female)
10. P. Theseus, var. P. Antiphus Sumatra, Borneo.
(female)
11. P. Theseus, var. P. Diphilus Sumatra, Java.
(female)
12. P. Memnon, var. P. Coon Sumatra.
(Achates, female)
13. P. Androgeus, var. P. Doubledayi Northern India.
(Achates, female)
14. P. Oenomaus P. Liris Timor.
(female)
We have, therefore, fourteen species or marked varieties of Papilio,
which so closely resemble species of other groups in their respective
localities, that it is not possible to impute the resemblance to
accident. The first two in the list (Papilio paradoxa and P. Caunus) are
so exactly like Euploea Midamus and E. Rhadamanthus on the wing, that
although they fly very slowly, I was quite unable to distinguish them.
The first is a very interesting case, because the male and female differ
considerably, and each mimics the corresponding sex of the Euploea. A
new species of Papilio which I discovered in New Guinea resembles Danais
sobrina, from the same country, just as Papilio Marcareus resembles
Danais Aglaia in Malacca, and (according to Dr. Horsfield's figure)
still more closely in Java. The Indian Papilio Agestor closely imitates
Danais Tytia, which has quite a different style of colouring from the
preceding; and the extraordinary Papilio Idaeoides from the Philippine
Islands, must, when on the wing, perfectly resemble the Hestia Leuconoe
of the same region, as also does the Papilio Delessertii imitate the
Ideopsis daos from Penang. Now in every one of these cases the Papilios
are very scarce, while the Danaidae which they resemble are exceedingly
abundant--most of them swarming so as to be a positive nuisance to the
collecting entomologist by continually hovering before him when he is in
search of newer and more varied captures. Every garden, every roadside,
the suburbs of every village are full of them, indicating very clearly
that their life is an easy one, and that they are free from persecution
by the foes which keep down the population of less favoured races. This
superabundant population has been shown by Mr. Bates to be a general
characteristic of all American groups and species which are objects of
mimicry; and it is interesting to find his observations confirmed by
examples on the other side of the globe.
The remarkable genus Drusilla, a group of pale-coloured butterflies,
more or less adorned with ocellate spots, is also the object of mimicry
by three distinct genera (Melanitis, Hyantis, and Papilio). These
insects, like the Danaidae, are abundant in individuals, have a very
weak and slow flight, and do not seek concealment, or appear to have any
means of protection from insectivorous creatures. It is natural to
conclude, therefore, that they have some hidden property which saves
them from attack; and it is easy to see that when any other insects, by
what we call accidental variation, come more or less remotely to
resemble them, the latter will share to some extent in their immunity.
An extraordinary dimorphic form of the female of Papilio Ormenus has
come to resemble the Drusillas sufficiently to be taken for one of that
group at a little distance; and it is curious that I captured one of
these Papilios in the Aru Islands hovering along the ground, and
settling on it occasionally, just as it is the habit of the Drusillas to
do. The resemblance in this case is only general; but this form of
Papilio varies much, and there is therefore material for natural
selection to act upon, so as ultimately to produce a copy as exact as in
the other cases.
The eastern Papilios allied to Polydorus, Coon, and Philoxenus, form a
natural section of the genus resembling, in many respects, the
AEneas-group of South America, which they may be said to represent in the
East. Like them, they are forest insects, have a low and weak flight,
and in their favourite localities are rather abundant in individuals;
and like them, too, they are the objects of mimicry. We may conclude,
therefore, that they possess some hidden means of protection, which
makes it useful to other insects to be mistaken for them.
The Papilios which resemble them belong to a very distinct section of
the genus, in which the sexes differ greatly; and it is those females
only which differ most from the males, and which have already been
alluded to as exhibiting instances of dimorphism, which resemble species
of the other group.
The resemblance of P. Romulus to P. Hector is, in some specimens, very
considerable, and has led to the two species being placed following each
other in the British Museum Catalogues and by Mr. E. Doubleday. I have
shown, however, that P. Romulus is probably a dimorphic form of the
female P. Pammon, and belongs to a distinct section of the genus.
The next pair, Papilio Theseus, and P. Antiphus, have been united as one
species both by De Haan and in the British Museum Catalogues. The
ordinary variety of P. Theseus found in Java almost as nearly resembles
P. Diphilus, inhabiting the same country. The most interesting case,
however, is the extreme female form of P. Memnon (figured by Cramer
under the name of P. Achates), which has acquired the general form and
markings of P. Coon, an insect which differs from the ordinary male P.
Memnon, as much as any two species which can be chosen in this extensive
and highly varied genus; and, as if to show that this resemblance is not
accidental, but is the result of law, when in India we find a species
closely allied to P. Coon, but with red instead of yellow spots (P.
Doubledayi), the corresponding variety of P. Androgeus (P. Achates,
Cramer, 182, A, B,) has acquired exactly the same peculiarity of having
red spots instead of yellow. Lastly, in the island of Timor, the female
of P. Oenomaus (a species allied to P. Memnon) resembles so closely P.
Liris (one of the Polydorus-group), that the two, which were often seen
flying together, could only be distinguished by a minute comparison
after being captured.
The last six cases of mimicry are especially instructive, because they
seem to indicate one of the processes by which dimorphic forms have been
produced. When, as in these cases, one sex differs much from the other,
and varies greatly itself, it may happen that occasionally individual
variations will occur having a distant resemblance to groups which are
the objects of mimicry, and which it is therefore advantageous to
resemble. Such a variety will have a better chance of preservation; the
individuals possessing it will be multiplied; and their accidental
likeness to the favoured group will be rendered permanent by hereditary
transmission, and, each successive variation which increases the
resemblance being preserved, and all variations departing from the
favoured type having less chance of preservation, there will in time
result those singular cases of two or more isolated and fixed forms,
bound together by that intimate relationship which constitutes them the
sexes of a single species. The reason why the females are more subject
to this kind of modification than the males is, probably, that their
slower flight, when laden with eggs, and their exposure to attack while
in the act of depositing their eggs upon leaves, render it especially
advantageous for them to have some additional protection. This they at
once obtain by acquiring a resemblance to other species which, from
whatever cause, enjoy a comparative immunity from persecution.
_Concluding remarks on Variation in Lepidoptera._
This summary of the more interesting phenomena of variation presented by
the eastern Papilionidae is, I think, sufficient to substantiate my
position, that the Lepidoptera are a group that offer especial
facilities for such inquiries; and it will also show that they have
undergone an amount of special adaptive modification rarely equalled
among the more highly organized animals. And, among the Lepidoptera, the
great and pre-eminently tropical families of Papilionidae and Danaidae
seem to be those in which complicated adaptations to the surrounding
organic and inorganic universe have been most completely developed,
offering in this respect a striking analogy to the equally
extraordinary, though totally different, adaptations which present
themselves in the Orchideae, the only family of plants in which mimicry
of other organisms appears to play any important part, and the only one
in which cases of conspicuous polymorphism occur; for as such we must
class the male, female, and hermaphrodite forms of Catasetum
tridentatum, which differ so greatly in form and structure that they
were long considered to belong to three distinct genera.
_Arrangement and Geographical Distribution of the Malayan Papilionidae_.
_Arrangement._--Although the species of Papilionidae inhabiting the
Malayan region are very numerous, they all belong to three out of the
nine genera into which the family is divided. One of the remaining
genera (Eurycus) is restricted to Australia, and another (Teinopalpus)
to the Himalayan Mountains, while no less than four (Parnassius,
Doritis, Thais, and Sericinus) are confined to Southern Europe and to
the mountain-ranges of the Palaearctic region.
The genera Ornithoptera and Leptocircus are highly characteristic of
Malayan entomology, but are uniform in character and of small extent.
The genus Papilio, on the other hand, presents a great variety of forms,
and is so richly represented in the Malay Islands, that more than
one-fourth of all the known species are found there. It becomes
necessary, therefore, to divide this genus into natural groups before we
can successfully study its geographical distribution.
Owing principally to Dr. Horsfield's observations in Java, we are
acquainted with a considerable number of the larvae of Papilios; and
these furnish good characters for the primary division of the genus into
natural groups. The manner in which the hinder wings are plaited or
folded back at the abdominal margin, the size of the anal valves, the
structure of the antennae, and the form of the wings are also of much
service, as well as the character of the flight and the style of
colouration. Using these characters, I divide the Malayan Papilios into
four sections, and seventeen groups, as follows:--
Genus ORNITHOPTERA.
a. Priamus-group. } Black and Green.
c. Brookeanus-group.}
b. Pompeus-group. Black and yellow.
Genus PAPILIO.
A. Larvae short, thick, with numerous fleshy tubercles;
of a purplish colour.
a. Nox-group. Abdominal fold in male very large;
anal valves small, but swollen; antennae moderate;
wings entire, or tailed; includes the Indian
Philoxenus-group.
b. Coon-group. Abdominal fold in male small; anal
valves small, but swollen; antennae moderate;
wings tailed.
c. Polydorus-group. Abdominal fold in male small,
or none; anal valves small or obsolete, hairy;
wings tailed or entire.
B. Larvae with third segment swollen, transversely or
obliquely banded; pupa much bent. Imago with
abdominal margin in male plaited, but not reflexed;
body weak; antennae long; wings much
dilated, often tailed.
d. Ulysses-group.
{Protenor-group (Indian) is
e. Peranthus-group. {somewhat intermediate between
f. Memnon-group. {these, and is nearest
{to the Nox-group.
g. Helenus-group.
h. Erectheus-group.
i. Pammon-group.
k. Demolion-group.
C. Larvae subcylindrical, variously coloured. Imago with
abdominal margin in male plaited, but not reflexed;
body weak; antennae short, with a thick
curved club; wings entire.
l. Erithonius-group. Sexes alike, larva and pupa
something like those of P. Demolion.
m. Paradoxa-group. Sexes different.
n. Dissimilis-group. Sexes alike; larva bright-coloured;
pupa straight, cylindric.
D. Larvae elongate, attenuate behind, and often bifid, with
lateral and oblique pale stripes, green. Imago
with the abdominal margin in male reflexed,
woolly or hairy within; anal valves small, hairy;
antennae short, stout; body stout.
o. Macareus-group. Hind wings entire.
p. Antiphates-group. Hind wings much tailed (swallow-tails).
q. Eurypylus-group. Hind wings elongate or tailed.
Genus LEPTOCIRCUS.
Making, in all, twenty distinct groups of Malayan Papilionidae.
The first section of the genus Papilio (A) comprises insects which,
though differing considerably in structure, having much general
resemblance. They all have a weak, low flight, frequent the most
luxuriant forest-districts, seem to love the shade, and are the objects
of mimicry by other Papilios.
Section B consists of weak-bodied, large-winged insects, with an
irregular wavering flight, and which, when resting on foliage, often
expand the wings, which the species of the other sections rarely or
never do. They are the most conspicuous and striking of eastern
Butterflies.
Section C consists of much weaker and slower-flying insects, often
resembling in their flight, as well as in their colours, species of
Danaidae.
Section D contains the strongest-bodied and most swift-flying of the
genus. They love sunlight, and frequent the borders of streams and the
edges of puddles, where they gather together in swarms consisting of
several species, greedily sucking up the moisture, and, when disturbed,
circling round in the air, or flying high and with great strength and
rapidity.
_Geographical Distribution._--One hundred and thirty species of Malayan
Papilionidae are now known within the district extending from the Malay
peninsula, on the north-west, to Woodlark Island, near New Guinea, on
the south-east.
The exceeding richness of the Malayan region in these fine insects is
seen by comparing the number of species found in the different tropical
regions of the earth. From all Africa only 33 species of Papilio are
known; but as several are still undescribed in collections, we may raise
their number to about 40. In all tropical Asia there are at present
described only 65 species, and I have seen in collections but two or
three which have not yet been named. In South America, south of Panama,
there are 150 species, or about one-seventh more than are yet known from
the Malayan region; but the area of the two countries is very different;
for while South America (even excluding Patagonia) contains 5,000,000
square miles, a line encircling the whole of the Malayan islands would
only include an area of 2,700,000 square miles, of which the land-area
would be about 1,000,000 square miles. This superior richness is partly
real and partly apparent. The breaking up of a district into small
isolated portions, as in an archipelago, seems highly favourable to the
segregation and perpetuation of local peculiarities in certain groups;
so that a species which on a continent might have a wide range, and
whose local forms, if any, would be so connected together that it would
be impossible to separate them, may become by isolation reduced to a
number of such clearly defined and constant forms that we are obliged to
count them as species. From this point of view, therefore, the greater
proportionate number of Malayan species may be considered as apparent
only. Its true superiority is shown, on the other hand, by the
possession of three genera and twenty groups of Papilionidae against a
single genus and eight groups in South America, and also by the much
greater average size of the Malayan species. In most other families,
however, the reverse is the case, the South American Nymphalidae,
Satyridae, and Erycinidae far surpassing those of the East in number,
variety, and beauty.
The following list, exhibiting the range and distribution of each group,
will enable us to study more easily their internal and external
relations.
_Range of the Groups of Malayan Papilionidae._
Ornithoptera.
1. Priamus-group. Moluccas to Woodlark Island 5 species.
2. Pompeus-group. Himalayas to New Guinea,
(Celebes, maximum) 11"
3. Brookeana-group. Sumatra and Borneo 1"
Papilio.
4. Nox-group. North India, Java, and Philippines 5 species
5. Coon-group. North India to Java 2"
6. Polydorus-group. India to New Guinea
and Pacific 7"
7. Ulysses-group. Celebes to New Caledonia 4"
8. Peranthus-group. India to Timor and
Moluccas (India, maximum) 9"
9. Memnon-group. India to Timor and Moluccas
(Java, maximum) 10"
10. Helenus-group. Africa and India to New
Guinea 11"
11. Pammon-group. India to Pacific and Australia 9"
12. Erectheus-group. Celebes to Australia 2"
13. Demolion-group. India to Celebes 2"
14. Erithonius-group. Africa, India, Australia 1"
15. Paradoxa-group. India to Java (Borneo,
maximum) 5"
16. Dissimilis-group. India to Timor (India,
maximum) 2"
17. Macareus-group. India to New Guinea 10"
18. Antiphates-group. Widely distributed 8"
19. Eurypylus-group. India to Australia 15"
Leptocircus.
20. Leptocircus-group. India to Celebes 4"
This Table shows the great affinity of the Malayan with the Indian
Papilionidae, only three out of the twenty groups ranging beyond, into
Africa, Europe, or America. The limitation of groups to the Indo-Malayan
or Austro-Malayan divisions of the archipelago, which is so well marked
in the higher animals, is much less conspicuous in insects, but is shown
in some degree by the Papilionidae. The following groups are either
almost or entirely restricted to one portion of the archipelago:--
_Indo-Malayan Region._ _Austro-Malayan Region._
Nox-group. Priamus-group.
Coon-group. Ulysses-group.
Macareus-group (nearly). Erechtheus-group.
Paradoxa-group.
Dissimilis-group (nearly).
Brookeanus-group.
LEPTOCIRCUS (genus).
The remaining groups, which range over the whole archipelago, are, in
many cases, insects of very powerful flight, or they frequent open
places and the sea-beach, and are thus more likely to get blown from
island to island. The fact that three such characteristic groups as
those of Priamus, Ulysses, and Erechtheus are strictly limited to the
Australian region of the archipelago, while five other groups are with
equal strictness confined to the Indian region, is a strong
corroboration of that division which has been founded almost entirely on
the distribution of Mammalia and Birds.
If the various Malayan islands have undergone recent changes of level,
and if any of them have been more closely united within the period of
existing species than they are now, we may expect to find indications of
such changes in community of species between islands now widely
separated; while those islands which have long remained isolated would
have had time to acquire peculiar forms by a slow and natural process of
modification.
An examination of the relations of the species of the adjacent islands,
will thus enable us to correct opinions formed from a mere consideration
of their relative positions. For example, looking at a map of the
archipelago, it is almost impossible to avoid the idea that Java and
Sumatra have been recently united; their present proximity is so great,
and they have such an obvious resemblance in their volcanic structure.
Yet there can be little doubt that this opinion is erroneous, and that
Sumatra has had a more recent and more intimate connexion with Borneo
than it has had with Java. This is strikingly shown by the mammals of
these islands--very few of the species of Java and Sumatra being
identical, while a considerable number are common to Sumatra and Borneo.
The birds show a somewhat similar relationship; and we shall find that
the distribution of the Papilionidae tells exactly the same tale. Thus:--
Sumatra has 21 species }
Borneo " 30 " } 20 sp. common to both islands;
Sumatra " 21 " }
Java " 28 " } 11 sp. common to both islands;
Borneo " 30 " }
Java " 28 " } 20 sp. common to both islands;
showing that both Sumatra and Java have a much closer relationship to
Borneo than they have to each other--a most singular and interesting
result, when we consider the wide separation of Borneo from them both,
and its very different structure. The evidence furnished by a single
group of insects would have had but little weight on a point of such
magnitude if standing alone; but coming as it does to confirm deductions
drawn from whole classes of the higher animals, it must be admitted to
have considerable value.
We may determine in a similar manner the relations of the different
Papuan Islands to New Guinea. Of thirteen species of Papilionidae
obtained in the Aru Islands, six were also found in New Guinea, and
seven not. Of nine species obtained at Waigiou, six were New Guinea, and
three not. The five species found at Mysol were all New Guinea species.
Mysol, therefore, has closer relations to New Guinea than the other
islands; and this is corroborated by the distribution of the birds, of
which I will only now give one instance. The Paradise Bird found in
Mysol is the common New Guinea species, while the Aru Islands and
Waigiou have each a species peculiar to themselves.
The large island of Borneo, which contains more species of Papilionidae
than any other in the archipelago, has nevertheless only three peculiar
to itself; and it is quite possible, and even probable, that one of
these may be found in Sumatra or Java. The last-named island has also
three species peculiar to it; Sumatra has not one, and the peninsula of
Malacca only two. The identity of species is even greater than in birds
or in most other groups of insects, and points very strongly to a recent
connexion of the whole with each other and the continent.
_Remarkable Peculiarities of the Island of Celebes._
If we now pass to the next island (Celebes), separated from those last
mentioned by a strait not wider than that which divides them from each
other, we have a striking contrast; for with a total number of species
less than either Borneo or Java, no fewer than eighteen are absolutely
restricted to it. Further east, the large islands of Ceram and New
Guinea have only three species peculiar to each, and Timor has five. We
shall have to look, not to single islands, but to whole groups, in order
to obtain an amount of individuality comparable with that of Celebes.
For example, the extensive group comprising the large islands of Java,
Borneo, and Sumatra, with the peninsula of Malacca, possessing
altogether 48 species, has about 24, or just half, peculiar to it; the
numerous group of the Philippines possess 22 species, of which 17 are
peculiar; the seven chief islands of the Moluccas have 27, of which 12
are peculiar; and the whole of the Papuan Islands, with an equal number
of species, have 17 peculiar. Comparable with the most isolated of these
groups is Celebes, with its 24 species, of which the large proportion of
18 are peculiar. We see, therefore, that the opinion I have elsewhere
expressed, of the high degree of isolation and the remarkable
distinctive features of this interesting island, is fully borne out by
the examination of this conspicuous family of insects. A single
straggling island with a few small satellites, it is zoologically of
equal importance with extensive groups of islands many times as large
as itself; and standing in the very centre of the archipelago,
surrounded on every side with islets connecting it with the larger
groups, and which seem to afford the greatest facilities for the
migration and intercommunication of their respective productions, it yet
stands out conspicuous with a character of its own in every department
of nature, and presents peculiarities which are, I believe, without a
parallel in any similar locality on the globe.
Briefly to summarize these peculiarities, Celebes possesses three genera
of mammals (out of the very small number which inhabit it) which are of
singular and isolated forms, viz., Cynopithecus, a tailless Ape allied
to the Baboons; Anoa, a straight-horned Antelope of obscure affinities,
but quite unlike anything else in the whole archipelago or in India: and
Babirusa, an altogether abnormal wild Pig. With a rather limited bird
population, Celebes has an immense preponderance of species confined to
it, and has also six remarkable genera (Meropogon, Ceycopsis,
Streptocitta, Enodes, Scissirostrum, and Megacephalon) entirely
restricted to its narrow limits, as well as two others (Prioniturus and
Basilornis) which only range to a single island beyond it.