These Cockroaches Practices Mutual Cannibalism Post-Coital Bliss

For some cockroaches, telling their mate, they love them might involve some mutual cannibalism post-coital bliss. This wood cockroach, Salganea taiwanensis, take turns with their partners to chew each other's wings down to stubs before they start raising their family, The New York Times reported.

Scientists say that this unique behavior may have evolved because wood roaches have a monogamous bond. Haruka Osaki, the author of the study published in Ethology last month, said that this post-coital mechanism was first observed in 2014 on wood roaches.

Osaki had been collecting insects from the woods in Japan as a hobby when the wood-feeding cockroaches caught her attention. "I noticed that their wings were chewed by something," Osaki said. 

When it was time for her to choose a topic for her doctoral research, she thought of the cockroaches as she knew that the damage on their wings did not come from predators. Her research adviser Eiti Kasuya encouraged her to pursue the research, and so she went to the Okinawan forest to collect some wood roaches.

(Photo: Ethology)
Adults of Salganea taiwanensis before (right) and after (left) mutual wing‐eating behavior. The right individual has long, intact wings. The left individual has short wings. Most of its wings has been eaten by its mate Osaki and Kasuya, Ethology, 2021

The Key to A Monogamous Relationship is Cannibalism

For wood-feeding cockroaches, cannibalism is the key to a monogamous relationship that involves couples taking turns eating each other's wings.

Sexual cannibalism is usually seen in insects like praying mantis. Still, the sexual cannibalism between wood roaches is different as both the female and male take part in the cannibalistic behavior.

During Osaki's experiment, she noticed that after the wood roaches mate, they remained motionless for over a third of the time while their partner ate their wings. Then the recipient "violently shook its body left and right" to get their partner to stop chewing. 

She noted that almost half of the specimens would continue to feast on all four wings until they are completely gone. This behavior is considered unique; usually, only the female is involved in the cannibalistic behavior and not the males. So far, no mutual cannibalism has ever been observed in the wild.

It suggests true monogamy, wherein the behavior of one partner benefits the other partner and vice versa.

ALSO READ: Female Anglerfish Absorbs Males During Mating

Why Do They Eat Each Other's Wings?

According to ScienceAlert, the researchers believe that the wing-eating cannibalism behavior between the wood roaches may have something to do with grooming than eating. Since wings are not made of flesh, chewing wings do not provide much nutritional value.

Authors believe that this could be their way to increase their mate's survival so they both can raise their young for years on end without the possibility of one of them committing betrayal.

Therefore, a pair of adult flightless cockroaches would stay in their log to avoid predators, ensure their fidelity, and help each other to raise their young. They consider this as the most loving act for cockroaches.

RELATED TOPIC: Male Praying Mantis Developed A Mechanism To Avoid Decapitation After Mating

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