CHAPTER VIII.

FIRE-FLIES.

Some years ago an American gentleman, visiting in one of the large cities of South America, was invited to a masquerade ball at one of the finest private residences in the city. The ball-room was the garden,--a veritable fairy-land abounding in plants of the most novel and beautiful description,--and upon the grass had been laid an extended platform for the dancers. It was moonlight when the festivities began, and no artificial lights were used; yet at various intervals among the flowers soft gleams appeared, apparently for ornament. Among the first comers was a tall gentleman dressed in a style of several centuries ago, a most picturesque costume; but what particularly attracted the attention of the American were the decorations of this gentleman and his companion. Around the broad-brimmed hat he wore a band of what appeared, from a distance, to be gems, that flashed like diamonds, presenting a magnificent appearance. The lady’s costume was still more remarkable, being fairly ablaze with these brilliant scintillations. As the evening wore on, he was presented to these maskers, when he found that the light proceeded from innumerable luminous insects which had been secured by delicate wires, and fastened upon the hat and the lady’s dress.

About the garden, hundreds of the insects were confined in delicate glass globes, which without emitting much light, added to the charm and novelty of the surroundings.

In Vera Cruz these beetles are so commonly used as toilet ornaments that they form an important article of trade; and the natives make a business of catching them, and in a way that would seem to show that the lights of insects are their means of recognition. The fire-fly hunters provide themselves with long sticks, upon the end of which is fastened a burning coal. This waved in the air attracts the light-givers, and they are entrapped in a net. They are then placed in a box covered with a wire netting, bathed twice a day in tepid water, and at night fed with sugar-cane.

The insects utilized in this curious manner are fire-flies,--distinguished from the lightning-bugs by the steady glare they produce. And that the lights of these Elaters, as they are scientifically called, is intense, and of practical value in other ways, we may realize from the statement of Professor Jaeger, who says, “I feel particularly grateful to these little insects, because, during my excursions in St. Domingo, they were frequently the means of saving my life. Often has dark night surrounded me in the midst of a desert forest, or on the mountains, when the little animals were my only guide; and by their welcome light I have discovered a path for my horse, which has led me safely on my journey.” If a number are confined in a glass, they emit sufficient light to read by.

It is in the genus _Pyrophorus_ that we find the most remarkable light-givers; the different species being found principally in tropical America. In Plate XI. _Pyrophorus noctilucus_, a form common in the West Indies and Brazil, is shown. It ranges from 1.50 to 1.75 inches in length; is a black or rusty-brown color; and, if observed during the daylight, two conspicuous oval spots of a yellowish white hue are seen on each side of the prothorax. These are the lanterns of the Elaters, and in the dark glow with a brilliancy far exceeding that of the lightning-bugs. These lights shine from above, while between the part known as the metathorax and the first abdominal segment gleams another, or lower light, even more brilliant than the other: so the _Pyrophorus_, turn which way it will in its flight, emits a flash of light. The light appears to be dependent upon the will, as when feeding or asleep it is not seen; attaining its greatest brilliancy during activity and flight. The color of the light, as seen by the author, is a rich green; but the eggs emit a light of a bluish tint, according to Dubois. This naturalist has made some extremely interesting experiments with this beetle. The eggs which he dried retained their luminosity for a week, the light re-appearing when they were placed in water. He ground the luminous organs in a mortar, after having dried them in vacuum, and then mixed them in boiled water; the latter immediately becoming luminous. Dr. Dubois concludes that the light of the _Pyrophorus_ is intended as an illuminator for itself alone. To prove this, he covered one of the upper lights with wax, and the animal moved in a curve; when both spots were covered, the beetle soon stopped, and then moved in an uncertain manner, carefully feeling the ground with its _antennæ_. The spectrum of the light was extremely beautiful, being continuous, without dark or brilliant rays; and, what appears most remarkable, the composition of the light was found to change with its intensity. As to the exact cause of the light, how it is produced, the secret yet rests with Nature.

Dr. Kidder thus refers to the brilliancy of one of these wondrous light-givers: “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 now distinctly see.”

The insect was the _Pyrophorus noctilucus_; a longish click-beetle of a dull blackish-brown color, and covered over with a short, slight-brown pubescence. When walking or at rest, the chief light that it emits proceeds from the two yellow tubercles on the thorax, so conspicuous in dead specimens; but, when flying, another luminous spot is discernible on the hinder part of the thorax, and this is continued to the under side of the insect.

Ovideo says that the Indians travel in the night with these insects fixed to their hands and feet; and that they spin, weave, paint, dance, etc., by their light. In Prescott’s “Conquest of Mexico,” we are told that in 1520, when the Spaniards visited that country, “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 it. These wandering flies, seen in the darkness of the night, were converted, by the excited imaginations of the besieged, into an army of matchlocks.”

[Illustration:

PLATE XII.

THE LANTERN FLY.

(_Fulgora lanternaria._)

According to Madame MERIAN, Marquis SPINOLA, and others.]

At the time of the discovery of Hispaniola, Peter Martyr assures us that the natives, in their night journeyings through the woods, were in the habit of fastening a number of these light-givers to their feet to light the way. On this occurrence Southey founds the incident mentioned in “Madoc” where Coatel guides Madoc through the cave:--

“She beckoned, and descended, and drew out From underneath her vest a cage,--or net It rather might be called, so fine the twigs Which knit it,--where, confined, two fire-flies gave their lustre.”