Sights of the forest—A butterfly bridge—Bird-winged
butterflies—“What’s in a name?”—Scientific
sensibility—Resemblance _v._ mimicry—A convenient wrong
word—Beauty in nature—Nuptial display—Strange
counter-theory—_Lucus a non lucendo_—Reasoning by
contraries—True in Topsy-turvydom—Butterfly courtship—Form
and colour—A curious suggestion—Powers of defective
eyesight.
THOUGH the principle of protective resemblance, as explained in the last
chapter, will account for the colours and markings of those butterflies
which imitate the _Heliconidæ_, it does not explain how the _Heliconidæ_
themselves came to be as they are; for in nature every mark and line and
shade has a meaning, and has come into existence by virtue of some law
or another. Beauty itself, independently of any _arrière pensée_, as we
may call it—remembering those flower-resembling spiders—requires to be
explained.
Nor are the _Heliconidæ_ themselves, though gaudily dressed showy
butterflies, anything like so beautiful as many others; for instance, as
the _Morphos_, those giants of their kind, who sweep like stars through
the tropical forests on wings whose whole broad surface is blue, but a
blue that flashes like a drawn sword and has a hundred glints and
gleamings of ever-varying light. High-fliers they are for the most part,
keeping to the tops of the trees, but every morning, and always at the
same time, they make a descent into the glades and alleys of the forest,
where for a little they flap lazily backwards and forwards, now in
eclipse, now flashing forth into sunlight, as though to flaunt their
beauties in the face of the lower world. Such openings in the primeval
forest are often made by the fall of great trees—for even where the axe
is not there is death in the midst of life—and as these majestic insects
sail high above them in a world of air and light, their shadows fall
upon the place beneath, and trace their course along the ground. When
the sun’s rays strike into them, such clearings become the gathering
grounds of various butterflies. Besides the great _Morphos_, the
flashing of whose wings in the sunlight can be seen sometimes a quarter
of a mile away,[112] various species of _Heliconeas_—the one we have
just been reading about—whose black wings are in some species spotted
with scarlet, in others with white or blue, waltz about the bushes or
undergrowth, “dancing in the chequered shade”; fritillaries somewhat
like our own, but of larger size and more effective colouring, fly
higher up, about the tree-trunks, whilst over the ground itself,
carpeted as it often is with flowers fallen from the leafy world above,
and scenting the air, ghost-like butterflies, whose clear, transparent
wings are without any colouring matter, ceaselessly hover and flit.
Wherever there is a river, many-coloured armies, bivouacked amidst its
various shoals and reefs, sit sucking water through, the moist particles
of the sand, whilst others, in even greater numbers, pass and repass
from one bank to another, making, however wide the waterway, an aerial
fluttering bridge. Other butterflies, also denizens of the great
Brazilian or Central American forests, have broad white wings, shot with
a satiny lustre, whilst those of yet another are like glass, with one
opaque spot of violet and blue, in the midst of each of them. In flight
this spot is the only part that can be seen, and it looks, Bates tells
us, “like the wandering petal of a flower.”[113] There are
swallow-tailed butterflies, too, whose livery of deep, soft green, and
deeper velvet black, set off with roseate hues, is amongst the richest
of all—“rich, not gaudy,” so at least I should term it, for I have seen
it, putting flowers to shame, on the lower slopes of the Himalayas. Here
these butterflies—double the size of our _Machaon_, and of another
shape, with racquet-rather than swallow-tails, flew on the open
hillside, courting the sun, but in Brazil they keep to the forest
depths, where, like Una, they “make a sunshine in the shady place.”
The butterflies of South America are almost rivalled—quite they cannot
be—by those of the Malay Archipelago. Here we have the great Bird-winged
Butterfly, discovered by Dr. Wallace, who calls it “elegant,” and
bestows upon it a name (_Ornithoptera Brookeana_) which is not quite
that.[114] However, “What’s in a name? That which we call a
_Brookeana_,” etc.—we must reverse the proposition. There is no
describing such a creature—at least, not convincingly. Suffice it to say
that its wings “almost resemble those of a sphinx moth in shape,” and
are deep, velvety black, but lit up with a band of green feather-like
markings, so brilliant and lovely that they reminded its discoverer “of
the wing-coverts of the Mexican trogon laid upon velvet”[114]—and that
for anyone who has seen a trogon, even stuffed and dried, is to say
enough. Besides this adornment the great _Brookeana_ has “a broad
neck-collar of vivid crimson and a few delicate white touches on the
outer margins of the hind wings.”[114] Another _Ornithoptera_ without
the _Brookeana_ is “the largest, the most perfect, and the most
beautiful of butterflies.” The two last, however, are matter of opinion,
and I should think myself that a _Morpho_ with its azure wings,
sometimes seven inches across, and flashing a quarter of a mile away,
would run—or fly—it hard. Then there is a yet more gorgeous species of
“Bird-winged Butterfly,” with wings equalling or even exceeding the
_Morpho’s_ in expanse, whose ample surface is divided between flame-like
orange and a black so deep, rich, and velvety that it seems to glow—“the
pride of the Eastern tropics, one of the most gorgeously coloured
butterflies in the world.”[115]
This was the butterfly that gave Dr. Wallace a headache, “so great was
the excitement produced by what will appear to most people a very
inadequate cause.”[115] Surely not; for the cause here alluded to was
not the insect’s beauty—which had been seen before, free and
untrammelled, without any such ill-consequence—but its capture and
anticipated transference to the cyanide bottle. It was not mere æsthetic
emotion, therefore, that produced the headache, but scientific
enthusiasm, of which no man need feel ashamed. It is easy for us on such
occasions to mistake our feelings, but the clue to them, I think, is
this, that however beautiful a creature may be, and however appreciative
we may think ourselves of such beauty, yet if we resolve, in the true
interests of science, to take that creature’s life, then the scientific
spirit must be far stronger in us than mere admiration of its beauty.
This test I would apply to another account which Dr. Wallace gives us of
the capture of “one of the most magnificent insects that the world
contains.” “I trembled,” he says, “with excitement as I saw it coming
majestically towards me, and could hardly believe I had really succeeded
in my stroke till I had taken it out of the net and was gazing, lost in
admiration, at the velvet black and brilliant green of its wings—seven
inches across—its golden body, and crimson breast. It is true I had seen
similar insects in cabinets at home, but it is quite another thing to
capture such oneself—to feel it struggling between one’s fingers, and to
gaze upon its fresh and living beauty, a bright gem shining out amid the
silent gloom of a dark and tangled forest. The village of Dobbo held
that evening at least one contented man.”[116] When we consider that the
“fresh and living beauty” was caught for the very sake of being made
dead and mouldy, and that the “bright gem” which would otherwise have
continued to flash in the forest was about to become one of those very
same specimens that had been looked at with such an inferior degree of
interest, we must admit, I think, that the higher of two passions was
predominant here, and that the author, in dwelling only upon the other
and lower one—mere delight of the eye—has done himself less than
justice.
Mr. Bates, without headaches, has given us some very pleasing pictures
of butterfly-life in the tropics, and in doing so he has instinctively,
as it were, kept the killing and capturing in the background. “The
number and variety of gaily-tinted butterflies,” he tells us, “sporting
about in this grove on sunny days, were so great that the bright moving
flakes of colour gave quite a character to the physiognomy of the place.
It was impossible to walk far without disturbing flocks of them from the
damp sand at the edge of the water, where they congregate to imbibe the
moisture. They were of almost all colours, sizes, and shapes. I noticed
here altogether eighty species belonging to twenty-two different genera.
It is a singular fact that, with very few exceptions, all the
individuals of these various species thus sporting in sunny places were
of the male sex; their partners, which are much more soberly dressed and
immensely less numerous than the males, being confined to the shades of
the woods. Every afternoon, as the sun was getting low, I used to notice
these gaudy, sunshine-loving swains trooping off to the forest, where I
suppose they would find their sweethearts and wives.”[117] What a
delightful scene! Here, “next to the very common sulphur-yellow and
orange-coloured kinds, the most abundant were about a dozen species of
_Eunica_, of large size, conspicuous from their liveries of glossy dark
blue and purple. A superbly adorned creature, the _Callithea Markii_,
having wings of a thick texture, coloured sapphire blue and orange, was
only an occasional visitor. On certain days, when the weather was very
calm, two small gilded green species literally swarmed on the sands,
their glittering wings lying wide open on the flat surface.”[117]
Such, then, are the colours of butterflies, and, as may be imagined,
comparatively few of these gorgeous liveries have been acquired through
the principle of protective resemblance—using the term in its widest
sense, to include those cases where one species becomes, as it were, the
double or wraith of another. Mimicry is the word which, by a ludicrous
process of false reasoning, naturalists have convinced themselves it is
right to apply to this particular kind of resemblance, and no other one;
though why a butterfly should _mimic_ another butterfly and only
_resemble_ a leaf, “_quien sabe?_” as the Spaniards say. The principal
reason adduced for this misuse of language, viz. that the wrong word is
more convenient than any right one, providing us with the useful series,
_mimic_, _mimicry_, _mimetic_, _mimicker_, _mimicked_, _mimicking_,
obviously applies to the one case as well as the other, and if it is an
advantage to be absurd in one way, surely it is a double one to be
absurd in two. On these grounds I would suggest to naturalists that,
having broken down the proper and natural confinements of the word in
question, they should rather extend its use than limit it, to the extent
even of calling their children “mimetic forms,” should they happen to
resemble them, and thinking twice before punishing a son for merely
“mimicking” his father.
But, leaving this, how—to take the jargon as one finds it—are the
glorious colours of butterflies to be explained when they are due
neither to protective resemblance, which is not mimicry, though it very
much resembles it, nor to mimicry, which is distinct from protective
resemblance, though mimicking it exactly? Certainly neither of these
will do to account for uncopied hues and patterns, which are like
nothing in the world but their own loveliness, unless, indeed, it be the
rival glories of the most resplendent birds. Still less will aggressive
resemblance—though, as we see, it can make spiders look like
flowers—explain them. The great governing cause which produces such
effects as these, as well as most others in nature, is natural
selection; but we must look beyond natural selection even, if we wish to
understand all the beauty that we see in the animal world, and
especially the higher developments of it.
Darwin, as we know, was the great demonstrator—though not the first
conceiver—of the law of natural selection,[118] and on this he might
have cried “_Nunc dimittis_” and retired, so to speak, leaving someone
else to find out the other law; but instead of that he went on and
demonstrated that too. This other law, the evidence for which is really
overwhelming, and has never been met by anything better than a conceited
over-estimation of human superiority, wrapped up in a cloud of wrong
reasoning, is that of sexual selection, which implies that, in the
choice of their mates, animals, like ourselves, are guided by some sort
of preference; and as this with them—again like ourselves—is usually
determined by the element of beauty, the most beautiful partners are
being constantly selected, and species in consequence become more and
more beautiful. This process, however, is usually confined to the males,
they being the eager wooers, whilst the females only wait to be courted,
and then shyly and modestly choose—such, at least, is the supposition.
This masculine beauty is often inherited by that sex only to which it is
so useful, but in other cases it is transmitted to the female also.
Thus, to take birds, where the results of the law of sexual selection
are on the whole most pronounced, we have, on the one hand, the
pheasants and birds of paradise, where the male alone is resplendent,
whilst in the trogons, parrots, and many other species the beauty is
common to both the sexes. As is well known, the males of various highly
ornate birds are accustomed to make the most extraordinary display of
their beauty before the females, making the most of the parts most
richly decorated, assuming just such attitudes as are required in order
to give these their full advantage, and, in fact, taking pains and
trouble in a high degree and of a very special and peculiar kind, which
must either be directed to an end which seems perfectly plain and
apparent, or else so much waste of time—due to no special cause and
without any particular meaning—an alternative which the opponents of
sexual selection do not in the least mind accepting.
To give one instance of what is called nuptial display in birds—for it
will serve to illustrate what Darwin supposes to take place with some
insects also, as well as forming a basis of comparison with what has
been more carefully observed in the case of spiders—Belt in his often
quoted work gives us the following pretty picture of humming-bird
courtship. Speaking of a beautiful blue, green, and white species
(_Florisuga mellivora_), he says: “I have seen the female sitting
quietly on a branch, and two males displaying their charms in front of
her. One would shoot up like a rocket, then suddenly expanding the
snow-white tail like an inverted parachute, slowly descend in front of
her, turning round gradually to show off both back and front. The effect
was heightened by the wings being invisible from a distance of a few
yards, both from their great velocity of movement and from not having
the metallic lustre of the rest of the body. The expanded white tail
covered more space than all the rest of the bird, and was evidently the
grand feature in the performance. Whilst one was descending, the other
would shoot up and come slowly down expanded. The entertainment would
end in a fight between the two performers; but whether the most
beautiful or the most pugnacious was the accepted suitor I know
not.”[119]
Here the display, as well as the intention, seems evident enough, and it
is not a whit more so than in hundreds of other cases collected by
Darwin during his lifetime, and which have been largely added to since
his death. As the hen is constantly present during these performances,
and as she has been known on various occasions to show a strong
partiality, or the reverse, to this or that male bird, we have here a
solid basis of observed fact on which to raise an hypothesis. On what
facts the counter one rests, as propounded by Dr. Wallace, viz. that
colour and antics are produced by superior vigour resident in the male,
it is less easy to see, unless, indeed, such as point in a quite
opposite direction may, on a sort of _lucus a non lucendo_ principle, be
held to support it. If this be conceded, then, indeed, we have a
plentiful crop, nor need we any longer feel sceptical because the eagle,
say—that bird of fierce energy—does not flash out like all the crown
jewels together as it descends on its prey, or because the swift, whose
vital force is, perhaps, even greater, leaves no train of jewelled light
to die all day, behind it, on the air. Nor need we wonder that the
trogons, though as resplendent as the swifts, swallows[120] and eagles
are dull-coloured, should be as lazy and sluggish as these are
energetic: nor that, whereas the females of some humming-birds are
sober-suited, those of others, though their vigour would seem to be in
no way superior, are as gem-like as their mates: or that the males as
well as the females of some wholly dull-coloured ones, and of many other
plain birds, seem bursting with vigour, and indulge in all sorts of
strange antics and dances: that a cock partridge, for instance, seems as
vigorous as a cock pheasant, and that bright colours and pugnacity are
dissociated in such tremendous fighters as the ruff, the coot, and the
blackcock. Multiply such instances by the score or the hundred—as can
easily be done—and if only the above-stated principle be granted, we get
more and more proof of the correctness of a theory to which facts, if
dealt with in the more usual way, would be almost instantly fatal. After
all, this would be a more satisfactory mode of procedure than that of
tolerating a travesty on the strength of a high reputation. There is
such a principle in nature as the _lucus a non lucendo_ one, so, as we
admit the word mimicry in a false sense—because it is convenient—why not
admit that? It would be not one whit less convenient—for the theory.
But, handling facts in another way, can we explain the beautiful colours
of butterflies as we explain the brilliant plumage of birds—by sexual
selection, that is to say? Of this there is not so much direct evidence
as could be wished, for butterfly courtship is a long affair, and, for
various reasons, is not so easy to watch under natural conditions, as in
the case of birds, though this, too, is often beset with difficulties.
We know, however, that the male is often much more beautiful than the
female, that he pirouettes around her, and that she remains often “icy
insensible”—in fact refuses him—which certainly implies a power of
choice. Rival males, too, will “whirl round each other with the greatest
rapidity, and appear to be incited by the greatest ferocity.”[121] That
butterflies, like bees, perceive and are attracted by colours is well
known, and it would be strange, indeed, if they were not alive to the
many very beautiful and complex patterns on their own wings, when these
cannot have been evolved through any principle of protection—since they
resemble or suggest nothing—when, in fact, if not beauty, it is
difficult to see the object aimed at. Yet the strange suggestion has
been made that, though butterflies see colours, they cannot see form,
that their sight is defective in some peculiar kind of way. But if form
is outline—and if not, what is it?—where is the distinction, seeing that
the beginning and leaving off of a colour or of two or more colours must
make an outline, and therefore a form? If we see the colours of a
pattern where the one ends and the other begins, we see that pattern,
and on the other hand, if we could not distinguish one colour from
another, or colour from something uncoloured—as, say, the air—we should
be blind to colour, as well as to form. Form can hardly be called a
thing of itself. It is rather the line of demarcation between two or
more things, so that, if each of these is clearly perceived, the form or
outline which their juxtaposition makes must be also perceived. Assuming
that butterflies see the beautiful arrangements of colour—eyes, spots,
bands, lines, etc.—in such a way as can alone account for their being
there to see—as well as we do, that is to say—then it is absurd to
imagine that they have no perception of form.
On what is this assertion based? Mr. Scudder relies on the following
facts: “Christy,” he tells us, “observed in Manitoba one of the
swallow-tails fluttering over the bushes, evidently in search of
flowers. As he watched it, it settled momentarily, and exactly as if it
had mistaken it for a yellow flower, on a twig of _Betula glandulosa_,
bearing withered leaves of a bright yellow colour.”[122] But might not
the association of ideas raised by a familiar colour in an insect’s mind
overpower for a moment its judgment? Might it not do so in the case of a
man also? And should we think a person very stupid who, for a moment,
mistaking a yellow leaf for a yellow flower, stretched out his hand to
pick it? Pooh! once again,[123] let us think of people who do foolish
things—kings, generals, cabinet ministers, servant-maids, etc.—not of
infallible persons. We should not be too severe—not “break a butterfly
on a wheel.”
Again—this is Mr. Scudder’s second instance: “Albert Müller records
seeing the blue Alexis of Europe fly towards a very small bit of pale
blue paper lying upon the grass, and stop within an inch or two of it,
as if to settle, doubtless mistaking it for another of its own
kind.”[124] Surely this is rather in favour of the butterfly’s sight
than otherwise, since it discovered its mistake and did not settle. Who,
too, can tell the precise moment at which the mistake was discovered,
since the piece of blue paper might have puzzled the butterfly—piqued
its curiosity to know what it was—even after it knew what it was not?
Thirdly, “Plateau has observed the small tortoise-shell butterfly fly
rapidly towards a cluster of artificial flowers.”[124] And who cannot be
taken in by artificial flowers? “Such examples as these,” says Mr.
Scudder, “seem to indicate that butterflies may perceive colour in mass,
but in no case indicate any further visual powers.”[124] To me they
indicate that butterflies can make mistakes. Mistakes rarely show one’s
perfections, but other indications of further visual powers are not
wanting. For instance, Mr. Scudder himself says: “One of my favourite
modes of showing this characteristic (inquisitiveness) to unbelieving
friends has been to toss my cap high in the air, when these butterflies
will often dart, dash at, and play around it as it begins again to
descend.”[124] How do they play around this moving object in the air if
it represents to them only “colour in mass,” and not a defined shape and
outline? Were it otherwise, they would fly right into it, and be carried
down with it sometimes on top of them. But if they see all parts of the
colour so that they can nicely avoid it, and sport about its periphery,
then they see the shape of the cap. Then, again, Mr. Scudder tells us:
“Many kinds are of a lively and even pugnacious disposition, and perch
themselves upon the tip of a twig, or on a stone, or some such outlook,
and dash at the first butterfly that passes, _especially if it be one of
their own species_;[125] then the two advance and retreat, forwards and
backwards, time and again, circle round each other with amazing
celerity, all the while, perchance, mounting skywards, until suddenly
they part, dash to the ground, and the now quiet pursuer again stations
himself on the very spot he quitted for the fray.”[126] How does he do
_that_ without accurate eyesight, with good defining power?—to which,
indeed, the whole performance bears witness. Elsewhere, too, this
pronounced characteristic of returning to the exact spot, left some
little time ago, is dwelt upon. To me it seems a complete upsettal of
the defective eyesight theory, or, since good eyesight could do no more,
what does such defectiveness matter?
The following description also, which Bates gives us, of butterfly-life
by the Amazons, does not suggest that any of these bright-day-lovers,
these children of the sun, need write an “_Apologia pro oculis suis_.”
“The fine showy _Heliconii_,” he says, “often assemble in small parties,
or by twos and threes, apparently to sport together or perform a kind of
dance” (my “dancing in the chequered shade,” therefore, was no inapt
quotation). “I believe the parties are composed chiefly of males. The
sport begins generally between a single pair. They advance, retire,
glide right and left in face of each other, wheel round to a
considerable distance, again approach, and so on; a third joins in, then
a fourth, or more. _They never touch_;[127] when too many are
congregated a general flutter takes place, and they all fly off, to fall
in again by pairs shortly afterwards.”[128] Lastly, Belt tells us this:
“Here a large spider built strong, yellow, silken webs joined one on to
the other, so as to make a complete curtain of web, in which were
entangled many large butterflies, generally forest species, caught when
flying across the clearing. I was at first surprised to find that the
kinds that frequent open places were not caught, although they abounded
on low white-flowered shrubs close to the webs; but on getting behind
them and trying to frighten them within the silken curtain, their
instinct taught them to avoid it, for, although startled, they threaded
their way through open spaces and between the webs with the greatest
ease.”[129] If a butterfly with defective eyesight can thread its way
between spiders’ webs, so as never to be caught, “with the greatest
ease,” “why, then, say an old man can do somewhat”—but it must be
without spectacles.
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Footnote 112:
Bates, The Naturalist on the River Amazon.
Footnote 113:
Ibid. (1864), p. 63.
Footnote 114:
Wallace, The Malay Archipelago, p. 29.
Footnote 115:
Ibid., pp. 257, 258.
Footnote 116:
Ibid., pp. 328, 329.
Footnote 117:
Bates, The Naturalist on the River Amazon (1864), p. 333.
Footnote 118:
In 1813 Dr. Wells, first amongst the moderns, conceived, or at least
formulated in writing, the idea of natural selection; but Aristotle,
as is usual in such cases, had anticipated him as well as Darwin,
Wallace, and one or two others, and that in a very unmistakable
sentence (see footnote on first page of the “Historical Sketch” in
_The Origin of Species_). It would seem, however, that no one of these
conceptions was influenced by any previous one. Of sexual selection
Darwin seems to have been the discoverer as well as, in the opinion of
many, the demonstrator.
Footnote 119:
Belt, The Naturalist in Nicaragua, pp. 108-12.
Footnote 120:
Swallows have the highest temperature known amongst birds, viz. 111¼.
Footnote 121:
C. Collingwood, Rambles of a Naturalist in the China Seas, p. 183.
Footnote 122:
Scudder, Frail Children of the Air.
Footnote 123:
See pp. 179-181.
Footnote 124:
Scudder, Frail Children of the Air.
Footnote 125:
My own italics.
Footnote 126:
Scudder, Frail Children of the Air.
Footnote 127:
My own italics.
Footnote 128:
“Contributions to an Insect Fauna of the Amazon Valley,” in _Trans.
Linn. Soc._, vol. xxiii, p. 495.
Footnote 129:
Belt, The Naturalist in Nicaragua, pp. 108-12.
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