CHAPTER XXV

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 isPygolampis 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.

INSECTS THAT CARRY LAMPSThe 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 andeven 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 theEncyclopædia 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 speciesLuciola 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 thefemale 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 arésumé. 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 broughtfrom 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 piecesto 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 isbrilliant 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 palmEuterpe 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, bytheir 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 thecucujo, 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 thePyrophorusgive a stronger light than others. The above passage, by the way, if it be from theConquest 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 thePyrophorusit must be the great lantern-fly—also of South America—provided only that the great lantern-flyisluminous. 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 theMygale—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 manyflames 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: “TheFulgora lanternariaof 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 ofFulgora 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 hisGuide to Insects, that “Mr. Caleb Cooke, of Salem, who resided several years in Zanzibar, Africa, told me that the lantern-flyis 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 theFulgoridæhas 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 ofHotinus spinolaseated 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 thisFulgoridjumped, 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 theFulgorid—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 ofHotinus; 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.

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