The Spanish Fly is not a fly, it is a beetle. This beetle is crushed up and is then eaten. The cantharidin that it contains is supposed to work as a powerful aphrodisiac. However, it can be lethal. It is expelled from the body via urine, and it can make genitalia itch, swell and even leak bloody discharge. However, in some cases if the dose is too large Spanish Fly can cause fever, seizures, convulsions and ultimately death. Some love shops claim to sell potions that contain Spanish Fly but more often than not (fortunately) these potions are just imitations. The Spanish Fly did not just arrive on the aphrodisiac scene, in fact it dates all the way back to ancient Rome.