Male mantises fight females to mate – but they get eaten if they lose

Female praying mantises are famous for attacking and cannibalising their mates during or after a sexual encounter, but evidence is emerging that some males attack too, and that winning a fight is crucial for successful mating.

Sexual cannibalism is common amongst praying mantises. Typically, the female is the aggressor, which encourages males to approach the female carefully and cautiously when mating. But Nathan Burke and Gregory Holwell at the University of Auckland, New Zealand, say some male praying mantises go on the attack instead. They wrestle and sometimes seriously injure the females in an attempt to mate and avoid being eaten.

The two researchers studied 52 pairs of Miomantis caffra, commonly known as the springbok mantis, in the lab for 24 hours. During the first 12 hours, they watched the insects carefully to see which pairs fought, and which member of each pair “won” the fight. Over half of the praying mantis pairs had a fight within the first 12 hours.

“These struggles were always initiated by the males and involved bouts of violent wrestling where each sex tried to be the first to pin down the other,” says Burke. He and Holwell think that the males were trying to use force to encourage the females to mate.

At the end of the 24 hours, Burke and Holwell recorded if the insect pairs had mated or whether the male had met its demise.

It turns out the outcome was dependent on who won the fights recorded within the first 12 hours. If the female won the fight, she always cannibalised the male. But if the males won, mating was the most common outcome.

“It seems that many females would rather eat a male than mate with one,” says Burke. It’s no surprise that the females are in no hurry to mate, as M. caffra females are able to reproduce asexually without sperm.

In four of the fights that Burke and Holwell observed, the male praying mantis used its dagger-like claws to strike the female, inflicting a wound that leaked plenty of bodily fluid. “Sex is rarely a bed of roses, even at the best of times. But for praying mantises, it’s a deadly game,” says Burke.

“I’m surprised we don’t see this more often, given that males are well equipped with raptorial forelimbs designed to catch and hold insect prey,” says William Brown at State University of New York at Fredonia.

Journal reference: Biology Letters, DOI: 10.1098/rsbl.2020.0811

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