Orchid-like insect uses petal-shaped legs to glide

The orchid mantis, Hymenopus coronatus, is well-known for its specialized shape and color — like a pinkish-white orchid flower — and has long been considered a fine example of floral mimicry.

While some research had already confirmed that the masquerade helps the mantis attract prey, the function of its petal-shaped legs — actually two pairs of petal-like extensions on its middle and hind legs — remained uncertain.

The mystery has now been solved by a research team led by Chen Zhanqi from the Chinese Academy of Sciences’ Xishuangbanna Tropical Botanical Garden, that found the mantis can use its petal-shaped legs for gliding.

In the study published online in the journal Current Biology on Nov 29, the scientists conducted behavioral research and found that orchid mantises are excellent gliders.

“The petal-shaped femoral lobes are just like wings, playing a crucial role in gliding,” said Chen, one of the article’s corresponding authors.

He said orchid mantises that fell from a height of 10 meters could glide an average distance of 6.1 meters, with the farthest recorded glide reaching 14.7 meters. However, when the femoral lobes were removed, the orchid mantis could only glide an average horizontal distance of 4 meters, and anesthetized individuals could only fall vertically.

Morphological analysis showed that the cross-section of the femoral lobes was curved, matching the curvature of gliding structures in other animals and the wings of birds. The study revealed that the femoral lobes across different age stages gradually grew larger and rounder. In older nymphs, the femoral lobes occupy a larger proportion of their body area.

“Through this adjustment, even though a final-stage individual weighs 165 times more than a first-stage nymph, they can achieve similar gliding distances,” said Zhao Xin, a doctoral student at the botanical garden in Yunnan province, who was the first author of the paper.

She said the femoral lobes were the first reported obvious gliding structures found in arthropods. The proportion of body surface area occupied by the femoral lobes was significantly larger than that of other gliding arthropods, and its gliding ability surpassed that of all known arthropod gliders. “They are the most adept arthropod gliders known to date,” she said.

Compared to vertebrates such as flying squirrels, gliding lizards, and flying frogs, which have membrane-like structures for gliding, arthropods have exoskeletons composed of rigid chitin, making it challenging for them to retract specialized appendages.

This results in decreased mobility and a higher susceptibility to predators.

As a result, arthropods such as the orchid mantis, leaf insects, and certain shield bugs, which possess such structures, often employ survival strategies such as camouflage.

“Our study suggests that the demands of gliding may have been one of the important driving forces for the evolution of prominent specialized appendages and coloration in larger arthropods, which may be accompanied by other defensive strategies,” Chen said.

Source: xtbg.cas.cn