Paris (AFP)

The approach is brutal, but they have no choice: some male praying mantises hurt their partner to force her to mate, thus avoiding having her head cut off before marrying, as some females have the annoying habit of doing. , according to a study published Wednesday.

These insects are known for their conflicting sexual practices, where it happens to the female to decapitate the male before, during or after the act of reproduction, to better devour him, and recover the energy necessary for his future laying.

This "sexual cannibalism" also exists in certain spiders where, as in the mantis, the aggressor sex is larger and stronger than the attacked sex.

The phenomenon is particularly widespread among the "Springbok" mantis (Miomantis caffra), living in particular in New Zealand: in 60% of sexual interactions, the unfortunate males are consumed before they have even been able to copulate.

In terms of evolution, females of this species have no reason to curb their ferocious appetite because they are able to self-fertilize their eggs, and therefore do without Monsieur - a single-parent mode of reproduction called "parthenogenesis" .

A team of biologists, whose work is published in the journal Biology Letters, logically wondered how males could continue to exist under such hostile conditions.

They collected adult specimens of "Miomantis caffra" in New Zealand, to pair 52 "pairs" in transparent boxes for 24 hours, in order to closely follow the progress of the antics.

- "Sexual coercion" -

Result: it is always the male who went in contact, leaping on the female.

She attacked him in return, and then a fight ensued where each sex tried to dominate the other, grabbing it with its ravishing paws.

In 35% of the fights, the female won and consumed her prey.

But in the majority of cases - almost 60% - it was the male who took the upper hand.

Once his partner was neutralized, he forced her to mate to fertilize her eggs.

His tactic: piercing his opponent's abdomen with his anterior claws, a non-fatal wound causing loss of hemolymph (fluid that acts as blood for invertebrates), and leaving a black scar on the female's body.

"I was very surprised that they hurt them to mate. Nothing like this had never been observed in the mantis", tells AFP Nathan Burke, specialist in the evolution of the sexes in animals at the University of Auckland.

The study concludes that the males who lost the battle were systematically eaten, while the victors greatly increased their chances of copulating and escaping cannibalization (some individuals still ended up swallowed up after the love affair).

This strategy of "sexual coercion" is quite common in animals (insects, reptiles, fish, mammals), but rare in a species engaging in sexual cannibalism.

"Probably because in this case, the females are much larger, and submitting to their force is too dangerous," says Nathan Burke.

This "sexual dimorphism" generally prompts the male to be extremely careful when approaching his partner - as if playing "Russian roulette".

It can wait, for example, until it has its back turned or that it is busy tasting another prey before trying its luck.

The aggressive approach of Mr. Mantis "Springbok" is therefore surprising.

Is she an exception among the nearly 2,000 species of mantis?

"We ignore it at this point. Maybe others are behaving like this, but no one has watched yet," the researcher concludes.

© 2021 AFP