cantharides

noun2

1. •
   Spanish fly, Lytta vesicatoria (syn. Cantharis vesicatoria).
2. •
   Spanish fly; a vesicant extracted from the beetle, popularly held to have aphrodisiac properties.

   • I can make the most subtle sauces yield up their secret—whether it be white arsenic, rosalgar, mercury sublimate, or cantharides. — 1926