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or Scale-winged, par excellence, including the gay tribes
of Butterflies and Moths, presents us with many exceed-
ingly interesting varieties in these singular coverings. The
study of these might be almost as wide as the immensity
of species; I can only show you a few examples.

Here are specimens from the pretty little white Five-
plume Moth (Pterophorus), so common in meadows in sum-
mer. The general shape of the scales from the body and
wings is that of a willow- leaf, some singly pointed, but
more cut at the tip into two, three, or four notches.
Those from the legs are longer and slenderer in propor-
tion; and among the others from the wings, there are
some which take the form of hairs, which send forth one
or more branches from one side, that form a very acute
angle with the main stem. The scales proper are all
marked with longitudinal lines, very minute and close,
but they mostly bear a central band, and sometimes a
marginal one on each side, of spots set in sinuous lines
like the bands on a mackerel's back; these are probably
composed of pigment-granules.


These from the pretty Si-x-spot Burnet Hawkmoth are
nearly opaque, especially those from the red parts of the
wings, which have a rich ruddy glow by transmitted light.
They are narrow in shape, tapering gradually forward from
the foot- stalk, and terminate mostly in two blunt points.
The ribs are coarse for the size of the scales, and the
depressed spaces are marked with irregular pigment-

The hairs with which the bodies of Moths are invested
are essentially of the same character as the scales which
clothe their wings. Here are examples from the glowing
sides of the abdomen of that richly colored insect, the
Cream- spot Tiger-moth (Arctia villica). You see they
are simple scales, drawn out to an inordinate length and
great tenuity; each has its quill-like
foot- stalk, and we may trace on some
of them the ribs and transverse dotting,
while here we see all intermediate stages
between the slenderest hair and the
broadly ovate, bluntly - pointed scales
from the wings.

You are familiar of course with the
brilliant little Blue Butterfly (Polyom-
matus Alexis), which dances and glitters
in the sunshine on waste places in June.
Among the scales of ordinary form which
clothe the lovely little wings will occur
one here and there of a different shape BATTLEDOOR SCALE OF PO-


from the rest. Here you may see one;

it is much smaller than the average; the foot-stalk is very

long, and the shape of the entire scale is that of a battle-

door c The ribs are rather few and coarse, and they have


this peculiarity, that each rib swells at intervals into
rounded dilatations, each of which has a minute black
point in its centre. In some of these battledoor scales
there is, near the lower part of the expansion, a crescent
of minute pigment- grains.

The silvery gray surface of the front wings of a common
moth, known as the Buff -tip (Pygcera bucephala), is com-
posed of scales of unusual magnitude, and of a remark-
able form, their shape being that of an expanded fan, and
being quite distinguishable by the unassisted eye. The
ribs are very fine and numerous, and there are diverging
lines of pigment- grains running through the scale.

Those of the Emperor Moth (Saturnia pavonia- minor)
are likewise triangular in outline, and are remarkable for
being deeply notched at the end; so deeply as to leave
projecting points (from two to five) as long as, or even
longer than the integral portions of the scale.

In some species we find scales the tips of which are
furnished with a curious sort of fringe. This slide pre-
sents several such in the midst of many of a more ordinary
shape and appearance. The scales in question are straight,
and parallel- sided, rather narrow, with the basal end
rounded, and the terminal extremity tapered abruptly to
a point; it is on each slope of this point that the fringe
is arranged. The surface does not appear to be elevated
in ribs, but smooth; while the whole interior, except a
crescent around the foot- stalk, is filled with pigment- grains,
imparting a mottled appearance. It is remarkable that all
the scales of this form have the foot-stalk turned in under
the expanse. The example which we are considering is
from the white portion of the wing of Pieris Glaucippe,
a fine butterfly from China; but a similar structure is found



in our own Garden Whites and Meadow Browns (Piericfa
and Satyridce).

Scales taken from the brilliant changeable blue-green
patch in the hind-wing of Papilio Paris, a fine Indian
butterfly, have an interesting appearance. They are sim-
ply pear-shaped in outline, with few longitudinal ribs set
far apart, and numerous strongly- marked corrugations run-
ning across between them. That these are really eleva-
tions of the surface is well seen in some scales, even with
transmitted light, and a high power; for the slopes of the
wrinkles that face the light display the lustrous emerald
reflection proper to the wing, while the
transmitted color of the whole scale is a
rich transparent red.

The dimensions of the scales do not
bear any certain proportion to the size of
the insect which is clothed with them; those
from the broad wings of the noble Satur-
nia Atlas, for example, eight or nine inches
in expanse, being exceeded in size by some
from those of our little native Muslin Moth,
an inch wide.

YOU will Say that what I am about to FRINGED SCALE or

show you is a lovely object; but for its
right display I must use a low magnifying power not
higher than a hundred diameters with the Lieberkuhn
to reflect the light of the mirror full upon the sur-
face. It is a small fragment cut from the wing of Pa-
pilio Paris, showing several rows of the scales in their
natural arrangement. The gemmeous radiance of the
glittering green scales on the black ones, by which they
are environed, glares out with a splendid effect; and, what



is more interesting, you can trace the manner in which
they are set those of each row slightly overlapping the
bases of another row, like slates on a roof and also the
mode in which they are inserted. The clear horn-colored
membrane of the wing is seen raised in shallow transverse
steps (if I may use such a term) so that if it were divided
longitudinally, the edge would appear cut into saw-like
teeth. Along the margins of these ridges are set minute
sockets, which are very distinctly seen, where the scales

have been displaced: in
these the tiny foot- stalks
of the scales are inserted.
The little Beetles which
we are familiar with un-
der the name of Weevils,
characterized by their
long slender snouts, at the
end of which they carry
curiously folding anten-
nae, and which constitute the family Curculionidm, are in
many cases clothed with scales, to which they owe their
colors and patterns. Several of our native species display a
green or silvery lustre, which under the microscope is seen
to be produced by oval scales. But these are eclipsed by
the splendor of many tropical species; especially that well-
known one from South America, which is called the Dia-
mond Beetle, and scientifically Entimus imperialis, from
its unparalleled magnificence.

A piece of one of the wing-cases of this beetle is
gummed to the slide now upon the stage. We look at it
by reflected light with a magnifying power of 130 diam-
eters. We see a black ground, on which are strewn a pro-



fusion of what look like precious stones blazing in the
most gorgeous lustre. Topazes, sapphires, amethysts, ru-
bies, emeralds seem here sown broadcast; and yet not
wholly without regularity, for there are broad bands of
the deep black surface, where there are no gems, and,
though at considerable diversity of angle, they do all point
with more or less precision in one direction, viz., that of
the bands.

These gems are flat transparent scales, very regularly
oval in form, for one end is rather more pointed than the
other; there is no appearance of a foot-stalk, and by what
means they adhere, I know not; they are evidently at-
tached in some manner by the smaller extremity to the
velvety black surface of the wing-case. The gorgeous ool-
ors seem dependent in some measure on the reflection of
light from their polished surface, and to vary according
to the angle at which it is reflected. Green, yellow, and
orange hues predominate; crimson, violet, and blue are
rare, except upon the long and narrow scales that border
the suture of the wing-cases, where these colors are the
chief reflected. Yet there appears to be some positive
color in their substance; for in these latter scales, which
projecting beyond the edge of the wing-case can be exam-
ined as transparent objects, and that with a high power,
the transmitted light is richly colored with the same tints
as the same scales displayed under the Lieberkuhn.

We may derive pleasant instruction from continuing
our observations on a few other wings of insects. If you
have ever thought on the subject, you have probably taken
for granted that the various sounds produced by insects
are voices uttered by their mouths. But it is not so. No
insect has anything approaching to a voice. Yocal sounds


are produced by the emission of air from the lungs vari-
ously modified by the organs of the mouth. But no insect
breathes through its mouth; no air is expelled thence in a
single species; it is a biting, or piercing, or sucking organ;
an" organ for the taking of food, or an organ for offence or
defence; but never an organ of sound.

The wings are in most cases the immediate causes of
insect sounds. On this subject you will read with pleas-
ure some very interesting remarks by the learned Mr.
Kir by, inquiring, "by what means these sounds are pro-

"Ordinarily, except perhaps in the case of the gnat,
they seem perfectly independent of the will of the animal;
and, in almost every instance, the sole instruments that
cause the noise of flying insects are their wings, or some
parts near to them, which, by their friction against the
trunk, occasion a vibration as the fingers upon the strings
of a guitar yielding a sound more or less acute in propor-
tion to the rapidity of their flight, the action of the air
perhaps upon these organs giving it some modifications.
Whether, in the beetles that fly with noise, the elytra [or
wing sheaths] contribute more or less to produce it, seems
not to have been clearly ascertained; yet since they fly
with force as well as velocity, the action of the air may
cause some motion in them, enough to occasion friction.
With respect to Diptera, Latreille contends that the noise
of flies on the wing cannot be the result of friction, be-
cause their wings are then expanded; but though to us
flies seem to sail through the air without moving these
organs, yet they are doubtless all the while in motion,
though too rapid for the eye to perceive it. When the
aphidivorous flies are hovering, the vertical play of their


wings, though very rapid, is easily seen; but when they
fly off it is no longer visible. Kepeated experiments have
been tried to ascertain the cause of sound in this tribe,
but it should seem with different results. De Geer, whose
observations were made upon one of the flies just men-
tioned, appears to have proved that, in the insect he ex-
amined, the sounds were produced by the friction of the
root or base of the wings against the sides of the cavity
in which they are inserted. To be convinced of this, he
affirms, the observer has nothing to do but to hold each
wing with the finger and thumb, and, stretching them out,
taking care not to hurt the animal, in opposite directions,
thus to prevent their motion and immediately all sound
will cease. For further satisfaction he made the following
experiment. He first cut off the wings of one of these
flies very near the base ; but finding that it still continued
to buzz as before, he thought that the winglets and pois-
ers, which he remarked were in a constant vibration, might
occasion the sound. Upon this, cutting both off, he exam-
ined the mutilated fly with a microscope, and found that
the remaining fragments of the wings were in constant mo-
tion all the time that the buzzing continued; but that by
pulling them up by the roots all sound ceased. Shelver's
experiments go to prove, with respect to the insects that
he examined, that the winglets are more particularly con-
cerned with the buzzing. Upon cutting off the wings of
a fly but he does not state that he pulled them up by the
roots he found the sound continued. He next cut off
the poisers the buzzing went on. This experiment was re-
peated eighteen times with the same result. Lastly, when
he took off the winglets, either wholly or partially, the
buzzing ceased. This, however, if correct, can only be a


cause of this noise in the insects that have winglets. Num-
bers have them not. He next, therefore, cut oft' the pois-
ers of a crane-fly (Tipula crocata), and found that it buzzed
when it moved the wing. He cut off half the latter, yet
still the sound continued; but when he had cut off the
whole of these organs the sound entirely ceased." '

There is a pretty little beetle (Clytus), not uncommon
in summer in gardens, remarkable for the brilliant gam-
boge-yellow lines across its dark wing-cases, which makes
a curious squeaking sound when you take it in your hand.
You think it is crying; but if you carefully examine it
with a lens while the noise is uttered, you will perceive
that the cause is the grating of the thorax against the front
part of the two wing-cases. Several other beetles produce
similar sounds when alarmed, by rubbing the other end of
the wing-sheaths with the tip of the abdomen. Many of
those genera which feed on ordure and carrion do this.

But the noisiest of all insects are those of the classes
Orthopiera and Homoptera, the Crickets and Grasshoppers,
and the Treehoppers. And these shall bring us back to
our microscope, to which we shall return with the more
zest, after this little interval of repose for our strained


Listen! we hear coming up the kitchen- stairs the strid-
ulous chirping of the House- cricket (Acheta domesticd).

"The cricket chirrups on the hearth."

The cook shall catch us one for investigation. "Please,
sir, here's the crickets: here's half a dozen on 'em. I
don't like 'em, I don't; nasty noisy varmint!" Thank

1 "Introd. to Entom.," Lett. xxiv.


you, cook; we'll try and turn them to some useful pur-
pose to-day, at least.

Now, you see, each of the upper wings or wing-cases
has a clear space near the centre, of a triangular form,
crossed by one or two slender nervures. This space has
received the name of the tympanum or drum. It is bounded
externally by a broad dark nervure, which with a low power
we see is scored with three or four longitudinal furrows, of
course separated by as many horny ridges. In front of the
clear drum, and forming a curved base to the triangle,
there passes across a horny ridge, tapering outward, which
is roughened throughout its length by close- set teeth ex-
actly like a file. When the insect chooses to be musical
it partially opens and closes its wing-sheaths, causing the
two files to rub across each other; and this gives rise to
the peculiar ringing vibration, the intensity of which is
heightened by the tense "drum" acting as a sounding

So at least some say; but M. Groureau, who has pub-
lished some elaborate observations on the chirping of in-
sects, l asserts that the sound is chiefly owing to the action
of the "file" (which he calls the "bow") on the longitudi-
nally-ridged nervure, which he calls the " treble- string. "

We see in this individual, that is so obliging as to
produce what cook calls its "nasty noise" before us, that
he elevates the wing-sheaths so as to form an acute angle
with the body, and then rubs them together with a very
brisk horizontal motion; but which of the nervures it is
that actually produces the sounds it would require a very
careful and elaborate series of experimental researches to
determine. It has been asserted that the legs play a part
1 "Ann. Soc. Ent. de France."


in the music by being rubbed against the bows; this, how-
ever, seems improbable from their relative position.

In the Southern United States I have had opportuni-
ties of seeing and of hearing a very noisy performer of
the Grryllus tribe, called the Katydid (Pterophylla concava),
which sings through the night in the foliage of the trees.
The sounds, reiterated on every side, resemble a score or
two of quarrelsome people with shrill voices, divided into
pairs, the individuals of each pair squabbling with each
other: "I didl" "You didn't!" "I did!" "You didn't!"
the objurgation maintained with the most amusing perti-
nacity, and without a moment's intermission. Here the
wing-sheaths, which are large and as it were inflated, are
certainly the organs of sound. A portion of each is turned,
at right angles to the remainder, over the back, so that the
one partly overlaps the other. The musical organ consists
of a hard glassy ridge in front, behind which is a trans-
parent me'mbrane, which appears tightly stretched over a
semicircular rim, like the parchment of a drum, answering
in structure and in function to the part so compared in the

This Gryllus I found would crink freely, when held
in my fingers, provided I held it by the head or thorax,
so as not to interfere with the freedom of the wing-cases;
though these needed only to be partially opened, the bases
being merely slightly separated without affecting the gen-
eral contiguity. The two glassy ridges were rubbed across
each other, making the sharp crink. Ordinarily this was
done thrice, three distinct but rapid crossings making the
sound represented by the word "Katydid"; but occasion-
ally the insect gave but a single impulse, uttering as it
were but one syllable of the word.


The Locusts and Grasshoppers, however, do, it appears,
make use of their hind legs in producing their crink. If
you look at this Grasshopper's leg, you will see that the
thigh is marked with a number of transverse overlapping
angular plates, and that the shank carries a series of short
horny points along each side. The insect when it crinks
brings the shank up to its thigh, and rubs both to and fro
against the wing-sheaths, doing this by turns with the right
and left legs, which causes the regular breaks in the sound.
The drum, on which this rubbing vibrates, has been de-
scribed by the anatomist, De Geer: "On each side of the
first segment of the abdomen," says he, "immediately
above the origin of the posterior thighs, there is a con-
siderable and deep aperture of rather an oval form, which
is partly closed by an irregular flat plate or operculum of
a hard substance, but covered by a wrinkled flexible mem-
brane. The opening left by this operculum is semilunar,
and at the bottom of the cavity is a white pellicle of con-
siderable tension, and shining like a little mirror. On
that side of the aperture which is toward the head there
is a little oval hole, into which the point of a pin may be
introduced without resistance. When the pellicle is re-
moved, a large cavity appears. In my opinion this aper-
ture, cavity, and above all the membrane in tension, con-
tribute much to produce and augment the sound emitted
by the grasshopper. ' ' l

In this case we may without hesitation conclude that
the friction of the thigh- plates and shank- points on the
rough edges of the wing-cases produces the musical vibra-
tion of the tense membrane, as rubbing a wet glass with
the finger will yield a loud musical note.

1 De Geer, iii. 471.


The most elaborate contrivance for the production of
sounds among the Insect races, however, is found among
the Cicadae, celebrated in classical poetry as the very im-
personations of song and eloquence. I regret I cannot
show you this apparatus; for though we have a British
species lately discovered in the New Forest it is very
rare. Should you travel, however, either in the old or
new world, you will have abundant opportunities of using
your microscope to verify the following description by
our prince of entomologists, Mr. Kirby.

"If you look at the under side of the body of a male,
the first thing that will strike you is a pair of large plates
of an irregular form in some semioval, in others tri-
angular, in others again a segment of a circle of greater
or less diameter covering part of the belly, and fixed to
the trunk between the abdomen and the hind legs. These
are the drum- covers or opercula, from beneath which the
sound issues. At the base of the posterior legs, just above
each operculum, there is a small pointed triangular proc-
ess, the object of which, as Reaumur supposes, is to pre-
vent them from being too much elevated. When an
operculum is removed, beneath it you will find on the
exterior side a hollow cavity, with a mouth somewhat
linear, which seems to open into the interior of the ab-
domen: next to this, on the inner side, is another large
cavity of an irregular shape, the bottom of which is di-
vided into three portions; of these the posterior is lined
obliquely with a beautiful membrane, which is very tense
in some species semiopaque, and in others transparent
and reflects all the colors of the rainbow. This mirror
is not the real organ of sound, but is supposed to modu-
late it. The middle portion is occupied by a plate of a


horny substance, placed horizontally, and forming the
bottom of the cavity. On its inner side this plate termi-
nates in a carina or elevated ridge, common to both drums.
Between the plate and the after-breast (postpectus) another
membrane, folded transversely, fills the oblique, oblong,
or semilunar cavity. In some species I have seen this
membrane in tension; probably the insect can stretch or
relax it at its pleasure. But even all this apparatus is
insufficient to produce the sound of these animals; one still
more important and curious yet remains to be described.
This organ can only be discovered by dissection. A por-
tion of the first and second segments being removed from
that side of the back of the abdomen which answers to the
drums, two bundles of muscles meeting each other in an
acute angle, attached to a place opposite to the point of
the mucro of the first ventral segment of the abdomen, will
appear. In Eeaumur's specimens, these bundles of mus-
cles seem to have been cylindrical; but in one I dissected
(Cicada Capensis) they were tubiform, the end to which
the true drum is attached being dilated. These bundles
consist of a prodigious number of muscular fibres applied
to each other, but easily separable. While Eeaumur was
examining one of these, pulling it from its place with a
pin, he let it go again, and immediately, though the ani-
mal had been long dead, the usual sound was emitted.
On each side of the drum- cavities, when the opercula are
removed, another cavity of a lunulate shape, opening into
the interior of the abdomen, is observable. In this is the
true drum, the principal organ of sound, and its aperture
is to the Cicada what our larynx is to us. If these creat-
ures are unable themselves to modulate their sounds, here
are parts enough to do it for them; for the mirrors, the


membranes, and the central portions, with their cavities,
all assist in it. In the cavity last described, if you remove
the lateral part of the first dorsal segment of the abdomen,
you will discover a semiopaque and nearly semicircular
concavo-convex membrane with transverse folds; this is
the drum. Each bundle of muscles, before mentioned, is
terminated by a tendinous plate nearly circular, from which
issues several little tendons that, forming a thread, pass
through an aperture in the horny piece that supports the
drum and are attached to its under or concave surface.
Thus the bundle of muscles, being alternately and briskly
relaxed and contracted, will by its play draw in and let

Online LibraryPhilip Henry GosseEvenings at the microscope (Volume 1) → online text (page 7 of 32)