Blister Beetles: Do Not Take Internally

Blister beetles consume rhubarb chard overnight

We enjoyed my brother-in-law’s rhubarb chard for supper Monday night (in southern Missouri). Tuesday morning, Ann came back inside from the raised bed where it was growing with a look of horror on her face. Here’s why.

Overnight, the 4 x 4 foot patch had been discovered by a legion of 3-striped blister beetles. It was almost as if they had emerged out of the soil. There were probably 2 – 3 hundred of them, and they had eaten or spoiled with their droppings the entire planting. There was nothing to do but to spray them with Sevin, and everything above the soil will have to be cleared away and put in a safe place where other animals can’t get to it.

The poison from these beetles that creates the blistering for which they are named is called cantheridine, and it is extremely toxic. You can find all sorts of dire warnings about horse fatality if consumed even a small amount of dead beetles, especially in alfalfa where the beetles might get baled into the hay.

If you happen upon this beetle, leave it alone and don’t let your kids handle it. If they do, be sure and wash their hands well. The toxin is persistent long after the beetle dies, so even dead beetles are a threat.

This is the mythical “Spanish Fly” we heard about in high school, but thankfully, did not have access to for its purported aphrodisiac properties. Here’s what Wikipedia contributes about it uses:

Early uses

Medical use dates back to descriptions from Hippocrates. Plasters made from wings of these beetles have been used to raise blisters. In ancient China, the beetles were mixed with human excrement, arsenic and wolfsbane to make the world’s first recorded stink bomb.[6]

Various preparations of desiccated Spanish flies have been used as some of the world’s oldest alleged aphrodisiacs, with a reputation dating back to the early western mediterranean classical civilizations:
  • In Roman times, Livia, the scheming wife of Augustus Caesar, slipped it into food hoping to inspire her guests to some indiscretion with which she could later blackmail them.[7]
  • Henry IV (1050—1106) is known to have consumed Spanish fly at the risk of his health.
  • In 1572, Ambroise Paré wrote an account of a man suffering from “the most frightful satyriasis” after taking a potion composed of nettles and cantharides.[8]
  • In the 1670s, Spanish fly was mixed with dried moles and bat’s blood for a love charm made by the magician La Voisin.[9]
  • It was slipped into the food of Louis XIV to secure the king’s lust for Madame de Montespan.
  • In the 18th century, cantharides became fashionable, known as pastilles Richelieu in France.
  • The Marquis de Sade is claimed to have given aniseed-flavored pastilles that were laced with Spanish fly to prostitutes at an orgy in 1772. He was sentenced to death for poisoning and sodomy, but later reprieved on appeal.[10
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Fred First holds masters degrees in Vertebrate Zoology and physical therapy, and has been a biology teacher and physical therapist by profession. He moved to southwest Virginia in 1975 and to Floyd County in 1997. He maintains a daily photo-blog, broadcasts essays on the Roanoke NPR station, and contributes regular columns for the Floyd Press and Roanoke's Star Sentinel. His two non-fiction books, Slow Road Home and his recent What We Hold in Our Hands, celebrate the riches that we possess in our families and communities, our natural bounty, social capital and Appalachian cultures old and new. He has served on the Jacksonville Center Board of Directors and is newly active in the Sustain Floyd organization. He lives in northeastern Floyd County on the headwaters of the Roanoke River.

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  1. The natural world is strange and even more so the human world, as that Wikipedia example illustrates. Wow. Never heard of any of this (except good old Spanish Fly, heard about by every teenager, back in the 50’s.)

  2. You learn something new every day. They look more like lightening bugs than flies.

    I’ve been told also to wash hands after squishing Colorado Potato Beetles because the yellow/orange pigment they leave behind can be toxic.

  3. Blister Beetles do look like lightning bugs! Thanks for posting Fred, I too had no idea about these creatures. I’m battling flea beetles on my cabbage, broccoli, and brussel sprout plants. Despite their now lacy looking leaves, the broccoli and cabbage are still producing. Now I’m going to make sure that flea beetles don’t leave behind anything toxic! We already ate one harvest of broccoli though, and we’re fine so far!