They Don't Eat, They Love Orgies: Meet the World's Most Romantic Moth

If there really were a mating manual for Phymatopus hecta, these would be among its entries:

Pendulation

Each night’s lek kicks off with males flying above the plants in a “pendulating” flight pattern. They seem to swing back and forth hypnotically in midair.

Scent Brushes

Males send out pheromones from fluffy yellow appendages on their back legs that look like curtain fringe. They fold these retractable brushes away at the end of each night.

Fanning

Females waft their own pheromones toward male suitors by flapping their wings like a courtesan’s fan.

Tenting and Spread-Eagling

Perching males may hang with their wings folded in a tent shape or held stiffly out from their bodies in what Turner calls the “spread-eagle display.” Both poses show off their handsome pattern of brown flecked with white.

Dance Fights

When two pendulating males get too close, they may fight. It’s more of a dance-off than a brawl. They either pendulate at each other head-on or hover a few centimeters apart, quivering, until one of them flees out of intimidation.

Mating Frenzy

A female who prefers the traditional moth mating style can simply perch and fan herself. Shortly thereafter, she may find herself swarmed by a dozen eager males at once.

Aerial Strike

In 1994, another researcher reported seeing a female gold swift dive-bomb a male in flight and take him to the ground for copulation. Turner never witnessed this.

Partner Dancing

Before they settle down to mate, the female and male sometimes pendulate together in a midair duet.

Homoeroticism

Very occasionally, males try to mate with each other. (It doesn’t work.) Turner says this behavior had him puzzled for years. But now he’s pretty sure that males just get confused by all the female pheromones floating around and try to copulate with the closest thing.

Copulation

The act itself is tricky—there’s no vanilla sex position for gold swifts. First, the female clings to a leaf by her front legs and dangles vertically. The male clambers onto her belly. Then he swivels to hang upside-down from the female, his body “held only by the grip of the genitalia.”

You should probably not try it at home, but this position helps keep mating moths safe. If a hungry wasp or spider comes close, the female simply lets go of her perch, and both lovers fall to safety in the brush below.

In fact, the clearing by Turner’s cottage may have become a popular lekking area because the plants that grow there have so many good copulation perches.

“It felt not as if I had found an interesting project, so much as that the moths had found me,” Turner says.

(Turner is a poetry translator as well as a biologist. He says there’s not as much overlap as you might think between the world of poetry and the complex romance of the gold swift. But writing scientific papers, with their rigid rules about formatting and language, reminds him of the 19th-century French sonnets he translates.)

The gold swift’s sex life is likely the most complicated in the insect world, Turner says. In this way, we can think of the moths like ourselves.

“Even though they have only pin-sized brains,” Turner says, the gold swift and its courtship habits “remind one of the considerable flexibility shown by humans.” He adds, “In other ways, of course, they are quite different.”

For example, the females only mate once in their lifetimes, fertilizing all their eggs in one go. And they don’t go on dinner dates. In fact, they don’t eat at all—their adult bodies are only made for mating.

“And, although it would be quite hard to prove it,” Turner says, “you can bet they don’t fantasize.”

Elizabeth Preston is a science writer in Massachusetts. Her blog, Inkfish, is published by Discover. Follow her on Twitter @Inkfish.

Illustration by Jim Cooke