Page:The American Cyclopædia (1879) Volume VII.djvu/222

 214 FIREFLY tiluca, L. Italica, L. splendidula, and L. Jiemip- tera, will be described under GLOWWOKM. In the United States there are many species, of which the L. scintillans (Say) and L. corusca (Linn.) are familiar examples. The latter is 4f lines long ; the body is oblong pubescent, brown- ish black ; a rose-colored arched streak, dilated and yellower anteriorly, joins the elevated tho- racic 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 larvae of many species, and also the eggs, are luminous. Like the elaters, they conceal themselves by day, and fly about in warm damp evenings; the males fly from plant to plant, while the female remains still, betraying her- self to the other sex by her brighter light, of a bluish or greenish white tint. The luminous lampyridm of tropical America are very numer- ous 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 many species, the most remark- able of which are pygolampis xanthophotis and photuris versicolor. P. xanthophotis is three fourths of an inch long and one tnird 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 yel- low 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 ex- tinguishing 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. Oth- er 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 pJiotu- ris ; 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 in- sects 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 Holfrnannsegg, M. Richard, and the prince of Neuwied have denied the truth of this state- ment ; 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 pro- duce this light have been the subject of much discussion among naturalists; some lay the principal stress upon the influence of the ner- vous 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 re- cent writers agree that the luminous tissue is made up of fat globules permeated by numer- ous tracheae conveying air, with no traces of nerves or blood vessels, according to Dr. Bur- nett. It does not appear satisfactorily deter- mined 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 influ- ence on the light, though it may not be essen- tial 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