Spiders and penises are two things most people want to keep far, far apart. Until now. New research suggests that the venom of one aggressive arachnid could be used in future treatments for erectile dysfunction (that is, if it doesn’t kill you first).

Say hello to the Brazilian wandering spider (Phoneutria nigriventer), also known as the armed spider, or as the banana spider. With an over four-inch leg span, this South and Central American native normally creeps around banana plantations, although some have wound up in American supermarkets and Canadian grocery stores. Flaccid fellows beware: On top of severe pain, a single bite from this eight-legged foe can cause you to lose control of your muscles—and if it’s not treated, the bite can screw up your ability to breathe so much so that you slowly die of oxygen deprivation.With a sip of the anti-venom, though, you’d recover in a week. And truth be told, only 10 people out of 7,000 are known to have actually died from a bite. Survivors tell of experiencing painful erections that last for more than four hours—a medical ailment known as priapism.

It’s this ...