Male praying mantis fights to avoid being eaten

Sexual reproduction in the insect world is often a risky business and never more so than when the risk of being eaten is high.

Female praying mantis credit: Nathan Burke

But a new study on South African - or Springbok - praying mantids, commonly found in New Zealand after first being identified here in the 1970s, shows the male of the species has developed a highly unusual strategy to avoid being consumed by the female.

The Springbok mantis (Miomantis caffra) is one of a number of insect species where sexual cannibalism by the female is common. Previous studies have shown that more than 60 per cent of sexual interactions end in males being consumed, mostly without mating.

Different insect species employ different tactics to try and avoid that fate, such as approaching females when they are feeding or moulting, using a decoy nuptial gift or playing dead when females attack.

But this study shows the male praying mantis will engage in violent physical struggle with the female to try and successfully mate, and the strategy appears to work: the majority of males who managed to both successfully copulate and avoid being eaten engaged in physical struggle with the female.

“It is rare for males to avoid cannibalism by this form of coercion – physically fighting with females in order to successfully mate – and this is the first evidence of this behaviour in a cannibalistic mantis,” says University of Auckland Research Fellow Nathan Burke.

“Sexual conflict in the insect world is not that unusual and usually favours a cautious or tactical approach but the male Springbok mantis really does fight to achieve his goal and this study shows that might be his best option in terms of reproductive success.”

The research, from Dr Burke and Associate Professor Gregory Holwell of the University of Auckland’s School of Biological Sciences, involved collecting 52 pairs of Springbok mantis and observing their behaviour in the laboratory over a 24-hour period.

They found 29 out of the 52 pairings (56 per cent) resulted in physical contact between the sexes with the male always first to initiate contact. Almost all - 90 per cent - escalated into physical struggle with 58 per cent of males who managed to grab the female first ending in successful mating. Half were subsequently eaten.

A low 7 per cent of pairings resulted in no clear winner from the physical contest, 35 per cent resulted in the female winning the initial physical confrontation and eating the male while 20 per cent of pairings resulted in no mating and no cannibalism.

Another unusual finding of the research was that 27 per cent of females that lost the physical struggle were injured by the male’s foretibial claws, resulting in severe abdominal puncture wounds that later formed black scabs – something also observed in females in the wild.

“We have learned a lot of fascinating biology from Miomantis caffra over the last decade, but this latest work is truly amazing,” says Associate Professor Holwell. “This is the best example out there of males fighting back to help cope with the risk of sexual cannibalism.”

The research is published in Biology Letters.

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