Fig. 536.—Tetracha bifasciata.
The tribe of Tenebrionidæ, called formerly Melasomas, because they are nearly all black, resembles in some points the Carabici. They seek after dark places, and avoid the light, and are found on the ground under stones; their movements are slow, and they walk with difficulty. The best-known insect of this group is the Blaps, of repulsive smell, inhabiting dark damp places, such as cellars, and only coming out of its retreat during the night. The elytra are joined together, and they have no wings. The vulgar regard them as an omen of ill-luck. [Fig. 541] represents the Blaps obtusa. According to the report of a traveller, the women in Egypt eat the Blaps sulcata cooked with butter, to make them fat. They are employed also against the ear-ache, the bite of scorpions, &c.
Another genus of the same family is the Tenebrio ([Fig. 542]), of a blackish-brown, with the elytra striated, and of half an inch in length. The larvæ, the well-known meal-worms, live in flour; they are cylindrical, and of a light tawny colour ([Fig. 542]). The insect which is considered as a type of the tribe of the Pimelides is the Pimelia bipunctata, which is common in the south of France.
| Fig. 537—Manticora tuberculata. | Fig. 538.—Pogonostoma gracilis. |
We come now to the tribe of blistering beetles, of which the best known is the Cantharides (Cantharis or Lytta). These insects are generally of soft consistency, and their elytra very flexible. A few remain constantly on trees. All are very brisk and active. When swallowed they are a dangerous poison, but are used in medicine for making blisters.
| Fig. 539.—Ctenostoma rugosa. | Fig. 540.—Therates labiata. |
| Fig. 541.—Blaps obtusa. | Fig. 542.—Tenebrio molitor (larva and imago). |
The Cantharides of commerce (Cantharis [Lytta] vesicatoria) are of a beautiful green, attain to a size of four-fifths of an inch, and are found on ash-trees, lilacs, and other shrubs. Commerce for a long time brought them from Spain, and some still come from that country; hence the common name of Spanish fly. As they live in great numbers together, collecting them is easier and less expensive than would be that of other species of the same family which are not gregarious, but which have the same medicinal properties. The presence of the Cantharides is manifested by the strong penetrating odour which they diffuse to some distance. When, by aid of this smell, they are discovered, generally settled on an ash, they are collected in the following manner:—Very early in the morning a cloth of light tissue is stretched out at the foot of the tree, and the branches are shaken, which causes the insects to fall ([Plate XII.]). These, numbed by the cold of the night, do not try to escape. When there is a sufficient quantity, the four corners are drawn up and the whole plunged into a tub of vinegar diluted with water. This immersion causes the death of the insects. They then carry them to a loft, or under a very airy shed. To dry them they spread them out on hurdles covered with linen or paper, and from time to time, to facilitate the operation, they are moved about, either with a stick or with the hand, which is more convenient; but it is then necessary to take the precaution of putting on gloves, for, if touched with the naked hand, they would cause more or less serious blisters. The same precaution must be observed in gathering them.
When the Cantharides are quite dry, they put them into wooden boxes or vessels of glass or earthenware hermetically sealed, and preserve them in a place protected from damp. With these precautions, they may be kept for a long while without losing any of their caustic properties. Dumeril made blisters of Cantharides which had been twenty-four years in store, and which had lost none of their energy. When dry, they are so light that a kilogramme contains nearly 13,000 insects. Aretius, a physician who flourished at Rome in the first century of our era, seems to have been the first to employ Cantharides, reduced to powder, as a means of vesication. Hippocrates administered them internally in cases of dropsy, apoplexy, and jaundice. But it is pretty nearly established that the Cantharides of the ancients were not the same species used at the present day; they were, probably, a kindred species, the Mylabris chicorii. A blistering principle has been extracted from these insects, called Cantharadine. This organic product presents itself under the form of little shining flakes, without colour, soluble in ether or oil. One atom of this matter applied to the skin, and particularly to the lower lip, makes the epidermis rise instantaneously, and produces a small blister filled with a watery liquid. In spite of the corrosive principle which the Cantharis contains, it is attacked, like other dried insects, by the Dermestes and the Anthrenus, which feast on them without suffering the smallest inconvenience.