Wood-eating cockroaches aren’t the only creatures that will turn their pals into a meal, but their motivations may be unique.

“Cannibalism is pretty common in spiders,” said María José Albo, an evolutionary biologist at the University of the Republic of Uruguay. Among sexually cannibalistic spiders and insects like praying mantises, it’s usually a larger woman who eats her partner. Although on the surface it may seem like a bad result for the man, he can benefit from transferring more sperm while the woman is feeding, said Dr. Albo.

Less cruel, added Dr. Albo added, some male insects and spiders give their companions what is known as a wedding present: food that is sometimes made from the man’s own body. The gift can buy him more time to mate – or to flee.

In all of these cases, only one partner will be fed, said Dr. Albo, what makes the cockroaches so unusual. “If wing eating has fitness benefits for both sexes, it will be the first instance of mutual gift giving,” she said.

These benefits are likely not nutritional, wrote Ms. Osaki and Dr. Kasuya because the cockroach wings are not meaty. But the cockroaches will likely benefit from losing their wings because wings are awkward in tight spaces. Wings can also collect mold or mites, the authors wrote.

“It makes sense that getting rid of the wings if you never fly again is beneficial,” said Allen J. Moore, an evolutionary biologist at the University of Georgia. Some other insects that live underground or in wood also lose 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 help is just unique,” he said.