The Spanish fly is an emerald-green beetle in the family Meloidae, Lytta vesicatoria. It is 15 mm to 22 mm long and 5 mm to 8 mm wide, and lives on plants in the families Caprifoliaceae and Oleaceae. The beetle contains up to 5% cantharidin which irritates animal tissues. The crushed powder of Spanish fly is of yellowish brown to brown-olive color with iridescent reflections, of disagreeable scent and bitter flavor.Spanish fly, or cantharides as it is sometimes called, is often given to farm animals to incite them to mating. The cantharides excreted in the urine irritate the urethral passages, causing inflammation in the genitals and subsequent priapism. For this reason, Spanish fly has been given to humans for purposes of seduction. It is dangerous since the amount required is minuscule and the difference between the effective dose and the harmful dose is quite narrow. Cantharides cause painful urination, fever, and sometimes bloody discharge. They can cause permanent damage to the kidneys and genitals.