Firefly, the popular name of many serri-corn beetles, belonging to the families elate-ridoe and lampyridae, and to the old genera elater and lampyris of Linnaeus; the luminous species of the former belong to the new world, those of the latter to both hemispheres; these insects are also called fire beetles. The elaters have a firm and solid body, of an oval form; the middle portion of the sternum between the first pair of legs is prolonged into a short spine usually concealed in a cavity behind it; the antennas in the males are simply serrated. They are called spring beetles from the faculty possessed by them of throwing themselves upward with a spring by means of the spine; as they live on plants, when they drop to the ground they often fall upon the back, whose great convexity and the shortness of the legs prevent them from turning over; the spine having been unsheathed by bending the head and thorax backward, it is made to strike with such force against the sheath by the sudden straightening of the body, that it projects the insect into the air, and gives it the chance of coming down on the feet; if unsuccessful, other attempts are made until the object is attained.
Fireflies of this tribe are numerous in tropical America, including the West Indies. One of the largest and most brilliant is the night-shining elater, or lightning spring beetle, the cucujo of the West Indies (pyrophorm noctilu-cus, Linn.); this is more than an inch long, of a dark color, and gives a strong light from two oval tubercles on the dorsal surface of the thorax, and from the under surface of the segments of the body. Specimens are frequently brought alive to the United States, where they may be kept for some time if fed on sugar cane; the grub is said to be very injurious to the sugar cane by devouring the roots; one of these was once transported to Paris, and escaping into the streets, after assuming its perfect state, very much astonished the inhabitants of that city. This insect is common in summer, both in the lowlands and at moderate elevations; according to Mr. Gosse, the thoracic light is visible even in broad daylight; when undisturbed, these spots are dull white, but they gradually become bright when touched, the brilliancy beginning at the centre and extending until the whole tubercle shines with a rich yellowish green.
The light is so intense that it will cast a shadow of any object on the opposite wall in a dark room; the under side of the thorax seems as if it were red-hot, particularly beneath the tubercles; when left to itself, the insect becomes quiet, and the light fades to a mere speck. The insect when held in the hand shows only a green light, but when flying free it diffuses a rich ruddy glow from the ventral surface; it may show the green light at any time, but the red light only when flying; the former is seldom shown during flight, but in rare instances both tints are seen, producing an exceedingly beautiful effect. The thoracic light is subject to the will of the insect, but the abdominal is by some considered involuntary; the former is intermittent, but the latter seems to be a constant red glare, which will illuminate the ground for the space of a yard square. There are more than a dozen other luminous elaters mentioned by Hliger, found in South America, where they fly during dusk and at night, generally remaining quiet during the day.
These insects are used by the natives, confined under gauze, as ornaments for their head dresses and garments; they have been usefully employed by the Indians for the purposes of illumination in their dwellings and in their journeys; several, confined in a glass vessel, give light enough to read small print by. This is one of many instances in which an acquaintance with natural history has dissipated the fears of the superstitious; the deceitful light of supposed malignant spirits has become the beautiful radiation of an insect sporting amid its inoffensive companions. These insects may be kept for weeks, if fed on sugar cane, and placed in damp moss; their light is more powerful than that of the glowworm. The larvae of many elaters are also more or less luminous. In the adults both sexes are luminous. (See American Naturalist," vol. ii., 1869, pp. 420-423.)-The genus lampyris (Fab.) includes the fireflies of the United States and the glowworm of Europe; they are characterized by soft and flexible bodies, straight and depressed; there is no snout, and the head in the males is occupied almost entirely by the eyes, and is much concealed by the thorax; the antennae are short, with cylindrical and compressed articulations; the abdomen is serrated on the sides; the elytra are coriaceous, and the legs simple; the females have only rudiments of elytra at the base of the abdomen.
The glowworms of Europe, L. noctiuca, L. Italica, L. splendidula, and L. hemip-tera, will be described under Glowworm. In the United States there are many species, of which the L. scintillans (Say) and L. corusca (Linn.) are familiar examples. The latter is 4| lines long; the body is oblong pubescent, brownish black; a rose-colored arched streak, dilated and yellower anteriorly, joins the elevated thoracic disk; the elytra are obsoletely carinated, with numerous minute dots; it is found as far north as 54°. Both sexes are luminous, but the light is strongest in the female; the light streams from the ventral surface of the abdomen; even the larva) of many species, and also the eggs, are luminous. Like the elaters, they conceal themselves by day, and gly about in warm damp evenings; the males fly from plant to plant, while the female remains still, betraying herself to the other sex by her brighter light, of a bluish or greenish white tint. The luminous lampyridai of tropical America are very numerous and brilliant, in the words of Humboldt, repeating on the earth the spectacle of the starry heavens.
According to Gosse, their sparks, of various degrees of intensity, in proportion to the size of the species, are to be seen gleaming by scores about the margins of woods and in open places in the island of Jamaica. This writer describes may species, of which the most remarkable are pygolampis xanthophotis and photuris versicolor. P. xanthophotis is three fourths of an inch long and one third of an inch wide; the elytra are smoke-black; the thorax drab, dark brown in the centre; the abdomen pale, with the last three or four segments cream-white; the light is very intense, of a rich orange color when seen abroad, but yellow when examined by the light of a candle, and intermittent, lighting up a few segments or the whole hinder part of the abdomen. P. versicolor is a large species, with drab-colored elytra, less brilliant in its light and less rapid in its flight than the former species; the light is of a bright green hue; it frequently rests on a twig, gradually increasing the intensity of its light to the brightest, and then by degrees extinguishing it, remaining dark a minute or two, shining and fading again like a revolving light. Sometimes one species is attracted by the other, when the intermingling of the green and orange rays presents a very beautiful appearance.
Other smaller species, which fly in at the windows in summer in considerable numbers, have either a yellow or a green light. The little firefly seen in warm summer nights is a species of photuris; it is the male only that flies; the wingless female, seldom seen, a glowworm, emits a much brighter light; the larva, which resembles the female, is luminous, and, it is said, the eggs are also. Another native species is photinus pyra-lis, the larva of which feeds on soft-bodied insects and worms.-Two species of hemipterous insects, of the genus fulgora, are said by some authors to be luminous, though the greatest weight of negative evidence is against this statement; the snout in this genus is long, straight or curved upward, and the light is said to emanate from its extremity, whence their common name of lantern flies. The South American species (F. laternaria, Linn.) is a large and handsome insect, with wings varied with black and yellow; Mme. Merian asserts positively that the light from the head is so brilliant that it is easy to read by it; Count Hoffmannsegg, M. Richard, and the prince of Neuwied have denied the truth of this statement; but, from the positive assertion of the above lady, the general application of the name firefly to this species, and the possibility that the emanation of light may be perceptible only at certain seasons of the year, it may well be that the insect possesses luminous power.
It flies high, and hovers about the summits of trees. Another species (F. candelaria, Fab.), from China, of a greenish color varied with orange and black, with its long snout curved upward, is said to flit among the branches of the banian and tamarind trees, illuminating their dark recesses.-The causes which produce this light have been the subject of much discussion among naturalists; some lay the principal stress upon the influence of the nervous system, others upon the respiration, others upon the circulation; chemists have asserted the presence of phosphorus in the fatty tissue whence the light seems to issue, but there is no proof of this from analysis. The most recent writers agree that the luminous tissue is made up of fat globules permeated by numerous tracheae conveying air, with no traces of nerves or blood vessels, according to Dr. Burnett. It does not appear satisfactorily determined whether there may not be in this tissue phosphorized fats which give forth light on contact with oxygen, hydrogen, or nitrogen. Matteucci concludes from his experiments that the light is produced by the union of carbon of the fat with the oxygen in the tracheae, by a slow combustion, and without any increase of temperature.
The intermittence of the light is believed to depend on the movements of respiration, and to be entirely independent of those of the circulation, though Carus says that the light of the glowworm grows brighter with each fresh wave of blood sent to the neighborhood of the tissue. It is probable also that the nervous system has some influence on the light, though it may not be essential to its production; as in the electric fishes we find the physical and chemical elements necessary for the production of electricity, to a great extent independent of, yet brought into harmonious action and directed by, the nervous system, so in the luminous insects we may have the chemical elements necessary for slow combustion and the Production of light independent of this system, yet influenced and directed by it; the light may also be directly influenced by the action of the nerves on the respiratory function. The luminous substance grows brighter in oxygen, duller in carbonic acid, and shines even in the dead insect and under water.
It is said that there is no heat accompanying this light, though it he a true combustion and a combination of carbon with oxygen; this may be owing to the rudeness or imperfection of our instruments, or to the slowness or peculiarity of the combustion.
Cucujo (Pyrophorus noctilucus).