiaries of Radoboj
contain fossils of all these genera, we need look no farther. There
are specified: _Salix apollinis_ Ung., sp., _Populus latior_ Br., _P.
mutabilis_ Heer., _P. Heliadum_ Ung., _Betula Dryadum_ Brongn. and _B.
prisca_ Ett. Three species of Ulmus are also recorded from the same place.
Excepting in a single case, there is then no difficulty in finding, in
the very hods in which the butterflies occur, remains of plants, which
in all probability served them as food during the larval stage; and even
in this single instance, a plant not far removed from those upon which
species of the genus now feed, occurs in the same strata.
PRESENT DISTRIBUTION OF BUTTERFLIES MOST NEARLY ALLIED TO FOSSIL SPECIES.
To discuss this question properly we must consider the butterflies of
each geological horizon separately.
BUTTERFLIES OF THE LIGURIAN (Upper Eocene).
The nearest living ally of _Neorinopis sepulta_ is, with little doubt,
_Neorina Lowi_, which, like the other members of the genus, is found in
the Indo-Malayan region. The same is strictly true of the species of
Zophoessa, Debis and Lethe, with which we have been obliged to compare
this fossil. Cœlites has also been used in comparison, and most of
the species of this group belong to the same region, although one is
described by Felder from Celebes on the confines of the Austro-Malayan
region. We have also pointed out (as Butler has done, but in incorrect
points) its relation to Antirrhæa, a Brazilian genus, but this is too
distant to be given much weight. The closest allies of _N. sepulta_ are
to be found in the Indo-Malayan region.
The same is true, but not to so striking a degree, of _Lethites
Reynesii_. We have compared this also to Debis, Lethe and Neorina, and
especially to the two former; and all three of these genera, which are
certainly its nearest allies, are strictly confined to the Indo-Malayan
region. It is, however, also related, but in a secondary degree, to
Enodia, Cercyonis and Maniola, which are genera appertaining to the north
temperate zone of both hemispheres.
_Coliates Proserpina_ finds its nearest living representatives in the
genus Delias, which also is strictly confined to the Indo-Malayan
region. Thyca and Prioneris are closely related, the latter of which
is limited to the same district and the former to the Indo-Malayan and
Austro-Malayan regions.
_Thaites Ruminiana_ is represented in recent times by the genus Thais,
which is confined to the Mediterranean district, within which Aix
lies. An allied genus, Archon, is also restricted to the same region.
Sericinus, however, and Eurycus, with which we have been obliged to
compare it in many points, are found only in the East, the former in
China, the latter in Australia; while on the other hand, Parnassius, a
genus it quite as much resembles, is limited to alpine and subarctic
regions of the northern hemisphere.
The relations of _Pamphilites abdita_ are very different. I have searched
carefully for very closely allied forms among East Indian Urbicolæ;
but, while it doubtless is not far removed from some of them, its more
intimate relationships are certainly with insects from tropical America
and especially with Pansydia and Carystus.
Three out of the five Aix butterflies, therefore, find their nearest
living allies in the Indo-Malayan region, one is most closely related to
forms now found in tropical America and one is at home in its own resting
place.
BUTTERFLIES OF THE AQUITANIAN (Lower Miocene).
_Thanatites vetula_ is the only butterfly yet found from this horizon,
and this is closely related to Thanaos, a genus belonging to the north
temperate zones of both hemispheres, but vastly more developed in the
new world, which has at least four times as many species as the old,
some of them extending into the subtropical regions. The genera adjacent
to Thanaos are purely American, although tropical or subtropical, and
therefore the Aquitanian butterfly looks toward subtropical North America
for its relatives of the present day.
BUTTERFLIES OF THE MAYENCIAN (Middle Miocene).
Only a single one of these butterflies, _Mylothrites Pluto_, belongs to
an extinct genus. Its nearest living representatives are to be looked
for in the genera Mylothris and Hebomoia, the former of which finds its
highest development in torrid Africa, while the latter is confined to the
Indo-Malayan and Austro-Malayan regions.
The other two belong to modern genera, Eugonia (_E. atava_) and Pontia
(_P. Freyeri_). These two genera are very similar in their distribution,
spreading, like Thanaos, above referred to, over the north temperate
regions of both hemispheres. Eugonia, however, is represented equally in
Europe and America, while Pontia is considerably richer in species in
the Old World than in the New; yet when we look into the distribution
of the neighboring genera we shall find a result somewhat similar to
the case of Thanaos. Taking into consideration, in the one case, the
present distribution of the genera Hypanartia, Polygonia, Papilio and
Hamadryas,[AQ] and on the other of Neophasia, Tatocheila and Leptophobia,
we shall find that the largest development of these groups of genera has
been in the New World rather than in the Old, but in those parts of the
New World which lie on the tropical confines of the temperate zone.
Two of the more recent species of fossil butterflies are therefore at
home where they are found, although the present development of the group
of genera to which they belong finds its fullest expression in America;
while the third species follows most of those from the lower tertiaries
in seeking its allies of to-day in the tropics of the old world.
* * * * *
Undoubtedly the material at our disposal is, as we have already remarked,
far too meagre to present any generalities of importance, so long as they
are unsupported by external proof. This aid we can claim in considering
the facts we have presented concerning the present distribution of the
genera of butterflies most nearly allied to those once living in the
neighborhood of Aix. The careful researches of Count Saporta upon the
rich flora of this region at the same epoch, points to very nearly the
same results as are here indicated. In his _Examen des flores tertiaires
de Provence_,[AR] when writing of the characteristics of the Aix flora,
Count Saporta says (page 150) that about one-fifth of the families
represented in it are now strangers to Europe; that fifty-one genera
have an exotic and more or less tropical aspect, and that forty out of
seventy-four, or about one-half, if not exclusively tropical, inhabit
the warmer parts of southern regions, or, in small numbers, temperate
extra-European countries. The result is still more striking, if species
are considered, of which there are at least eighty whose individual
analogy with living species is sufficiently clear to yield results of
great probability. “De ces espèces,” to use his own words, “12 seulement
correspondent à des espèces de l’Europe moyenne, 6 à des espèces de
l’Europe méridionale, 18 en tout. Les espèces correspondant à des formes
de l’Amérique septentrionale ou des régions élevées de l’Amérique
tropicale, sont au nombre de 10; celles qui répondent à des formes de
l’Amérique tropicale s’élèvent à 9 …; 3 correspondent à des espèces
du Cap et 2 à des espèces des îles Atlantiques et de la Barbarie; 14
représentent des formes particulières aux Indes ou aux îles de l’Archipel
indien et 30, enfin, correspondent à des formes australiennes. Le groupe
australien est donc le plus considérable, si on les prend isolement. En
les réunnissant, on voit que sur les 80 et quelques espèces, 28 à 30
seulement correspondent à des formes habitant aujourd’hui l’Europe et
l’Amérique du Nord, en y comprenant même les parties méridionales de ces
continents; tandis que 57 au moins, soit 60 en nombre rond, représentent
des formes tropicales ou subtropicales, et dans ce nombre 40 au moins,
c’est-a-dire la moitié du nombre total se rapportent au Cap, aux [151]
Indes orientales où à l’Australie; de sorte que le caractère dominant de
cette flore est encore Austro-indien, quoique dans une proportion déjà
décroissante par rapport à l’âge précédant.”