and Rosa, adduced by Mr. Darwin himself; for though the amplest
materials exist for a knowledge of these groups, and the most careful
research has been bestowed upon them, yet the various species have not
thereby been accurately limited and defined so as to satisfy the
majority of botanists. In Mr. Baker's revision of the British Roses,
just published by the Linnaean Society, the author includes under the
single species Rosa canina, no less than twenty-eight named _varieties_,
distinguished by more or less constant characters and often confined to
special localities; and to these are referred about seventy of the
_species_ of Continental and British botanists.
Dr. Hooker seems to have found the same thing in his study of the Arctic
flora. For though he has had much of the accumulated materials of his
predecessors to work upon, he continually expresses himself as unable to
do more than group the numerous and apparently fluctuating forms into
more or less imperfectly defined species. In his paper on the
"Distribution of Arctic Plants," (Trans. Linn. Soc. xxiii., p. 310) Dr.
Hooker says:--"The most able and experienced descriptive botanists vary
in their estimate of the value of the 'specific term' to a much greater
extent than is generally supposed." ... "I think I may safely affirm
that the 'specific term' has three different standard values, all
current in descriptive botany, but each more or less confined to one
class of observers." ... "This is no question of what is right or wrong
as to the real value of the specific term; I believe each is right
according to the standard he assumes as the specific."
Lastly, I will adduce Mr. Bates's researches on the Amazons. During
eleven years he accumulated vast materials, and carefully studied the
variation and distribution of insects. Yet he has shown that many
species of Lepidoptera, which before offered no special difficulties,
are in reality most intricately combined in a tangled web of affinities,
leading by such gradual steps from the slightest and least stable
variations to fixed races and well-marked species, that it is very often
impossible to draw those sharp dividing-lines which it is supposed that
a careful study and full materials will always enable us to do.
These few examples show, I think, that in every department of nature
there occur instances of the instability of specific form, which the
increase of materials aggravates rather than diminishes. And it must be
remembered that the naturalist is rarely likely to err on the side of
imputing greater indefiniteness to species than really exists. There is
a completeness and satisfaction to the mind in defining and limiting
and naming a species, which leads us all to do so whenever we
conscientiously can, and which we know has led many collectors to reject
vague intermediate forms as destroying the symmetry of their cabinets.
We must therefore consider these cases of excessive variation and
instability as being thoroughly well established; and to the objection
that, after all, these cases are but few compared with those in which
species can be limited and defined, and are therefore merely exceptions
to a general rule, I reply that a true law embraces all apparent
exceptions, and that to the great laws of nature there are no real
exceptions--that what appear to be such are equally results of law, and
are often (perhaps indeed always) those very results which are most
important as revealing the true nature and action of the law. It is for
such reasons that naturalists now look upon the study of _varieties_ as
more important than that of well-fixed species. It is in the former that
we see nature still at work, in the very act of producing those
wonderful modifications of form, that endless variety of colour, and
that complicated harmony of relations, which gratify every sense and
give occupation to every faculty of the true lover of nature.
_Variation as specially influenced by Locality._
The phenomena of variation as influenced by locality have not hitherto
received much attention. Botanists, it is true, are acquainted with the
influences of climate, altitude, and other physical conditions, in
modifying the forms and external characteristics of plants; but I am not
aware that any peculiar influence has been traced to locality,
independent of climate. Almost the only case I can find recorded is
mentioned in that repertory of natural-history facts, "The Origin of
Species," viz. that herbaceous groups have a tendency to become arboreal
in islands. In the animal world, I cannot find that any facts have been
pointed out as showing the special influence of locality in giving a
peculiar _facies_ to the several disconnected species that inhabit it.
What I have to adduce on this matter will therefore, I hope, possess
some interest and novelty.
On examining the closely allied species, local forms, and varieties
distributed over the Indian and Malayan regions, I find that larger or
smaller districts, or even single islands, give a special character to
the majority of their Papilionidae. For instance: 1. The species of the
Indian region (Sumatra, Java, and Borneo) are almost invariably smaller
than the allied species inhabiting Celebes and the Moluccas; 2. The
species of New Guinea and Australia are also, though in a less degree,
smaller than the nearest species or varieties of the Moluccas; 3. In the
Moluccas themselves the species of Amboyna are the largest; 4. The
species of Celebes equal or even surpass in size those of Amboyna; 5.
The species and varieties of Celebes possess a striking character in the
form of the anterior wings, different from that of the allied species
and varieties of all the surrounding islands; 6. Tailed species in India
or the Indian region become tailless as they spread eastward through the
archipelago; 7. In Amboyna and Ceram the females of several species are
dull-coloured, while in the adjacent islands they are more brilliant.
_Local variation of Size._--Having preserved the finest and largest
specimens of Butterflies in my own collection, and having always taken
for comparison the largest specimens of the same sex, I believe that the
tables I now give are sufficiently exact. The differences of expanse of
wings are in most cases very great, and are much more conspicuous in the
specimens themselves than on paper. It will be seen that no less than
fourteen Papilionidae inhabiting Celebes and the Moluccas are from
one-third to one-half greater in extent of wing than the allied species
representing them in Java, Sumatra, and Borneo. Six species inhabiting
Amboyna are larger than the closely allied forms of the northern
Moluccas and New Guinea by about one-sixth. These include almost every
case in which closely allied species can be compared.
Species of Papilionidae of the Closely allied species of Java and
Moluccas and Celebes (large). the Indian region (small).
Expanse. Expanse.
Inches. Inches.
Ornithoptera (Helena { O. Pompeus 5.8
Amboyna) 7.6 { O. Amphrisius 6.0
Papilio Adamantius }
(Celebes) 5.8 }
P. Lorquinianus } P. Peranthus 3.8
(Moluccas) 4.8 }
P. Blumei (Celebes) 5.4 P. Brama 4.0
P. Alphenor (Celebes) 4.8 P. Theseus 3.6
P. Gigon (Celebes) 5.4 P. Demolion 4.0
P. Deucalion (Celebes) 4.6 P. Macareus 3.7
P. Agamemnon, var.
(Celebes) 4.4 P. Agamemnon, var. 3.8
P. Eurypilus (Moluccas) 4.0 } P. Jason 3.4
P. Telephus (Celebes) 4.3 }
P. AEgisthus (Moluccas) 4.4 P. Rama 3.2
P. Milon (Celebes) 4.4 P. Sarpedon 3.8
P. Androcles (Celebes) 4.8 P. Antiphates 3.7
P. Polyphontes (Celebes) 4.6 P. Diphilus 3.9
Leptocircus Ennius
(Celebes) 2.0 L. Meges 1.8
Species inhabiting Amboyna Allied species of New Guinea and
(large). the North Moluccas (smaller).
Papilio Ulysses 6.1 { P. Autolycus 5.2
{ P. Telegonus 4.0
P. Polydorus 4.9 P. Leodamas 4.0
P. Deiphobus 6.8 P. Deiphontes 5.8
P. Gambrisius 6.4 { P. Ormenus 5.6
{ P. Tydeus 6.0
P. Codrus 5.1 P. Codrus, var.
papuensis 4.3
Ornithoptera Priamus, Ornithoptera Poseidon,
(male) 8.3 (male) 7.0
_Local variation of Form._--The differences of form are equally clear.
Papilio Pammon everywhere on the continent is tailed in both sexes. In
Java, Sumatra, and Borneo, the closely allied P. Theseus has a very
short tail, or tooth only, in the male, while in the females the tail is
retained. Further east, in Celebes and the South Moluccas, the hardly
separable P. Alphenor has quite lost the tail in the male, while the
female retains it, but in a narrower and less spatulate form. A little
further, in Gilolo, P. Nicanor has completely lost the tail in both
sexes.
Papilio Agamemnon exhibits a somewhat similar series of changes. In
India it is always tailed; in the greater part of the archipelago it has
a very short tail; while far east, in New Guinea and the adjacent
islands, the tail has almost entirely disappeared.
In the Polydorus-group two species, P. Antiphus and P. Diphilus,
inhabiting India and the Indian region, are tailed, while the two which
take their place in the Moluccas, New Guinea, and Australia, P.
Polydorus and P. Leodamas, are destitute of tail, the species furthest
east having lost this ornament the most completely.
Western species, Tailed. Allied Eastern species not Tailed.
Papilio Pammon (India) P. Thesus (Islands) minute tail.
P. Agamemnon, var. (India) P. Agamemnon, var. (Islands).
P. Antiphus (India, Java) P. Polydorus (Moluccas).
P. Diphilus (India, Java) P. Leodamas (New Guinea).
The most conspicuous instance of local modification of form, however, is
exhibited in the island of Celebes, which in this respect, as in some
others, stands alone and isolated in the whole archipelago. Almost every
species of Papilio inhabiting Celebes has the wings of a peculiar shape,
which distinguishes them at a glance from the allied species of every
other island. This peculiarity consists, first, in the upper wings being
generally more elongate and falcate; and secondly, in the costa or
anterior margin being much more curved, and in most instances exhibiting
near the base an abrupt bend or elbow, which in some species is very
conspicuous. This peculiarity is visible, not only when the Celebesian
species are compared with their small-sized allies of Java and Borneo,
but also, and in an almost equal degree, when the large forms of Amboyna
and the Moluccas are the objects of comparison, showing that this is
quite a distinct phenomenon from the difference of size which has just
been pointed out.
In the following Table I have arranged the chief Papilios of Celebes in
the order in which they exhibit this characteristic form most
prominently.
Papilios of Celebes, having the Closely allied Papilios of the
wings falcate or with abruptly surrounding islands, with less
curved costa. wings and slightly falcate curved costa.
1. P. Gigon P. Demolion (Java).
2. P. Pamphylus P. Jason (Sumatra).
3. P. Milon P. Sarpedon (Moluccas, Java).
4. P. Agamemnon, var. P. Agamemnon, var. (Borneo).
5. P. Adamantius P. Peranthus (Java).
6. P. Ascalaphus P. Deiphontes (Gilolo).
7. P. Sataspes P. Helenus (Java).
8. P. Blumei P. Brama (Sumatra).
9. P. Androcles P. Antiphates (Borneo).
10. P. Rhesus P. Aristaeus (Moluccas).
11. P. Theseus, var. (male) P. Thesus (male) (Java).
12. P. Codrus, var. P. Codrus (Moluccas).
13. P. Encelades P. Leucothoe (Malacca).
It thus appears that every species of Papilio exhibits this peculiar
form in a greater or less degree, except one, P. Polyphontes, allied to
P. Diphilus of India and P. Polydorus of the Moluccas. This fact I
shall recur to again, as I think it helps us to understand something of
the causes that may have brought about the phenomenon we are
considering. Neither do the genera Ornithoptera and Leptocircus exhibit
any traces of this peculiar form. In several other families of
Butterflies this characteristic form reappears in a few species. In the
Pieridae the following species, all peculiar to Celebes, exhibit it
distinctly:--
1. Pieris Eperia compared with P. Coronis (Java).
2. Thyca Zebuda " " Thyca Descombesi
(India).
3. T. Rosenbergii " " T. Hyparete (Java).
4. Tachyris Hombronii " " T. Lyncida.
5. T. Lycaste " " T. Lyncida.
6. T. Zarinda " " T. Nero (Malacca).
7. T. Ithome " " T. Nephele.
8. Eronia tritaea " " Eronia Valeria
(Java).
9. Iphias Glaucippe, var. " " Iphias Glaucippe
(Java).
The species of Terias, one or two Pieris, and the genus Callidryas do
not exhibit any perceptible change of form.
In the other families there are but few similar examples. The following
are all that I can find in my collection:--
Cethosia AEole compared with Cethosia Biblis (Java).
Eurhinia megalonice " " Eurhinia Polynice
(Borneo).
Limenitis Limire " " Limenitis Procris
(Java).
Cynthia Arsinoe, var. " " Cynthia Arsinoe (Java,
Sumatra, Borneo)
All these belong to the family of the Nymphalidae. Many other genera of
this family, as Diadema, Adolias, Charaxes, and Cyrestis, as well as the
entire families of the Danaidae, Satyridae, Lycaenidae, and Hesperidae,
present no examples of this peculiar form of the upper wing in the
Celebesian species.
_Local variations of Colour._--In Amboyna and Ceram the female of the
large and handsome Ornithoptera Helena has the large patch on the hind
wings constantly of a pale dull ochre or buff colour, while in the
scarcely distinguishable varieties from the adjacent islands of Bouru
and New Guinea, it is of a golden yellow, hardly inferior in brilliancy
to its colour in the male sex. The female of Ornithoptera Priamus
(inhabiting Amboyna and Ceram exclusively) is of a pale dusky brown
tint, while in all the allied species the same sex is nearly black with
contrasted white markings. As a third example, the female of Papilio
Ulysses has the blue colour obscured by dull and dusky tints, while in
the closely allied species from the surrounding islands, the females are
of almost as brilliant an azure blue as the males. A parallel case to
this is the occurrence, in the small islands of Goram, Matabello, Ke,
and Aru, of several distinct species of Euploea and Diadema, having broad
bands or patches of white, which do not exist in any of the allied
species from the larger islands. These facts seem to indicate some local
influence in modifying colour, as unintelligible and almost as
remarkable as that which has resulted in the modifications of form
previously described.
_Remarks on the facts of Local variation._
The facts now brought forward seem to me of the highest interest. We see
that almost all the species in two important families of the Lepidoptera
(Papilionidae and Pieridae) acquire, in a single island, a characteristic
modification of form distinguishing them from the allied species and
varieties of all the surrounding islands. In other equally extensive
families no such change occurs, except in one or two isolated species.
However we may account for these phenomena, or whether we may be quite
unable to account for them, they furnish, in my opinion, a strong
corroborative testimony in favour of the doctrine of the origin of
species by successive small variations; for we have here slight
varieties, local races, and undoubted species, all modified in exactly
the same manner, indicating plainly a common cause producing identical
results. On the generally received theory of the original distinctness
and permanence of species, we are met by this difficulty: one portion of
these curiously modified forms are admitted to have been produced by
variation and some natural action of local conditions; whilst the other
portion, differing from the former only in degree, and connected with
them by insensible gradations, are said to have possessed this
peculiarity of form at their first creation, or to have derived it from
unknown causes of a totally distinct nature. Is not the _a priori_
evidence in favour of an identity of the causes that have produced such
similar results? and have we not a right to call upon our opponents for
some proofs of their own doctrine, and for an explanation of its
difficulties, instead of their assuming that they are right, and laying
upon us the burthen of disproof?
Let us now see if the facts in question do not themselves furnish some
clue to their explanation. Mr. Bates has shown that certain groups of
butterflies have a defence against insectivorous animals, independent of
swiftness of motion. These are generally very abundant, slow, and weak
fliers, and are more or less the objects of mimicry by other groups,
which thus gain an advantage in a freedom from persecution similar to
that enjoyed by those they resemble. Now the only Papilios which have
not in Celebes acquired the peculiar form of wing, belong to a group
which is imitated both by other species of Papilio and by Moths of the
genus Epicopeia. This group is of weak and slow flight; and we may
therefore fairly conclude that it possesses some means of defence
(probably in a peculiar odour or taste) which saves it from attack. Now
the arched costa and falcate form of wing is generally supposed to give
increased powers of flight, or, as seems to me more probable, greater
facility in making sudden turnings, and thus baffling a pursuer. But the
members of the Polydorus-group (to which belongs the only unchanged
Celebesian Papilio), being already guarded against attack, have no need
of this increased power of wing; and "natural selection" would therefore
have no tendency to produce it. The whole family of Danaidae are in the
same position: they are slow and weak fliers; yet they abound in species
and individuals, and are the objects of mimicry. The Satyridae have also
probably a means of protection--perhaps their keeping always near the
ground and their generally obscure colours; while the Lycaenidae and
Hesperidae may find security in their small size and rapid motions. In
the extensive family of the Nymphalidae, however, we find that several of
the larger species, of comparatively feeble structure, have their wings
modified (Cethosia, Limenitis, Junonia, Cynthia), while the large-bodied
powerful species, which have all an excessively rapid flight, have
exactly the same form of wing in Celebes as in the other islands. On the
whole, therefore, we may say that all the butterflies of rather large
size, conspicuous colours, and not very swift flight have been affected
in the manner described, while the smaller sized and obscure groups, as
well as those which are the objects of mimicry, and also those of
exceedingly swift flight have remained unaffected.
It would thus appear as if there must be (or once have been) in the
island of Celebes, some peculiar enemy to these larger-sized butterflies
which does not exist, or is less abundant, in the surrounding islands.
Increased powers of flight, or rapidity of turning, was advantageous in
baffling this enemy; and the peculiar form of wing necessary to give
this would be readily acquired by the action of "natural selection" on
the slight variations of form that are continually occurring.
Such an enemy one would naturally suppose to be an insectivorous bird;
but it is a remarkable fact that most of the genera of Fly-catchers
of Borneo and Java on the one side (Muscipeta, Philentoma,) and of
the Moluccas on the other (Monarcha, Rhipidura), are almost entirely
absent from Celebes. Their place seems to be supplied by the
Caterpillar-catchers (Graucalus, Campephaga, &c.), of which six or seven
species are known from Celebes and are very numerous in individuals. We
have no positive evidence that these birds pursue butterflies on the
wing, but it is highly probable that they do so when other food is
scarce. Mr. Bates has suggested to me that the larger Dragonflies
(AEshna, &c.) prey upon butterflies; but I did not notice that they were
more abundant in Celebes than elsewhere. However this may be, the fauna
of Celebes is undoubtedly highly peculiar in every department of which
we have any accurate knowledge; and though we may not be able
satisfactorily to trace how it has been effected, there can, I think, be
little doubt that the singular modification in the wings of so many of
the butterflies of that island is an effect of that complicated action
and reaction of all living things upon each other in the struggle for
existence, which continually tends to readjust disturbed relations, and
to bring every species into harmony with the varying conditions of the
surrounding universe.
But even the conjectural explanation now given fails us in the other
cases of local modification. Why the species of the Western islands
should be smaller than those further east,--why those of Amboyna should
exceed in size those of Gilolo and New Guinea--why the tailed species
of India should begin to lose that appendage in the islands, and retain
no trace of it on the borders of the Pacific,--and why, in three
separate cases, the females of Amboyna species should be less gaily
attired than the corresponding females of the surrounding islands,--are
questions which we cannot at present attempt to answer. That they
depend, however, on some general principle is certain, because analogous
facts have been observed in other parts of the world. Mr. Bates informs
me that, in three distinct groups, Papilios which on the Upper Amazon
and in most other parts of South America have spotless upper wings
obtain pale or white spots at Para and on the Lower Amazon; and also
that the AEneas-group of Papilios never have tails in the equatorial
regions and the Amazons valley, but gradually acquire tails in many
cases as they range towards the northern or southern tropic. Even in
Europe we have somewhat similar facts; for the species and varieties of
butterflies peculiar to the island of Sardinia are generally smaller and
more deeply coloured than those of the mainland, and the same has
recently been shown to be the case with the common tortoiseshell
butterfly in the Isle of Man; while Papilio Hospiton, peculiar to the
former island, has lost the tail, which is a prominent feature of the
closely allied P. Machaon.
Facts of a similar nature to those now brought forward would no doubt be
found to occur in other groups of insects, were local faunas carefully
studied in relation to those of the surrounding countries; and they
seem to indicate that climate and other physical causes have, in some
cases, a very powerful effect in modifying specific form and colour, and
thus directly aid in producing the endless variety of nature.
_Mimicry._
Having fully discussed this subject in the preceding essay, I have only
to adduce such illustrations of it, as are furnished by the Eastern
Papilionidae, and to show their bearing upon the phenomena of variation
already mentioned. As in America, so in the Old World, species of
Danaidae are the objects which the other families most often imitate. But
besides these, some genera of Morphidae and one section of the genus
Papilio are also less frequently copied. Many species of Papilio mimic
other species of these three groups so closely that they are
undistinguishable when on the wing; and in every case the pairs which
resemble each other inhabit the same locality.
The following list exhibits the most important and best marked cases of
mimicry which occur among the Papilionidae of the Malayan region and
India:--
Mimickers. Species mimicked. Common habitat.
DANAIDAE.
1. Papilio paradoxa Euploea Midamus } Sumatra, &c.
(male & female) (male & female) }
2. P. Caunus E. Rhadamanthus Borneo and
Sumatra.
3. P. Thule Danais sobrina New Guinea.
4. P. Macareus D. Aglaia Malacca, Java
5. Papilio Agestor Danais Tytia Northern India.
6. P. Idaeoides Hestia Leuconoe Philippines.
7. P. Delessertii Ideopsis daos Penang.
MORPHIDAE.
8. P. Pandion Drusilla bioculata New Guinea
(female)
PAPILIO (POLYDORUS- and COON-groups).