One remark—Phosphorescent insects—Glow-worms and
fire-flies—Fiery courtship—A beetle with three
lamps—Travelling by beetle-light—The great lantern-fly
controversy—Is it luminous?—Madame Merian’s
statement—Contradictory evidence—A Chinese edict—Suggested
use of the “lantern”—Confirmation required—Luminous
centipedes.
NO marine insect—this is the remark—is phosphorescent—that is to say, as
far as I know, which is a very saving clause indeed. This seems curious,
because, as everyone knows, other sea-dwelling creatures are, producing
most wonderful and beautiful effects, and, moreover, the luminous
property is active in many terrestrial insects. Of these the glow-worm
is a familiar and, though, perhaps, the humblest, a very beautiful
example. At any rate, there are insects of the glow-worm family whose
fires are far less “ineffectual,” or, to speak more truly, far outglow
those of our own species. What, for instance, can be more gorgeous than
the green or orange lights—for they differ in colour according to the
sexes—with which the nights and the rich vegetation of the West Indies
are brilliantly, yet softly, lit up? Nothing, surely, if it be not the
name of the creature producing such splendour, which is _Pygolampis
xanthophotis_[146]—not one syllable less.
Whether it is the male or the female that gives out the green or the
orange light, I do not know, nor in my opinion do various monographists
in various encyclopædias and text-books, though they make no such
avowal, but content themselves with not saying. However, it is not a
matter of importance except to the insect producing it, in whose breast
the one or the other colour arouses very different sensations—rivalry or
love. For there is no doubt now that these lovely illuminations, as well
as those of our own glow-worm and of every other light-bearing creature,
have relation to the needs and wants of their producers, to whose
æsthetic sense, and not to ours, they are intended to appeal. That they
appeal also to our own is a mere irrelevant side-issue, not considered,
so to speak, by the force under whose pressure these beauties were
called forth, and not of the smallest consequence. It was not always
thought so, and were the pride of man reachable by such considerations
it might humiliate us to reflect that displays, which in real beauty
immeasurably surpass our clumsy illuminations and fireworks, are made
nightly, not for our eyes, but for those of a beetle.
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[Illustration: INSECTS THAT CARRY LAMPS
The glow-worms in this picture are rather larger than life. The male
insects have wings; it is the females chiefly, if not solely, that emit
the soft, beautiful light.]
Gilbert White, however, in the eighteenth century, exclaims amidst some
very pleasing verses:
“For see, the glow-worm lights her amorous fire!”[148]
on which one of his editors of the nineteenth remarks: “This is still
the generally received notion, but the fact is that both sexes of the
glow-worm are phosphorescent, not only in the perfect insect, but also
in the larva and even pupa state.”[147] But this does not affect White’s
statement, which is the simple fact, as well as “the generally received
notion,” and, moreover, though our own male glow-worm is phosphorescent,
it is not so brilliantly so as the female. Indeed, in the ninth edition
of the _Encyclopædia Britannica_—which is later than this editorial
note—it is stated not to be so at all, so that even if White believed
this—which is not very clear—he has been supported by learned authority
for a very long time.
In other species the male is the more brilliant, or the sexes do not
differ greatly in this respect, each one lighting its “amorous fire” in
the degree that nature allows it to—as no doubt our own male does too.
Of this fact, which, in the light of Darwinism, might have been boldly
assumed, there is no longer any doubt after Professor Emery’s
interesting observations[149] on the Italian species _Luciola Italica_.
These were made in the meadows around Bologna, where, having caught some
females, the Professor imprisoned them in glass tubes and laid them down
amidst the grass. In this situation, though smell as an attractive agent
was excluded, males would come flashing to the glass, and, on the other
hand, as soon as the lamp of any of these became visible, the female
would kindle her own, if it had previously been unlighted. Arrived on
the spot, the male would dash madly about the unapproachable female, who
continued to light her lamp at him till another, and then others,
arrived, when it is to be supposed that her favours were distributed. In
the end there would sometimes be a dozen fiery rivals glowing and
flashing round the tube. But though the female shot out her attractive
beams with evident intent to please, it does not appear that she was the
seeker in the business, since we hear only of males flying to the
imprisoned females, and not of females pursuing these males. To such
modest merit, therefore, as a nice distinction between different ways of
attaining the same end may entitle her, the female glow-worm also is
entitled.
The light of the two sexes in the Italian glow-worm is described by
Professor Emery as being the same in colour and intensity, but differing
in some other respects. The flashes of the male, for instance, are more
quickly recurrent, whilst those of the female gleam out at longer
intervals, but last for a longer time. They are, also, more tremulous,
as well as more restricted, though what is meant by this last
expression, since the brightness is said to be equal, is not quite
apparent. Possibly it may imply that the light proceeds from a lesser
area of the body, but, if so, this should be clearly stated, even in a
_résumé_. I can find no reference to such a fact, if it be one, in the
text-books.
From the above it is evident that the glow-worm’s fires are anything but
“uneffectual” from the point of view of the insect, but Shakespeare was
no doubt thinking of something very different—their paling, namely,
before the light of dawn. According to Gilbert White, however, they
should have been out long ago—the glow-worm being too wise to afford
opportunities of comparison in this respect. Thus subtly does the
naturalist of Selborne impugn the accuracy of the Bard of Avon: “By
observing,” he says, “two glow-worms which were brought from the field
to the bank in the garden, it appeared to us that these little creatures
put out their lamps between eleven and twelve, and shine no more for the
rest of the night.”[149] The intention here, though cleverly disguised,
is not sufficiently so to escape detection. It was possibly seen through
by the late Charles and Mary Cowden Clarke, who in one of the million or
so notes to their edition of Shakespeare, say, without distinct
reference to the passage in question:—“_Uneffectual._ There is double
signification included in this word; it means the glow-worm’s light,
which shines without giving heat, and which no longer shows when morning
appears.”[150] Thus whilst not committing themselves to White’s opinion
they provide a safe refuge for their author, in case it should prove in
time to be correct; according to the sound principle contained in a
Russian proverb which says, “Had he known where he was going to fall, he
would have laid down straw.”
In tropical countries fire-flies take the place of glow-worms with us,
and though the light which these give out is not so soft and poetic as
the lovely green or golden green one of the latter, yet it is more
effectively beautiful, owing to the way in which it wanders through the
night, appearing and disappearing in successive brilliant flashes. For
here the beetle that carries the lamp is a flier, and flashes it about
at pleasure through the air, having the power, it would seem, either of
showing or concealing its light. The effect of a number of these points
of brilliancy, gleaming out, now here, now there, on the soft night air
of the tropics, is inexpressibly beautiful, as though, in a smaller
firmament, innumerable miniature stars had ceaseless birth and death.
Women, who like to emphasise their own beauty, or the want of it, by
placing themselves in juxtaposition with every lovely thing in nature,
and care not if a thousand deaths go to help one smile or glance, have
not forgotten the fire-flies. They put them in their hair, or wire them
onto their dresses, threading them together, sometimes, in long bands,
which they wind about their fair—or otherwise—persons; they do this,
more especially, when going out to parties, fancy-dress balls, or other
social entertainments. The advantages are obvious, for the homeliest
features may be thus lighted up, and the dullest woman become brilliant.
No wonder that in some South American cities—Vera Cruz for example—these
fire-fly beetles form quite an important article of trade, all for
toilette purposes.[151] The natives catch them by waving sticks with
burning coals tied to their ends through the air, by the light of which
they are attracted, and so come within reach of a long-handled butterfly
net. When caught, they are put into a box covered with a little netting
of wire, and there kept till wanted. They are fed upon sugar-cane, and
twice a day must be bathed in tepid water.[151]
What is done with the poor beetles after they have contributed to the
night’s amusement we are never told—whether those that have been all
wired together are unwired and let go, or pulled off in two or more
pieces to save trouble, as seems more likely. It is likelier still
perhaps, in the houses of the rich, that the whole thing is flung aside,
and the poor living lamps left to struggle till they die—unprovided with
sugar-cane. But such details are not thought worth mentioning. The
charming effect is the one thing dwelt upon, and charming it may very
well be, though to gain it through a mass of even insect discomfort is,
to my mind, a contemptible thing. Fancy fifty or a hundred
uncomfortable, writhing, struggling things on the dress that a lady is
dancing in, every one of which, if let go, would make a wandering star
in the air more really worth looking at than the whole ball-room
together! By substituting flowers for women, however, effects far more
beautiful are gained through less reprehensible means. The
fire-beetles—why should they be called flies?—are in this case confined
in small globes of delicate glass, set amidst clusters of flowers, or
flowering shrubs, and thus they softly illuminate the garden. Give them
some sugar-cane whilst the party is in progress, and let them go next
morning, and they will have had very little to complain of—a strange
experience for any lower creature that gets into the clutches of the
highest one.
The most wonderful of all the fire-beetles is the large one of near two
inches long—quite, or more, if we count the antennæ—that inhabits
Mexico, where in ancient times it was used as a lantern by the Aztecs in
their night-journeys, as it still is by their modern descendants. It is
wonderful, not by reason of its size merely, or, in any special degree,
of the light it emits—though this is brilliant in proportion to it—but
because it carries three separate lamps: two above, situated on either
side of the thorax, and one on the under side, just in front of the
abdomen. Thus, as it turns or varies in its flight, one flash of the
most intense brilliancy follows another, like the revolving light of a
lighthouse. The colour of the light is described as a rich
green—richest, however, or at least brightest, on the under
surface.[151] The beauty and dazzling effect of this upon a dark night
can be imagined, and is thus described by Dr. Kidder: “Before retracing
my steps I stood for a few moments looking down into the Cimmerian
blackness of the gulf before me; and while thus gazing a luminous mass
seemed to start from the very centre. I watched it as it floated up,
revealing in its slow flight the long leaves of the palm _Euterpe
edulis_, and the minuter foliage of other trees. It came directly
towards me, lighting up the gloom around with its three luminosities,
which I could distinctly see.”[151] There is something wonderfully
poetical in the thought of winged beings like this pursuing each other
through the night, by the light of these glorious flashes—the “light of
their own loveliness,” it may well be called, since it is, indeed, their
beauty. If seems curious and a waste that where there is the greatest
capacity of poetic imagination we should find the least, or almost the
least, realisation of it in habit and structure.
We know from Oviedo that the Mexican Indians, when they travelled at
night, were accustomed to fasten these great refulgent beetles on their
hands and feet, and thus pass flaming through the country. They danced,
too, by their light, and even wove or painted by it. Why, therefore,
could not lamps of great power, as well as beauty, be evolved from such
insects by bringing the selective agency of man to bear upon them? The
phosphorescent principle in living nature has not perhaps been made the
most of by us. Was more made of it by the Aztecs? and did they turn
their attention to the systematic rearing of these living lamps?—for,
from hearing so little about them one would not think that these insects
were so useful now, as, from the above account and what other
contemporary Spanish writers tell us, it would seem that they were, at
the time of this old and cruelly destroyed civilisation.
Holder, in his work on phosphorescent animals, either quotes or refers
to Prescott as saying that “when the Spaniards visited the country”—that
is, Mexico, “the air was filled with the _cucujo_, a species of large
beetle which emits an intense phosphoric light from its body strong
enough to enable one to read by. These wandering flies, seen in the
darkness of the night, were converted by the excited imagination of the
besieged into an army of matchlocks.” Surely, from such a foundation,
something as superior to it as are our cultivated fruits, or domestic
breeds, to the wild stocks from which they sprung, might in no long time
be produced, since it is not to be supposed but that some individuals of
the _Pyrophorus_ give a stronger light than others. The above passage,
by the way, if it be from the _Conquest of Mexico_, as one might suppose
it to be, is most carefully concealed in the index, which, however, it
might very well be, and yet exist, as I know from much teasing
experience. As to the matchlocks, would to Heaven the old Mexicans, as
well as the Peruvians, had had them, or, still better, 11-inch
Howitzers. I might then have something more to say about these wonderful
beetles. All I can add now is that the light appears to be used by the
insect as a guide to its own movements, since when the celebrated Dr.
Dubois covered one of the side ones with wax, this caused the individual
so treated to walk in a curve, and when “both spots were covered it soon
stopped, and then moved in an uncertain manner, carefully feeling the
ground with its antennæ.”[151] But I do not know if “both” here means
all three of the lamps, or only the two upper ones.
If there be any luminous insect that eclipses the _Pyrophorus_ it must
be the great lantern-fly—also of South America—provided only that the
great lantern-fly _is_ luminous. That is a most essential point, and it
does not appear yet to have been satisfactorily made out. The principal
evidence on the affirmative side is that of Madame Merian, who was right
about the _Mygale_—the great bird-killing spider—and who here speaks as
an actual eye-witness. Her account is as follows: “The Indians,” she
says, “once brought me, before I knew that they shone at night, a large
number of these lantern-flies, which I shut up in a large wooden box. In
the night they made such a noise that I awoke in a fright, and ordered a
light to be brought, not knowing from whence the noise proceeded. As
soon as we found that it came from the box we opened it, but were still
more alarmed, and let it fall to the ground in a fright at seeing a
flame of fire come out of it; and as many animals as came out, so many
flames of fire appeared. When we found this to be the case we recovered
from our fright, and again collected the insects, highly admiring their
splendid appearance.”[151]
Here, then, is a definite statement, from which all possibility of
mistake seems excluded, if, as I suppose is the case, there is no doubt
as to the specific identity of the insect which was the subject of it,
and which is thus described by Mr. Holder in the work already mentioned:
“The _Fulgora lanternaria_ of South America,” he tells us, “is nearly
three and a half inches long from tip of head to extremity of tail (i.e.
abdomen), and almost five and a half inches broad with its wings
expanded.” Truly a goodly insect, of right portly dimensions, and if it
be not really luminous—upon occasions, at any rate, for it certainly is
not so generally—it is so much the greater pity. But to continue: “The
body is of a lengthened oval shape, while the head is distinguished by a
singular prolongation, which sometimes equals the rest of the body in
size.” This is a most remarkable appendage, if it may be called so,
hollow and with a blown-up, inflated sort of look. It does, indeed, to
some extent resemble a Chinese lantern, and seems made to be lighted up.
The colour, too, suggests this, since it is striped longitudinally with
red and yellow, presenting quite a gala appearance. Accordingly, it is
said to be here that the luminous property of this strange insect
exists. This is its lantern, and, by reason of it, it has received its
name of lantern-fly.
And yet, since that night when Madame Merian had her interesting
experience, we meet with no one, apparently, who can unequivocally say
that he has seen the Great Lantern-Fly with its lantern alight. On the
other hand, we have some second-hand statements which have almost the
value of first, such as that of M. Westmael, who “assures us that a
friend of his observed the luminosity”;[151] whilst “John C. Branner,
PH.D., states that when in South America he was often informed that it
was luminous, but never could find anyone who had personally seen the
light.”[151] The curious thing is that there are other lantern-flies
belonging to other parts of the world, and in regard to them too we have
the same doubt and discrepancy, the same assurances and general belief,
the same categorical denials. Thus a distinguished authority on the
subject of phosphorescence— Dr. Phipson—in referring to the smaller
Chinese species, _Fulgora candelaria_—the candle-fly—says: “It is from
these appendages, the sides of which are transparent, that the
phosphoric light appears.” And again: “It is said also that the trunk of
a tree covered with numerous individuals of _Fulgora candelaria_, some
in movement, others in repose, presents a very grand spectacle,
impossible to describe, but which may be witnessed sometimes in
China.”[151] It would seem, too, that there exists a Chinese edict which
forbids young women to keep these candle-flies; and if this is not with
the idea of preventing their use as signals, or of checking vanity, it
is difficult to see what the object of such an enactment can be.
Lastly, we are told by Packard, in his _Guide to Insects_, that “Mr.
Caleb Cooke, of Salem, who resided several years in Zanzibar, Africa,
told me that the lantern-fly is said by the native to be luminous. They
state that the long snout lights up in the night, and in describing it
say its head is like a lamp (_keetchwa kand-tah_).”
All this evidence appears to me to point in one way, and one way only—I
mean, of course, in its entirety, since otherwise it points in two ways.
But even if it is possible that in one country alone an insect—well
known and conspicuous—can have got the reputation of being luminous
without really being so, at least occasionally, this can hardly have
come about in regard to the same, or some allied insect, in three or
four countries. Added to this we have Madame Merian’s direct evidence,
but, on the other hand, it is perfectly clear that these insects are not
always, or even generally, luminous. The conclusion, then, seems
irresistible that they occasionally are so, that, for some reason or
other, the phosphorescent principle is active in them only at certain
times or seasons. Why this should be so we do not know, but there is
nothing inconceivable in it; and some other animals—for instance,
centipedes—would seem to be luminous at some times and not at others.
The so-called lantern or snout being a very remarkable organ, for which
some use must be assumed, the likelihood of its sometimes becoming a
lamp would be increased considerably, if, so far as we knew, it
performed no other office. This was how the case stood till lately; but
in 1899 there was the Skeat Expedition for scientific purposes to the
Malay Archipelago, and on its return Mr. Nelson Annandale propounded a
theory in regard to the more ordinary use, at least, of the organ in
question, which was based on his own observation. His account is as
follows: “The curious anterior prolongation of the head in many genera
of the _Fulgoridæ_ has long puzzled entomologists. At Biserat, in Jalor,
I was fortunate enough to observe the real use of this peculiar
structural modification. On the morning of May 30th I noticed a specimen
of _Hotinus spinola_ seated on the trunk of a Durian tree in the
village, and incautiously attempted to catch it in my hand. The insect
remained almost still, merely drawing in its legs towards its body and
pressing the claws firmly against the bark, until I had almost touched
it. Then it lowered its head with very great rapidity, flew up into the
air without spreading its wings, and alighted on the roof of a house six
feet behind a tree, and considerably higher than its position on the
trunk had been. At the time I did not notice anything peculiar in the
way in which this _Fulgorid_ jumped, for there are many large species of
the same family which, without being provided with long noses, can leap
for a considerable distance by means of their legs only; but as I was
examining my specimen (a dead one) I was struck by an indentation or
crease that ran across the central region of the nose at right angles to
its main axis. Then I discovered that at this point, and at this point
only, it was flexible, and that if the tip of the nose and the dorsal
surface of the abdomen were pressed together between the finger and
thumb, and then suddenly released, the insect would not fall straight to
the ground, but would be propelled for some distance through the air
before doing so, just as would be the case if a piece of whalebone were
treated in like manner.”[152]
Mr. Annandale then goes on to show, or to suggest, that the
_Fulgorid_—as he calls it—by pressing its snout—or lantern—against the
tree-trunk, and at the same time pushing itself off from it with its
legs, “would fly into the air at a tangent,” and he continues: “I have
no doubt that this is substantially what occurs in the case of
_Hotinus_; but in the living insect the action is far too rapid for the
eye to discriminate its details, and dead specimens cannot be made to
leap in this way because it is impossible to force the legs to perform
their part of the action.”[152] Such, then, is the theory, but as other
members of the family jump in much the same way, to all appearance,
without any such apparatus, and since the bending of the head, at such a
moment, might be correlated with the movements requisite to produce such
a leap as this, it certainly wants confirmation.
Some of the finest displays of luminosity have been observed in
centipedes, which although not insects, may be counted such for the
purpose of this volume. Thus M. Audouin, noticing one night a light
proceeding from one of his chicory-fields, “ordered his man to turn up
the earth, when the scene that followed is described as truly
magnificent. The soil appeared as if it had been sprinkled with molten
gold, the display being intensified if the insects were trodden upon or
rubbed. In the latter case streaks of light appeared, as if a bit of
phosphorus had been placed upon the hands, the light being distinctly
visible for twenty seconds.”[153]
Mr. Brodhurst, again, referring to another species—_Geophilus
electricus_—about an inch and a half in length, and in the daytime
inconspicuous enough, says: “The light looked like moonlight, so bright
was it through the trees. It was a dark night, warm and sultry. Taking a
letter, I could read it. It resembled an electric light, and proceeded
from two centipedes and their trails. The light illuminated the entire
body of the animal, and seemed to increase its diameter three times. It
flashed along both sides of the creature in sections, there being about
six, from head to tail, between which the light played, moving, as it
were, perpetually in two streams. The trail extended one and a half feet
from each centipede over the grass and gravel walk, and it had the
appearance of illuminated mucus. On securing one of the creatures for
examination, I found on touching it the light was instantly
extinguished.”[153] The display is, therefore, voluntary, nor could Mr.
Brodhurst ever get his centipedes to shine in captivity.
-----
Footnote 146:
Chambers’s Encyclopædia.
Footnote 147:
White, Natural History of Selborne (stereotyped edition), p. 84.
Footnote 148:
Ibid., p. 353.
Footnote 149:
Bull. Soc. Entomolog. Ital., 1885-7.
Footnote 150:
Cassell’s Illustrated Shakespeare, “Hamlet,” Act i., Scene 5, Note
137.
Footnote 151:
C. F. Holder, Living Lights.
Footnote 152:
Proceedings of the Zoological Society for 1900.
Footnote 153:
C. F. Holder, Living Lights.
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