DERIVATION.--Cantharides is obtained from flies which receive the name
Spanish Fly on account of so many of them coming from Spain, but they
are also imported from Germany and Russia; living chiefly on climbing
shrubs and trees.
DESCRIPTION.--About 20 to 25 m. m. long and about 6 mm. broad, flattish
cylindrical, with filiform antennae, black in the upper part, and with
long wing-sheaths, and ample membranous, transparent, brownish wings,
elsewhere of a shining, coppery-green color. The powder is
grayish-brown, and contains green shining particles. Odor strong and
disagreeable; taste slight, afterwards irritating. Cantharides
deteriorate with age and should be kept unpowdered in tightly stoppered
bottles.
DOSE.--Of the powdered fly, horses and cattle, 5 to 10 gr.; sheep and
pigs, 3 to 6 gr.; dogs, ¹⁄₂ to 2 gr.