A dangerously exciting beetle – the Spanish Fly

Recently I obtained an ancient sample from a pharmacy in the Netherlands, a small jar filled with green beetles.

the Spanish Fly

As you can see, they are not all in one piece anymore. But I was told that I should still be able to identify which species it was, well challenge accepted!! Not much later I was indeed able to find which species I was dealing with, the Spanish Fly (Lytta vesicatoria). Which of course is not a fly at all but a beetle. After a bit of research I figured out what a jar of beetles was doing in a pharmacy, and decided it was well worth it to write about it.

“In 1772, the Marquis de Sade got an orgy going with the help of Spanish fly-laced candy.” – Secrets from the Sex Lab, Judy Dutton

Cantharidin the Aphrodisiac

As the quote above indicates, the Spanish fly was used to extract a substance (Cantharidin) which can be used as an aphrodisiac (like viagra). So far so good, pretty exciting beetles! You can find Spanish Fly aphrodisiac in stores all over the world, also in the Netherlands. It is even thought that Cantharidin can help against cancer.

Cantharidin the lethal poison

There is more to this story than meets the eye. The Spanish Fly is part of a family of blister beetles (Meloidae), and they didn’t get the name blister beetle by giving men erections. When the human skin is exposed to cantharidin it causes blisters. But blisters are the least of your worries when dealing with cantharidin! When taken orally, this substance is lethal at a concentration of 0,5 mg/kg of the bodyweight. Which means that for a adult male of 80 kg, 40 mg of cantharidin is lethal. It can furthermore cause:

  • Liver poisoning
  • Kidney failure
  • Circulatory collapse
  • Painful erections
  • Impotence

And as if that isn’t enough, the substance doesn’t increase lust, but only induces an erection. So then you’re stuck with a raging erection which you don’t even want to use… On the positive side, it can be used to remove warts.

My advice? Just stay away from it! The products with cantharidin sold as aphrodisiac generally do not contain enough to do anything, although they might give a nice placebo-erection. But for the upcoming valentine’s day, just go with candlelight, wine and Barry White.


Cantharidin: Als Potenzmittel entzaubert, aber… (2013) Anna Rudo, Hans-Ullrich Siehi, Klaus-Peter Zeller, Stefan Berger, Dieter Sicker. Chemie in unserer Zeit, Volume 47, Issue 5, pages 310-316.