BLISTER-BEETLE. A dark-colored, elon gated beetle of the family Meloicke. so naiad be cause the dried and pulverized bodies of effillain of them are used to make blister-plasters. They are also called oil-beetles (q.v.), because some species, as of Melon, exude a disagreeable yellow fluid from the knee-joints when disturbed. In the adult stage these beetles occur on foliage and flowers, especially the goldenrod. and sev eral kinds are destructive to the potato-plant. The food habits of the young are very different from those of the parent. These beetles illustrate a method of insect development termed hyper metamorphosis. (See METAMORPHOSIS.) The best-known one is the eantharis. or Spanish-tly (Lytta resicatoria), of southern Europe, which is bright green, and about an inch long. It is gathered from its food-plants—lilac, privet, etc. —at night, when at rest, by heating the hushes and catching the insects in a cloth, by persons who guard their faces against the acrid volatile discharges of the beetles with veils and gloves. They are killed usually by immersion in hot vinegar and water. and then dried and put into air-tight bottles. Several other species of blister beetles are similarly used in other parts of the world.
The active principle of the blistering-flies is cantharidine, which possesses such pow erful properties that one-hundredth of a grain placed on the lip rapidly causes the rise of small blisters. Administered internally, blistering-flies cause heat in the throat, stomach, intestines. respiratory organs. etc.: and if in large doses, they give rise to inflammation of a serious na tore, and sufficient to cause death. Externally, they are employed as a blistering agent. There are various medicinal preparations of blistering flies, such as ecrate of eantharides, which con tains 320 parts of eantharides to ISO parts yel low' wax, 180 parts of resin, 220 parts of lard, and 150 parts of oil of turpentine: tincture of eantharides, procured by digesting blistering flies in proof-spirit. etc.; but that most com monly employed is plaster of cantbarides, or blis tering-plaster, obtained by heating and strain ing 80 parts of eerate of cantharides, and melting 1000 parts of Burgundy pitch with the strained liquid. See BLISTERS MELOID.E (for bibliog raphy) ; and illustration on Colored Plate of BEETLES.