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Naïve males fall prey to sexy female invaders

The phrase “she bit my head off” takes on a whole new meaning if you’re a male New Zealand praying mantis with mating in mind.

An alarming proportion of our native males are being devoured by South African females, which lure their prey to destruction by exuding an irresistible erotic scent.

The more delicate New Zealand male approaches the exotic female enthusiastically, lacking the caution of male South African praying mantises which have an in-built wariness when wooing their aggressive potential mates.

Recent research from University of Auckland behavioural ecologist Dr Greg Holwell demonstrate that after approaching the sexy cannibalistic invaders, around 70 percent of our naïve native males are killed and eaten.

It’s a cruel twist, this fatal attraction. Our males find the foreigners more attractive than the home-grown variety, yet it’s impossible for them to mate with the exotic species - so they die in vain.

Our females are also likely to miss out because there are not enough native males left to mate with them and – the ultimate irony – our hapless males feed the predatory females.

Greg says our native praying mantises are officially “at risk” and we need to actively get rid of the overseas interlopers. Putting them in the freezer is a recommended approach, but it’s important to know which species is which.

The South African praying mantises are larger – the females often have large, swelling bellies (full of our native males, no doubt) and the necks of both males and females are noticeably narrower than their heads. Our natives have necks nearly as thick as their bodies and they also have distinctive blue-purple patches on the inside of their front legs.

The decline of our native species was thought to be linked with competition for food, a theory which did not sit well with Greg, and the results of his latest research point to direct predation in the context of sexual cannibalism as a likely culprit in the decline of natives.

This research has attracted international attention and a University of Auckland study led by Greg’s Masters’ student Murray Fea, with assistance from Greg and his colleague Dr Margaret Stanley, was recently published in the journal Biology Letters.

Greg has been studying praying mantises for 12 years. His interest in creatures big and small started early in his childhood. He read about animals from an early age and it was a natural progression to start studying them in his native Australia.

After getting his first degree, he started out with mammals – platypuses and kangaroos – moving on to praying mantises when he started work on his PhD.

“I began looking at a range of different praying mantis species in Australia and became particularly interested in the cannibalistic reproductive behaviour of some of them,” he says.

Greg’s research uncovered a number of new species and new behaviours, including the finding that for some species, females have more offspring when they eat their mates providing a direct benefit to females.

Greg has also been part of a study into pollinator deception in the beautiful Malaysian orchid mantis recently published in the journal The American Naturalist. The mantis mimics orchid flowers, attracting and then eating, the insects that come to pollinate them.

Field experiments in the shared University of Auckland and Macquarie University (Sydney) study showed that isolated orchid mantises attracted wild pollinators at a rate even higher than flowers, and captured them as prey.

“After more than a century of conjecture, we provided the first experimental evidence of pollinator deception in the orchid mantis and the first description of a unique predatory strategy that has not been documented in any other animal species.”

ENDS

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