"COMING OUT"--ICHNEUMONS--THE BUTTERFLY PERFECTED--ITS
WINGS--LEPIDOPTERA--MEANING OF THE WORD--MICROSCOPIC VIEW--NEW
BEAUTIES--MAGNIFIED "DUST"--THE HEAD AND ITS ORGANS--THE TONGUE--THE
EYES--THE ANTENNÆ--THEIR USES--INSECT CLAIRVOYANCE--AN UNKNOWN
SENSE--FORMS OF ANTENNÆ--THE LEGS.
We now arrive at the last stage, the consummation of all this strange
series of transformations; for veritable transformations they are to all
intents and purposes; though some learned naturalists have discovered--or
imagined so--that the butterfly, in all its parts, really lies hid under
the caterpillar's skin, and can be distinguished under microscopical
dissection; and that, therefore, the so-called transformations are merely
the throwing off of the various envelopes or husks, as they become in turn
superfluous, as a mountebank strips off garment after garment, till lastly
the sparkling harlequin is discovered to view; or, in more exact language,
they consider these changes in the light rather of successive developments
and emancipations of the various organs than as their actual
transformations. Still, it seems to me, the difference is chiefly one of
terms. The real wondrous fact remains undiminished and {17} unexplained;
that a creeping wormlike creature, in process of time, is changed into a
glorious winged being, differing from the former in form, habits, food, and
every essential particular, as widely as any two creatures can well differ,
as widely as a serpent from a bird, for instance.
As the imprisoned butterfly approaches maturity, a change is observable in
the exterior of the chrysalis, the skin becomes dry and brittle, usually
darkens in colour, and if the enclosed butterfly be a strongly marked one,
the pattern of its wings shows through, often quite distinctly.
When the fulness of time arrives, the creature breaks through its thin
casings, which divide in several places, and the freed insect crawls up
into some convenient spot to dry itself, and allow the wings to expand.
All the organs are at first moist and tender, but on exposure to the air
soon acquire strength and firmness.
At the moment of emergence, the wings are very miniature affairs, sometimes
hardly one-twentieth of their full size when expanded; but so rapid is
their increase in volume, that they may actually be seen to grow, as the
fluids from the body are pumped into the nervures that support the
wing-membrane, and keep it extended.
In the more strongly marked, or richly coloured species, it is a
wonderfully beautiful sight to watch this expansion of the wings, and to
see the various features {18} of their painted devices growing under the
eye and developing gradually into their true proportions.
Generally within an hour the development is complete, and the wings, having
gained their full expanse and consistency by drying in the sun, are ready
for flight, and the glad creature wings his way to the fields of air, and
enters on that life of sunshine and hilarity which is associated with the
very name of "_Butterfly_."
But not every chrysalis arrives at this happy consummation of its
existence. Supposing that you have reared and watched a caterpillar to
apparently healthy maturity, that it has duly become a chrysalis, and you
are awaiting its appearance in butterfly splendour--peeping into your box
some morning to see if the bright expected one is "out," be not surprised
if in its stead you find the box tenanted by a swarm of little black
flies--an impish-looking crew. Whence came all these? Why they and the
empty chrysalis shell are all that remains of your cherished prize; so look
no more for the fair sunny butterfly, devoured ere born by that
ill-favoured troop of darklings who have just now issued from the lifeless
shell.
The truth is, that long since, perhaps in early larva-hood, the creature's
fate was sealed; a deadly enemy to his race is ever on the alert, winging
about in the shape of a small black fly, in search of an exposed and
defenceless caterpillar. Having selected her victim, she pierces his body
with a sharp cutting instrument she is armed with, and in the wound
deposits an egg; the {19} caterpillar winces a little at this treatment,
but seems to attach little importance to it. Meanwhile his enemy repeats
her thrusts till some thirty or forty eggs, germs of the destroyers, are
safely lodged in his body, and his doom is certain beyond hope. The eggs
quickly hatch into grubs, who begin to gnaw away at the unhappy creature's
flesh, thus reducing him gradually, but by a profound instinct keeping
clear of all the vital organs, as if knowing full well that the creature
must keep on feeding and digesting too, or their own supply would speedily
fail; as usurers, while draining a client, keep up his credit with the
world as long as they can.
Weaker grows the caterpillar as the gnawing worms within grow stronger and
nearer maturity. Sometimes he dies a caterpillar, sometimes he has strength
left to take the chrysalis shape, but out of this he _never_ comes a
butterfly--the consuming grubs now finish vitals and all, turn to pupæ in
his empty skin, and come out soon, black flies like their parent.
But, supposing that it has escaped this great danger, we now see the
creature in its completest form, as the
IMAGO, OR PERFECT BUTTERFLY.
The first term, _Imago_, is a Latin one, merely signifying an image, or
distinct unveiled form; as distinguished from the previous _larva_, or
masked state, and the _pupa_, or swathed and enveloped state. The word
_imago_ then, in works on entomology, always means the {20} perfect and
last stage of insect life, and is applied to all insects with wings--for it
must be borne in mind that no insect is ever winged till it reaches the
last stage of its existence.
If the progressive development of these lovely beings is so marvellous, no
less so is their structure when perfected, and of this some general
description must now be attempted.
In contemplating a butterfly, one feels that the mind is first engaged by
that ample spread, and exquisite painting of the wings that form the
creature's glory; let therefore these remarkable organs have our first
attention.
Wherein do these wings chiefly differ from all other insect wings?
Certainly in being covered thickly with a variously coloured powdery
material, easily removed by handling. This apparent dust is composed, in
reality, of a vast number of regularly and beautifully formed
_scales_--feathers they are sometimes called, but they are more comparable
to fish scales than to any other kind of natural covering. The general term
_Lepidoptera_, applied to _all_ butterflies and moths, is derived from
these _scaly-wings_; _Lepis_[2] being the Greek for a _scale_, and _ptera_
meaning _wings_ in the same language.
The use of a tolerably powerful pocket lens will afford _some_ insight into
the exquisite mode of painting
{21} employed in these matchless pieces of decoration; but the possessor of
a regular microscope may, by applying it to some of our commonest
butterflies, open for himself a world of beauty, and feast his eyes on a
combination of refined sculpture with splendour of colouring; now melting
in softest harmony, then relieved by boldest contrast--a spectacle, the
first sight of which seldom fails to call forth expressions of wonderment
and warm delight; and, truly, little to be envied is the mind untouched by
such utter beauty as here displayed.
As an example of the method by which this admirable effect is produced, let
us take a small portion of the wing of the Peacock, a very beautiful,
though an abundant species, and one admirably adapted for microscopic
examination, and to illustrate the subject, from the great variety of rich
tints brought together in a small space, the part selected being the
eye-like spot at the outer corner of each upper wing. Even to the naked eye
this appears as a very splendidly coloured object, yet but little of its
exquisite mechanism can be discovered by the unassisted organ. Something
more is brought out by a moderately strong lens: we then see the colours
disposed in rows, reminding us of the surface of Brussels carpet, or of
certain kinds of tapestry work.
Now let us place the wing on the stage of a good microscope, with the root
of the wing pointing towards the light (that is the best position for it);
we shall then first perceive that the whole surface is covered, or, so to
{22} speak, tiled over with distinct, sharply cut _scales_, arranged as in
fig. 16, Plate II., with the outer or free edges of one row overlapping the
roots of the next. These roots being all planted towards the base of the
wing, if we place that end next the light (as above directed), the free
edges of the scales throw a strong shadow on the next row, which brings out
the imbricated effect most strikingly.
Beginning our observations at the outer edge of the wing, we first notice a
delicate fringe of scales or plumes, more elongated and pointed than the
surface scales, and of a quiet brown colour. This tint is continued inwards
for a short space, gradually lightening, when (as we shift the field of
view towards the centre of the wing) the colour of the scales suddenly
changes to an intense black; then a little further, and the black ground is
all spangled with glittering sapphires, then strewed deep with amethyst
round a heap of whitest pearls. Golden topaz--(jewels only will furnish apt
terms of comparison for these insect gems)--golden topaz ends the bright
many-coloured crescent, and in the centre is enclosed a spot of profoundest
black, gradating into a rich unnameable red, whose velvet depth and
softness contrast deliciously with the adjacent flashing lustre; then comes
another field of velvet black, then more gold, and so on till the gorgeous
picture is complete.
Subject a piece of finest human painting to the scrutiny of a strong
magnifying glass, and where is the beauty thereof? Far from being
magnified, it will have wholly vanished: its cleverest touches turned to
coarse, repulsive daubs and stains.
[Illustration: IV.]
{23}
Now, bring the microscope's most searching powers to bear upon the painting
of an insect's wing, and we find only pictures within pictures as the
powers increase; the very pigments used turn out to be jewels, not rough
uncut stones, but cut and graven gems, bedded in softest velvet.
If by gentle rubbing with the finger-tip the scales be removed from both
sides of the wing (for each side is scale-covered, though generally with a
very different pattern), there remains a transparent membrane like that of
a bee's or fly's wing, tight stretched between stiff branching veins, but
bearing no vestige of its late gay painting, thus showing that the whole of
the colouring resides in the scales, the places occupied by the roots of
the latter being marked by rows of dots.
Hitherto we have been looking at these scales as the component parts of a
picture, like the _tesseræ_ of mosaic work; but they are no less
interesting as individual objects, when viewed microscopically. To do this,
delicately rub off a little of the dust or scales with the finger; then
take a slip of glass, and pressing the finger with the adhering dust upon
it, the latter will come off and remain on the glass, which is then to be
placed under the microscope. These scales may be treated either as opaque
or transparent objects, and in both conditions display exceeding beauty,
some of these single atoms showing, by aid of the microscope, as {24} much
complexity of structure as the whole wing does to the unassisted vision.
A few of the highly varied forms they present are shown on Plate II. Figs.
23 to 38 are selected from among the commoner forms, as seen by a
comparatively low power. The small stalk-like appendage is the part by
which the scale is affixed to the wing: it may be called the root. Figs.
17, 18, 19, 20, 21, show some very remarkable forms, which are, so far as
has been ascertained, peculiar to butterflies of the _male_ sex, though the
use or reason of this masculine badge, only visible to highly magnifying
optics, is neither known nor probably to be known at present; but
singularly beautiful and curious they are to look at. The little balls at
the end of threads are the root portion, and fit into cup-like sockets,
placed here and there among the ordinary scales. The surface of these
scales is beautifully ribbed and cross-ribbed, and at the upper end is a
plume-like tuft of delicate filaments. The curious scale aptly called, from
its shape, the Battledore scale, and shown at fig. 22, also belongs to the
male of various butterflies, especially those pretty little ones known as
the "Blues." Its surface is most curiously ornamented with rows of
bead-like prominences.
Probably one would imagine that in such wee specks as are these scales, one
single layer of substance would suffice for their whole thickness (if we
can talk of _thick_ness, with objects almost immeasurable in their
_thin_ness). But such is not the case, for when scales have {25} been
injured by rubbing we now and then find a part with the sculptured surfaces
torn off on each side, showing a plain central layer, so that at least
three layers--two ornamented and one plain--go to form a filmy body, only a
small fraction of the thickness of paper.
But there are other portions of a butterfly to claim our interest besides
its wondrous wings.
On the creature's head are grouped together some most beautiful and
important organs. The most peculiar of these is the long spiral "sucker,"
which extracts the honied food from the blossoms to which its wings so
gracefully waft it. This organ is shown, slightly magnified, at fig. 8,
Plate II., and a most delicate piece of animal mechanism it is. Any human
workman would, to a certainty, be not only puzzled, but thoroughly beaten,
in an attempt to construct a tube little thicker than a horse-hair, yet
composed throughout its length of two distinct pieces, capable of being
separated at pleasure, and then joined again so as to form an air-tight
tube. This redoubtable problem, however, is solved in the construction of
this curious little instrument that every butterfly carries.
The junction of the two grooved surfaces that form the tube is effected by
the same contrivance that reunites the web of a feather when it has been
pulled apart. We all know how completely it is made whole again, and on
examining by what means this result is brought about, we find that it is by
the interlacing of a {26} number of small fibres or hairs, just as, on a
larger scale, a pair of brushes adhere when pressed face to face; and so in
the butterfly's sucker, the two edges that join to form the tube are
closely set with minute bristles that, when brought together, interlock so
closely as to make an air-tight surface.
Fig. 9, Plate II., is a transverse section taken near the base of the
sucker, the small opening at the top being the food passage, those at the
side the air-tubes that supply air for respiration and perhaps assist in
suction.
The tube is probably made with separable parts in order that if its
interior should become at any time clogged by grosser particles drawn up
with the flower nectar, it may be opened and cleansed by the insect;
otherwise, the tube once rendered impassable, the insect would speedily
starve, as this narrow channel is the only inlet for the creature's
nourishment--its only mouth, in fact, for no butterfly possesses jaws to
bite with, or can take any but the liquid food pumped up by suction through
this pipe.
At the end of the proboscis--or, as it is called scientifically, the
Haustellum[3]--there are visible in some butterflies a number of small
projections, of the form shown at fig. 10, Plate II., which is a highly
magnified figure of the end of the Red Admiral's proboscis. These
appendages are generally supposed to be organs of taste, {27} and to aid in
the discrimination of food when the pipe is unrolled and thrust down deep
into the nectary of a flower.
The _compound eye_ of a butterfly, wonderful as its structure is, does not
greatly differ from that of many other insects, being like them composed of
an immense number of little lenses set together to form a hemisphere large
in comparison with the insect's head. A portion of one of these eyes forms
a pretty and interesting object for the microscope, presenting a honey-comb
appearance, the hexagonal lines that mark the division of the lenses being
most beautifully geometrical and regular in their arrangement. More than
seventeen hundred of these lenses have been counted in a single eye, and
each of these is considered to possess the qualities of a complete and
independent eye. If this be true, the butterfly may be said to be endowed
with at least thirty-four thousand eyes!
There exist also, as in other insects, _two simple_ eyes, placed on the top
of the head, but so buried in down and scales as to be neither visible, nor
useful for vision as far as we can perceive; probably the creature finds
that his allowance of thirty-four thousand windows to his soul lets in as
much light as he requires.
Every one looking at a butterfly must have remarked its long horns, called
_antennæ_,[4] which project from above the eyes, like jointed threads,
thickening--in some {28} species gradually, in others suddenly--into a club
or knob at the extremity; a peculiarity which, it will be remembered, was
pointed out at the commencement, as a prominent mark of distinction between
butterflies and moths.
Very graceful appendages are these waving _antennæ_, and evidently of high
importance to their owner; but still, their exact office or function is
unknown, notwithstanding that many guesses and experiments have been made
with a view of settling that question.
Investigators have perhaps erred, by assuming at the outset that these
antennæ _must_ be organs of some sense that we ourselves possess; whereas,
I think that there is much evidence to show that insects are gifted with a
certain subtle sense, for which we have no name, and of which we can have
as little real idea, as we could have had of the faculty of sight, had all
the world been born blind.
For example; if you breed from the chrysalis a female Kentish Glory Moth,
and then immediately take her--in a closed box, mind--out into her native
woods, within a short space of time an actual crowd of male "Glories" come
and fasten upon, or hover over, the prison-house of the coveted maiden.
Without this magic attraction, you might walk in these same woods for a
whole day and not see a single specimen, the Kentish Glory being generally
reputed a very rare moth; while as many as some 120 males have been thus
decoyed to their capture in a few hours, by the charms of a couple of lady
"Glories," shut up in a box.
[Illustration: V.]
{29}
Now, which of our five senses, I would ask--even if developed into
extraordinary acuteness in the insect--would account for such an exhibition
of clairvoyance as this?
May not, then, this undiscovered sense, whatever may be its nature, reside
in the antennæ? for it is a remarkable fact, that the very moths, such as
the Eggers, the Emperor, the Kentish Glory, &c., which display the
above-mentioned phenomenon most signally, have the _antennæ in the males_
amplified with numerous spreading branches, so as to present an unusually
large sensitive surface. This seems to point to some connexion between
those organs and the faculty of discovering the presence, and even the
condition, of one of their own race, with more, perhaps, than a mile of
distance, and the sides of a wooden box, intervening between themselves and
their object.
Whilst writing this, the current number of the "Entomologist's Weekly
Intelligencer" has arrived, and I there read that Dr. Clemmens, an American
naturalist, has been lately experimenting on the antennæ of some large
American moths, for the purpose of gaining some information as to their
function. The article, though very interesting, is too long for quotation
here; but it appears that with the moths in question, a deprivation of the
whole, or even part of the antennæ, interferes with, or entirely
annihilates the power {30} of flight, so that the creature when thus shorn,
but not otherwise injured, if thrown into the air seems to have no idea of
using his wings properly, but with a purposeless flutter tumbles headlong
to the earth. Still this merely goes to prove that the antennæ are the
instruments of some important sense, one of whose uses is to guide the
creature's flight; but as many wingless insects have large antennæ, this
evidently is not their only function.
The antennæ are also often styled the "feelers;" but with our present
incomplete knowledge of their nature, the former term is preferable, as it
does not attempt to define their use as the word "feelers" does.
Considerable variety of form exists in the clubbed tip of the antennæ in
various butterflies, as will be seen by reference to Plate II., where three
of the most distinct forms are shown considerably magnified. Fig. 12 is the
upper part of the antenna of the High-brown Fritillary (_Argynnis Adippe_),
the end suddenly swelling into a distinct knob. Fig. 13 is that of the
Swallow-tail Butterfly (_Papilio Machaon_), the enlargement here being more
gradual; and fig. 14 is that of the Large Skipper Butterfly (_Pamphila
Sylvanus_), distinguished by the curved point that surmounts the club.
These differences in the forms of the antennæ are found to be excellent
aids in the classification of butterflies, and I shall therefore have
occasion to refer to them more minutely in describing the insects in
detail.
The stems of these organs are found to be tubular, {31} and at the point of
junction with the head the base is spread out (as shown at fig. 15),
forming what engineers call a "flange," to afford sufficient support for
the long column above.
The _legs_ are the last portions of the butterfly framework that require
especial notice, on account of a peculiar variation they are subject to in
different family groups.
It may be laid down as an axiom, that _all true insects have six legs_, in
one shape or another; and butterflies, being insects, are obedient to the
same universal rule, and duly grow their half-dozen legs; but in certain
tribes the front pair, for no apparent reason, are so short and imperfect
as to be totally useless for walking purposes, though they may possibly be
used as hands for polishing up the proboscis, &c. So the butterfly in this
case _appears_, to a hasty observer, to have only _four_ legs.
This peculiarity is a constant feature in several natural groups of
butterflies, and therefore, in conjunction with other marks, such as the
veining of the wings and the shape of the antennæ, its presence or absence
is a most useful mark of distinction, in classifying or searching out the
name and systematic place of a butterfly.
* * * * *
{32}