Photographs by Rebecca Hale, NGM Staff. Beetles courtesy Jonathan Lelito, USDA. Decoy courtesy Akhlesh Lakhtakia and Stephen Swiontek.
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The decoy (second from right) is a literal femme fatale: a fake female beetle wired to deliver a lethal electric shock.
Photographs by Rebecca Hale, NGM Staff. Beetles courtesy Jonathan Lelito, USDA. Decoy courtesy Akhlesh Lakhtakia and Stephen Swiontek.

When Sex Is Shocking

Male beetles trying to mate with this decoy female get 4,000 fatal volts of electricity.

This story appears in the September 2016 issue of National Geographic magazine.

An emerald ash borer hovers, checking out the female forms below him. He’s drawn by how light plays across their bodies. He picks one, approaches, initiates physical contact—and is zapped by 4,000 volts.

Trying to mate with an electrified decoy is a grisly way to go. But entomologist Michael Domingue has no qualms about killing the emerald ash borer, or EAB for short. Since 2002 EABs have killed hundreds of millions of North America’s native ash trees.

To catch them, Domingue and his Pennsylvania State University colleagues created a literal femme fatale: a faux female, battery-powered so it would lethally shock any male that mounted it. The scientists made a rough version of the decoy on a 3-D printer; EAB males looked but didn’t land. The researchers also made a more realistic model, with a similar emerald hue and light-scattering surface texture as a real EAB shell. In tests using both real dead females and high-fidelity decoy females, virtually the same number of EABs alighted on each.

Placing decoy-baited traps in areas not yet affected by EABs could help scientists detect the beetle’s spread in time to attempt preventive measures. “If we know sooner where it’s showing up,” Domingue says, “there might be more we could do about it.”