Photograph by Piotr Naskrecki

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In the insect order that grigs share with grasshoppers and katydids, there are three North American grig species—found primarily in the forests of northwestern U.S. and southwestern Canada.

Photograph by Piotr Naskrecki

The First Time

Basic Instincts: A genteel disquisition on love and lust in the animal kingdom.

For humans, sexual initiation can be a big deal—obsessed about, romanticized. The loss of virginity, it's said, leaves one forever changed.

"Tell me about it," says the male hump-winged grig. The first female he mates with takes not just his innocence but bites of his body.

Grigs are cricket-like insects whose annual mating season involves what behavioral ecologist Scott Sakaluk calls "an unusual form of sexual cannibalism." To entice a female grig, a male makes a call by rubbing his forewings together, an act called stridulation. The male then seals the deal by letting the female munch on his hind wings during sex and lap up the hemolymph, the bug version of blood. "One night he's a virgin. The next night he's been chewed on," Sakaluk says.

Why do some males get several of these grisly trysts (which are seldom, if ever, fatal) but others get none? The call is key. When Sakaluk's colleague Geoff Ower compared the insects' calls, he found "fundamental differences" between the sound made by grigs that had mating success and those that did not.

Being a sex snack can sap the strength a male grig needs for stridulation, Sakaluk says. By the end of mating season, "there's only a few left calling. Those are the males that have gotten superlucky—and they are chewed right down to the nub."

The feature Basic Instincts: A genteel disquisition on love and lust in the animal kingdom appears every month in National Geographic magazine.