快猫短视频

The key to a monogamous relationship is cannibalism 鈥� at least for wood-feeding cockroaches. This behaviour has probably evolved so these insects can keep partners around to help raise offspring.

Most cases of sexual cannibalism involve creatures like spiders eating their suitors after mating. Males are often the victims, and eating them could help females fatten up on nutrients for use during pregnancy. Some male spiders will even sacrifice legs to aggressive females during mating.

But males cannibalising females is rare, and mutual cannibalism even rarer. The case of this wood-eating cockroach species may be one of the only known examples of a species that practises mutual sexual cannibalism, says Haruka Osaki at Kyushu University in Japan.

Osaki first noticed chewed wings on wood-feeding cockroaches (Salganea taiwanensis) that she caught in forests in Okinawa 鈥� the roaches range from Amani Island in Japan to Taiwan. To examine the phenomenon more closely, she and her colleagues collected wild cockroaches, divided them into 24 pairs, and video recorded them for three days in enclosures. They found that 12 of the pairs took turns consuming each other鈥檚 wings after mating.

The cannibalism was usually preambled by a little foreplay in the form of licking, and the recipients didn鈥檛 appear to resist the love bites when they came, say the authors. The team also noted that the wings lack flesh, so wouldn鈥檛 provide much in the way of nutrition.

鈥淭his wood-feeding cockroach must benefit somehow because this behaviour has evolved and maintained,鈥� says Osaki.

Osaki and her colleagues aren鈥檛 sure why, but they have a few ideas. These cockroaches usually mate with one partner for the duration of their life and stay together to raise multiple broods in galleries inside rotting wood.

Clipping each other鈥檚 wings may encourage both partners to stick around to help raise offspring, especially as they are more easily exposed to predators outside their log. Or it could help them move around more easily in tight passages without getting stuck. Ridding themselves of body parts that can attract mites or mould might also help keep their brood cleaner and safer.

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