Wood-eating cockroaches aren’t the only creatures making their partner’s meal, but their motivations can be unique.
“Cannibalism is quite common 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 is usually a larger female that eats her mate. While on the surface it may seem like a bad outcome for the male, he may benefit from transferring more sperm while the female is eating, said Dr. Albo.
In a less gruesome tone, Dr. Albo adds, some male insects and spiders give their partners a so-called wedding gift – food that is sometimes made from the man’s own body. The gift can give him more time to mate – or to escape.
In all these cases, only one partner is fed, said Dr. Albo, which makes the cockroaches so unusual. “If eating wings reciprocally has fitness benefits for both sexes, it will be the first instance of reciprocal gift feeding,” she said.
Those benefits probably aren’t nutritious, Ms Osaki and Dr. Kasuya, because the cockroach’s wings are not fleshy. But the cockroaches probably benefit from losing their wings, as wings are inconvenient when living in tight spaces. Wings can also collect fungi or mites, the authors wrote.
“It makes sense that losing your wings if you never fly again is an advantage,” said Allen J. Moore, an evolutionary biologist at the University of Georgia. Some other insects that live underground or in the woods also shed their wings after mating, such as termites, close relatives that Dr. Moore called “just beautiful cockroaches.”
But these insects have to lose their wings on their own. “This mutual aid is just really unique,” he said.