The natural source of cantharidin is not fire-colored beetles but rather a group of beetles generally known as blister beetles. They owe their blistering reputation to cantharidin, which causes severe irritation of the skin when touched -- and of the urogenital tract when swallowed. Because of its purported stimulative effect, cantharidin was one of the first natural compounds to undergo scientific investigation, beginning early in the 19th century when it was chemically isolated. In that century French entrepreneurs harvested thousands of blister beetles to produce Spanish fly aphrodisiac (although most of their beetles came from China and not Spain).
The medical literature, while skirting the question of Spanish fly's efficacy as an aphrodisiac, does chronicle an unfortunate side effect for human males: "erections douloureuses et prolongues," in the words of a French Foreign Legion physician who observed soldiers suffering painful, prolonged erections (or priapism) after eating frog-legs from amphibians that ate blister beetles. Cantharidin is not only painful but toxic, and as little as 20 blister beetles' worth can be fatal to humans, Eisner reported in a 1990 article in the journal Chemoecology.
Repeated tests in the Cornell laboratories demonstrated that male Neopyrochroa beetles without cantharidin are unlucky in love. When males that hadn't been fed cantharidin attempted to mate, the females checked their heads for the compound and, finding none, curled their abdomens and rebuffed their advances.
"Isn't it ironic that a compound with a misplaced reputation in human sexual behavior is actually used for a sexual purpose by
Contact: Roger Segelken
Cornell University News Service