Certain mantis species, like Kongobatha diademata, flatten their bodies against leaves, a practice called leaf-planking
Ruth S (CC-BY-NC-ND 4.0)
Some mantises can taste leaves with a newly discovered sensory organ: a strange, bristly bump projecting from their chests.
This “gustifolium” is unlike anything seen in mantises or any other predatory insects, say the researchers who made the discovery. It may have evolved to aid certain mantises’ extremely specialised lifestyles.
Some praying mantis species found in Asia and Australia engage in “leaf-planking”, flattening their bodies against the underside of leaves as they cling, motionless.
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“They pretty much do everything from these leaves,” says Josh Martin at Colby College in Maine. “They use them as perches, they hunt from them, males often fly off looking for females from them.”
Researchers previously noticed that some leaf-planking species had a curious, circular chest projection not found in other mantises. Martin and an international team of researchers took a closer look at the anatomical oddity in a few Australian leaf-planking species. They used high-powered X-rays and multiple types of microscopes to examine the structure inside and up close.
The gustifolium is studded with 14 to 25 stiff hairs, making it look a bit like a spiky pimple. Inside, the researchers discovered, it is filled with nerve cells.
A scanning electron microscope image of the gustifolium, a bristly bump found on the chests of some praying mantis species
Sydney Brannoch
In laboratory experiments, the electrical activity of these neurons increased when the structure was exposed to compounds plants release into the air. This suggests the hairs are taste sensors like those found on the feet, legs and mouthparts of other insects. By touching or simply hovering over their perches, the mantises seem to be tasting those leaves.
“The evolution of a unique and specialised organ for sensing is a big deal for an organism,” says Martin. So it probably plays an important role, possibly telling the insects what type of leaf they are on or how suitable it is as a hunting perch, he adds.
The discovery may have unexpected implications for mantis conservation, says Roberto Battiston at the “G. Zannato” Museum of Archaeology and Natural Sciences in Italy. If the link between leaf-planking mantises and their favourite foliage is species-specific, the disappearance of host plants due to deforestation or other habitat changes could have a “massive impact” on these mantises, says Battiston.
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