Glowworm , a name given to several serri-corn beetles, constituting the genus lampyris (Fab.). The antenna) are short, with cylindrical and compressed articulations; the head is concealed beneath the anterior margin of the thorax; the eyes and the mouth are small; the body is rather soft and depressed, with the sides of the abdomen serrated; the elvtra are coriaceous and slightly flexible. The females are wingless, with rudiments of elytra at the base of the abdomen, and their general appearance to the uneducated eve is that of a worm, explaining fully the popular name of glowworm in England, and ver luisant in France. In the old Linnaean genus lampyris there were as many as 60 species, which have been distrib-uted into different genera, so that there were only nine species left in the genus in the last edition of Dejean's catalogue. There are four well known species of glowworm in Europe, L. noctiluca, Italica, splendidula, and hemip-tera ; the second is probably the species whose luminous faculty was known to the ancients, the of the Greeks, and cicindela of the Romans. Both sexes are luminous, though the light is stronger in the female; the light does not come from the thorax as in the firefly (elater), but from the posterior part of the abdomen on its upper and under surfaces. The English glowworm (L. noctiluca, Linn.) is the largest European species, about two thirds of an inch long in the male, and the female about an inch; the male is brownish gray, with a reddish gray margin on the superior portion of the thorax, and has both wings and elytra; the female is wingless, of a uniform yellow white, with a very thin skin below; in both sexes the luminous spots show themselves as four bright points, two on the antepenultimate abdominal segment, and two on the next posterior. The L. Italica is next in size, and is found in southern Europe, as the first is in the northern countries; the color is black, with red prothorax and legs; both sexes are winged, and much resemble each other, the apterous females spoken of by some entomologists being the larva). The L. splendidula is common in Germany; the male is winged, brown gray, with a bright glassy spot on the convex margin of the prothorax; the female, whitish yellow with a brown spot on the centre of the prothorax, has no wings, and very short oval elytra; the luminous spots are two transverse bands on the lower surface of the two penultimate abdominal segments, and in the female the whole abdomen diffuses a weak light.
L. hemiptera, a southern species, and the smallest one third of an inch long, is opaque black, lighter in the female, the posterior ventral plates being whitish; the males have truncated elytra, the females none; the light is diffused from two round spots on the penultimate segment; the larva) are probably luminous, as those of the preceding species were found to be by Burmeister. The first three species conceal themselves in the daytime and appear at night, the males flying about in the warm summer evenings, while the females betray their situations by their tranquil light among the shrubs; the last species creeps also by day, especially in damp weather, appearing toward the end of April; the third species occurs about the end of May and the beginning of June, while the first is found most abundantly toward the end of summer. The light is greenish or more commonly bluish white, intermittent or continuous at the will of the insect, extinguished in time of danger, and increased by active motion, sexual excitement, or artificial heat; it may continue some hours after death, and when lost may be reproduced by warm water; poisonous gases destroy the light with life, while oxygen increases its brilliancy; electricity produces no effect on the light, while galvanism increases or reproduces it in dead insects.
The researches of Kolliker and others show that at the shining spots is a whitish, transparent, fatty mass, permeated by very numerous trachea); this mass will shine when removed from the body, and in warm water for a long time, and its particles rubbed upon the fingers display a light resembling that from phosphorized mixtures. The eggs of the glowworm, the larva), and the nymphs, are luminous; the eggs are hatched after a few weeks, and the larvae resemble the perfect females, having a body of twelve segments, the first three of which bear each a pair of feet; the head is small, and, like the caudal segments, retractile; they thrive well in captivity when kept in moist earth or herbage, and supplied with slugs and snails, which they kill with their arched and sharp-pointed jaws, and eagerly devour; about a week is occupied in assuming the state of nymph, and in about eight days longer they appear as perfect insects. The nymph is larger than the larva, but not quite so long; the color is at first pale yellow, with two reddish spots on the posterior part of the thorax and the segments, but the dull color of the perfect insect is visible toward the end of the nymph state; the larval jaws disappear, and the antennas are seen to have eleven joints, and the tarsi five; the last abdominal rings are very brilliant, and indeed the whole body seems phosphorescent.
According to Dufour, the alimentary canal of the perfect female is twice as long as the body, and the oesophagus exceedingly short, immediately dilating into a short crop. - The substance from which the luminous property is derived has been often made the subject of experiment, but as yet, according to Matteucci, without the detection of any phosphorus in it, though the circumstances attending the light resemble the conditions under which phosphorus is luminous, being increased by warmth, diminished by cold, and destroyed by irrespirable gases, oil, alcohol, acids, and strong saline solutions; these phenomena admit of a better explanation on Matteucci's theory. This author, in his Lecons sur les phenomenes physiques des corps vivants, explains all cases of animal phosphorescence on physico-chemical principles. From his experiments we know that the light of the glowworm may cease before the death of the animal, or may be considerably prolonged after this event; that the light is without heat, as far as our rude instruments can detect; that it ceases soonest in carbonic acid, and in hydrogen in from 30 to 40 minutes; that it is increased in oxygen, and lasts three times as long as in other gases, both for parts and for the entire insect; that it consumes a portion of oxygen, which is replaced by carbonic acid, and is therefore the product of a true combustion; that when not shining, and in contact with oxygen, none of this gas is taken up, and no carbonic acid is formed; that heat to a certain extent increases, while cold diminishes its brightness; that when the luminous substance has been altered by too great heat or the action of gases so as to lose its phosphorescence, this property cannot be reestablished; finally, that carbon and not phosphorus is one of the elements of this substance, and that the phosphorescence is produced by the combination of the carbon with the oxygen.
The luminous matter from the living insect, according to the same author, has a peculiar odor resembling that of the perspiration of the feet; it is neither acid nor alkaline, dries rapidly in the air, seems to coagulate in contact with dilute acids, is not sensibly soluble in alcohol, ether, or weak alkaline solutions, but is dissolved in concentrated sulphuric and hydrochloric acids with the aid of heat; chemical tests exclude the idea of the presence of albumen, and the ordinary ammoniacal products are disengaged by heat. The oxygen of the atmosphere introduced by the numerous tracheae comes in contact with this substance, sui generis, composed principally of carbon, hydrogen, oxygen, and nitrogen. The intermittence of the glowworm's light, and its sudden changes from darkness to brightness, as far as present investigations go, are dependent on the different amounts of air introduced into the tracheae, and the varying activity of respiration and muscular action. The change in the food of the glowworm, from animal juices in the larva state to tender plants in the perfect condition, explains the contradictory statements of authors as to the habits of this insect; and the failure of the attempts to introduce it as an ornament to shrubberies and lawns has generally arisen from ignorance of the fact that the larva cannot be raised on vegetable food alone; besides moist herbage or damp earth, minute land shells must be supplied. - A few specimens of an articulated animal which may be called a glowworm have been found of late years in summer in various parts of southern New England. The head is small and flat, with very short antennae; the color is cream-white, the length about 14 lines, and the whole of this is lighted up at night with a permanent lumi-nousness less than that of the elaters of the West Indies; the light begins to show itself between the segments, of which there are 12, and at the stigmata, from which it spreads until the whole animal is illuminated, seeming a stick of light without joints or stigmata ; most brilliant soon after midnight, they gradually fade to the ordinary whitish color at daybreak. - In all these cases of phosphorescent articulates it is difficult to say what is the precise purpose of the light. (See Firefly.)
Glowworm (Lampyris splendidula). 1. Male. 2. Female. 3. Larva of L. noetiluca.
Glowworm (Lampyris noctiluca).