CAN'THARIS (Gr. a small beetle, plural canthar'ides), a genus of insects of the order coleoptera, section heteromera. See COLEOPTERA. It belongs to a family called traehel ides, or necked beetles, the head being separated from the thorax by a distinct neck or pedicle, and forms the type of a subdivision of that family called coutharidke, many of the species of which possess blistering properties analogous to those of the common BLISTERING FLY, SPANISII FLY, or BLISTER BEETLE (U. vesicatoria). This insect, the best known and most important of the genus, is about an inch long; has a large heart shaped head, rather broader than the thorax; thread-like antenna three times longer than the head; a nearly quadrangular thorax; and soft elytra (wing-covers) concealing the abdomen, and of equal breadth throughout. It is of a bright glossy green color. The common blistering fly is found in the s. of Europe, and in the s. of Siberia. It is abundant in Italy, Sicily, and Spain, iu the s. of France, and in some parts of Germany and Russia. It is rare in England. The larva is not well known.. The perfect insect feeds on the leaves of the ash, privet, lilac, elder, and honeysuckle; and rests on them during the night, the day being its time of activity. It is therefore taken by beating the branches of the trees in the morning or evening, when it is comparatively lethargic, a cloth being spread below to receive the insects as they fall. The gathering of ides takes place, in the s. of France, in the month of 'May. It requires great caution to prevent injury to those who engage in it, the insects emitting a volatile substance with a strong smell, which causes inflammation of the eyes and eyelids, convulsive sneezing, and irritation of the throat and bronchial tubes, nor can they be handled without danger of blistering. Those who collect them, therefore, generally- wear
gloves and veils. Unpleasant effects have been experienced from even sitting under trees on the leaves of which cantharides were numerous. Various methods are employed for killing cautharides when they have been taken; the cloths containing them are very generally immersed in hot vinegar and water, and they are afterwards carefully dried: sometimes they are killed by the vapor of vinegar, and sometimes by oil of tur pentine. Unless kept with great care, they soon begin to lose their active properties, although, in stoppered bottles, they remain fit for use for years. They arc very liable to be injured by mites, and afford a favorite food also to a kind of moth and to sonic other insects. They are imported into Britain from the s. of Europe, and also from St. Petersburg.
The active principle of the blistering flies is cantharkline, possesses such pow erful blistering properties, 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 nature, and sufficient to cause death. Externally, they are employed as a blistering agent. There are various medicinal preparations of blistering flies, such as 'vinegar of cantharides, obtained by 'macerating blistering flies in acetic acid; tincture of cantharides, procured by digesting blistering flies in proof-spirit, etc.; but that most commonly employed is plaster of cantharides or blistering plaster, obtained by mixing equal parts of blistering flies, yellow wax, resin, and lard. See BLISTER.