Wood-eating cockroaches aren’t the only creatures that make a meal out of their mates, but their motivations may be unique.

“Cannibalism is quite frequent in spiders,” said María José Albo, an evolutionary biologist at the University of the Republic in Uruguay. Among sexually cannibalistic spiders and insects such as praying mantises, it’s usually a larger female who eats her mate. Although on the surface it seems like a bad outcome for the male, he may benefit by transferring more sperm while the female dines, Dr. Albo said.

On a less gruesome note, Dr. Albo added, some male insects and spiders give their mates a so-called nuptial gift: food that’s sometimes made from the male’s own body. The gift may buy him more time to mate — or to escape.

All of these cases involve only one mate being fed, Dr. Albo said, which makes the cockroaches so unusual. “If the mutual wing-eating has fitness benefits for both sexes, it will be the first case of mutual gift-feeding,” she said.

Those benefits probably aren’t nutritional, Ms. Osaki and Dr. Kasuya wrote, because the cockroach wings aren’t fleshy. But the roaches probably do benefit from losing their wings, because wings are cumbersome when living in tight quarters. Wings can also collect mold or mites, the authors wrote.

“It makes sense that there’s an advantage to getting rid of your wings if you’re not going to fly ever again,” said Allen J. Moore, an evolutionary biologist at the University of Georgia. Some other insects that live underground or inside wood also shed their wings after mating, such as termites, close relatives that Dr. Moore called “just fancy cockroaches.”

But these insects have to lose their wings on their own. “This mutual helping is just really unique,” he said.

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