Praying Mantises Falling Victim to Sex Cannibal

By James Owen

The only praying mantis native to New Zealand has developed a fatal attraction for a cannibal invader whose females devour its mates after sex, scientists report.

Males of the New Zealand mantis (Orthodera novaezealandiae) are being seduced into serving themselves up as meals to females of the springbok mantis (Miomantis caffra), a study published November 26 in the journal Biology Letters has revealed.

praying mantis picture
Orthodera novaezealandiae, New Zealand’s native praying mantis. Photograph by Michael Lidski/Alamy

The findings suggest the native males are falling victim to the deadly charms of the invasive South African species because they find the scent of its females irresistible.

Watch a video of a female eating a male.

The discovery was made during an investigation into an unexplained decline in the endemic New Zealand mantis by biologists from the University of Auckland.

“The cause of the decline is suspected to be Miomantis caffra, but until our study there was no data on their interactions,” co-author Greg Holwell said in an email.

Loved to Death

Mindful of the African interloper’s sexually cannibalistic tendencies, the team paired both sexes of the two species up in the lab to see how they got on.

Like other insects such as moths, praying mantis females often use airborne sex pheromones to entice a mate, and previous studies have shown there can be a degree of overlap in these pheromones between different species.

The study team therefore focused on the relative allure of sex pheromones released during their cross-species matchmaking.

Surprisingly, in 11 out 13 cases, New Zealand mantis males found the scent of springbok mantis females more attractive than their own females’ perfume, according to the study. (See “Praying Mantis Mimics Flower to Trick Prey.”)

For most of them this proved fatal—69 per cent of such pairings concluded with the male being eaten.

A male New Zealand mantis attempts to mate with an invasive female mantis. Photograph courtesy Murray Fea

Springbok mantis males, which naturally have more experience with the deadly females, fared better, with 39 per cent becoming dinner.

Since New Zealand praying mantis females “are not sexually cannibalistic, or at least rarely so, males will not have evolved to be as cautious in their approach as males of sexually cannibalistic species such as M. caffra,” Holwell observed.

Deadly Pheromones

Since the sex pheromones of mantises can carry over long distances, a single springbok mantis female could potentially put significant numbers New Zealand mantis males out of reproductive action.

Conversely, the study team noted, the native mantis’ loss is likely the aggressive invader’s gain, given the nourishing stream of besotted males their females have to gorge on. (See “Wild Romance: Weird Animal Courtship and Mating Rituals.”)

The study team suspects there could be more examples of such gruesome cross-species sexual interactions out there in the insect and arachnid world.

“The consequences for naïve native species exposed to sexually cannibalistic invaders are likely to be particularly dramatic,” Holwell concluded.