Another genus of this family is Meloë, with very short elytra, and without wings. They walk slowly and with difficulty on low plants, the female dragging along an enormous abdomen filled with eggs. They are generally observed in spring. In Germany they give them the name of Maiwurm (Mayworm). Their succulence would expose them, without doubt, to the voracity of birds and of insect-eating Mammifers if they had not the power of exuding at will, in the moment of danger, from all their articulations, an unctuous humour of a reddish-yellow colour, the odour and probably also the caustic properties of which repel the aggressor. The females lay their eggs underground, and out of these come forth larvæ of a strange shape. Swallowed by cattle, they cause them to swell and die. It is for this reason that Latreille has given it as his opinion that these insects are the Buprestis of the ancients, of which the law of Cornelius speaks, "Lex Cornelia de sicariis et veneficis." But the name of Buprestis was applied by Linnæus to a genus of which we shall treat farther on, and it has been generally adopted by naturalists.
| Fig. 545.—Sitaris humeralis. | Fig. 546.—First larva of Sitaris humeralis (magnified). |
The commonest among the Meloës is the Meloë proscarabæus, which is to be found in abundance, in the month of April, in the meadows near the bridge of Ivry in the environs of Paris. The metamorphoses of the insects of this family had remained for a long time surrounded with an impenetrable veil of mystery, but the researches of Newport in England, and of M. Fabre (of Avignon) in France, has made known in our days, phases, extremely curious, under which are accomplished the metamorphoses of the Meloë cicatricosus, and of the Sitaris humeralis, a species which belongs to the same family.[126] These observations, of which we are about to give a rapid summary, will probably help towards unravelling the first states of Cantharis.
| Fig. 547.—Pseudo-nymph of Sitaris humeralis. | Fig. 548.—Third larva of Sitaris humeralis. | Fig. 549.—Pupa of Sitaris humeralis. |
The Sitaris humeralis ([Fig. 545]) takes no nourishment when arrived at the perfect state. When the female has been impregnated, she lays at the entrance of the nest of a solitary bee from 2,000 to 3,000 small whitish eggs, stuck together in shapeless masses. A month afterwards there come out of these eggs very small larvæ, of a shiny dark green, hard-skinned, armed with strong jaws, and long legs and antennæ ([Fig. 546]). These are the first larvæ. They remain motionless, and without taking food, till the following spring. At this period are hatched the male bees, which precede the appearance of the females by a month. As the bees come out of their nests, these larvæ hook themselves on to their hairs, and pass them to the females, at the coupling period. When the male bees have built the cells, and furnished them with honey, the female, as we know, deposits in each an egg. Immediately the larvæ of the Sitaris let themselves fall on these eggs, open them, and suck their contents. Then they change their skin, and the second larva appears. This one gets into the honey, on which it feeds for six weeks. It is blind, whereas the first larva was provided with four eyes, no doubt to enable it to see the bees which were to serve as its conductors, in like manner as the companions of Ulysses watched the sheep of Polyphemus, so as to escape out of the cave in which they were retained as prisoners. A few days later, and this second larva contracts, and detaches from its body a transparent skin, which discloses a mass, at first soft, which very soon hardens, and becomes of a bright tawny colour; it is called the pseudo-nymph ([Fig. 547]). It goes through the winter in this state. In the spring comes forth a third larva ([Fig. 548]), resembling the second. This one does not eat, and moults after a time. It very soon changes into an ordinary pupa ([Fig. 549]), of a yellowish-white, from which comes forth the adult Sitaris, which lives only a few days, to ensure the propagation of its species, as is observed in the case of the Ephemeræ. The larvæ of the Sitaris had for a long time been remarked clinging on to the hairs of the Anthophoras, but they were always taken for Acari, and they had been described as such.
Fig. 550.—Lampyris noctiluca (male and female).
The Lampyridæ have the elytra weak and soft, like the insects of the preceding tribe. In their perfect state they frequent flowers. The larvæ are carnivorous, attacking other insects or worms. It is to this group that the Lampyris noctiluca, or glow-worm, which one sees shining during summer nights on grass and bushes, belongs. It has the power of making this natural torch shine or disappear at will.
The luminous properties with which these insects are endowed have for their object to reveal their presence to the opposite sex, for the females alone possess these properties. In the same way as sounds or odours exhaling from some insects attract the one towards the other sex, so with the Lampyris a phosphorescent light shows the females to the males. The seat of the phosphorescent substance varies according to the species. It exists generally under the three last rings of the abdomen, and the light is produced by the slow combustion of a peculiar secretion. It has been stated that it is evolved quickly when the animal contracts its muscles, either spontaneously or under the influence of artificial excitement. Some chemical experiments have been made to ascertain the nature or the composition of the humour which produces this strange effect; but up to this moment, they have only enabled us to discover that the luminous action is more powerful in oxygen, and ceases in gases incapable of supporting combustion. In the most common species, the Lampyris noctiluca, or glow-worm, the phosphorescence is of a greenish tint: it assumes at certain moments the brightness of white-hot coal.