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SYFY WIRE entomology

Praying mantises stay alive by scaring the you-know-what out of predators

By Elizabeth Rayne
The Deadly Mantis, 1957

Behold the praying mantis. Its protuberant eyes and menacing claws that are always clasped as if in prayer, maybe to some unholy insect entity, look like they may be enough to drive any remotely hungry predator away. Even stranger is how the survival of so many species of mantis could have resulted from more nightmare fuel.

Are you hearing this in David Attenborough’s voice yet?

The Dead Leaf Mantis looks like a mashup of Jar Jar Binks and the biologically inaccurate but still epic Dilophosaurus from Jurassic Park — at least when it is putting on a terrifying startle display. Any other time, it could be mistaken for a dead leaf. Biologist Kate Umbers from the University of Western Sydney has been investigating the elaborate and often terrifying startle displays mantises put on to spook predators. She and her colleagues found that the element of surprise in their startle displays is what can really throw a predator. It has worked for at least 60 million years.

“[We are] the first to test for evolutionary processes that might be driving both behavioral and morphological traits in startle displays,” said Umbers, who co-authored a study recently published in Proceedings of the Royal Society B: Biological Sciences.

Most defenses against predators are thought to be built in, such as the uncanny resemblance of the Dead Leaf Mantis (Deroplatys desiccata) or the Orchid Mantis (Hymenopus coronatus) to exactly what they were named for, so long as they don’t move. So why do they sometimes make a scene instead of blending in? Mantis startle displays are some of the most theatrical in the insect world, often involving dramatic movements, flashes of color and even gaping mouths seemingly threatening to devour the enemy. Some are more showy than others. Not long after the extinction of the dinosaurs in the late Cretaceous, deimatic or startle displays in insects are thought to have appeared after the growth and spread of birds and other predators.

Umbers ventured into the mysterious world of startle displays to potentially find out what lies behind them. She studied 49 species of mantis to try and find out the motives of this bizarre bug when it came to deimatic behavior. There was surprisingly no correlation between a species’ primary defense, such as leaf or flower camouflage, and its startle display.

“Secondary defenses like startle displays are used when primary defenses fail, [which] could mean that species with greater complexity in their displays are so because they are more often identified as prey and attacked,” she said.

This is still a hypothesis that will require more data on the predator-prey dynamics of various species and the vulnerability of those species to the predators that hunt them. Another prediction was that startle displays would correlate with body size, since a larger mantis may be more likely to be seen, as well as provide a more substantial meal and possibly have more trouble escaping. There turned out to be no evidence that body size or shape impacted startle displays.

Monster Island

Other influences on the evolution of different mantis species might explain size, because even though predation was most likely what set off startle displays, female orchid mantises are believed to have grown large before they evolved their orchid-like morphology that disguised these vicious carnivores as they stalked large insects that pollinated the flowers.

What turned out to be correlated with startle displays were mantis lineages that emerged from a common ancestor. The more species in that lineage, and the more closely related they were, the more likely they were to have evolved fancier startle displays. That is believed to have kept these species from going extinct. Mantises whose species evolved alone tend to put on less flashy shows. Think Jurassic Park’s brachiosaurs chewing on leaves versus Dennis Nedry’s face-off with that Dilophosaurus.

The most frustrating obstacle for Umbers was finding out what stimuli trigger such behavior in mantises when many of them could go unnoticed as they are. It is nearly impossible to induce this behavior in a live specimen without knowing these triggers.

While recordings of this phenomenon in the wild are rare, and capturing one in action could mean years of searching, it would be hard to miss.