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Word of the Week: Cantharidin

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Welcome to Word of the Week! Stay tuned for a new word each Friday to amp up your nature vocabulary!

Cantharidin [kan-THAIR-a-din] (noun): An odorless, toxic fatty oil which is secreted by many species of blister beetles.

It’s Blister Beetle season again! There are lots of different blister beetles in the world, but the ones that have taken over OURSpace are Short-winged Blister Beetles (Meloe angusticollis.) Be sure not to touch them with your skin! When disturbed, adult blister beetles secrete cantharidin from their bodies.

Cantharidin can cause blistering on skin and is considered a poison at certain doses. Even 100 milligrams can be fatal to humans if ingested, and this amount can be extracted from just a few beetles! Humans used to crush and dry blister beetles and use that resulting mixture as a remedy for gout and arthritis. It was also used as a popular aphrodisiac known as Spanish fly. Because of its toxicity, it is no longer widely used in medicine.

An animal that does, however, continue to use Cantharidin is the white-breasted nuthatch! With limited numbers of tree cavities and lots of competition between animals for shelter and a safe nesting site, White-breasted nuthatches have been seen with Short-winged Blister Beetles in their beaks, “sweeping” them on the bark around tree cavity entrances. As such, the beetles are not being used by the bird as a food source but rather as a strategy to keep animals, like squirrels, away from the nest with the cantharidin that was smeared on the tree.

Keep and eye out for Blister Beetles on your next visit to High Park!