Strong sticking power and quick reaction time help the insects stay put in trees

By Susan Milius

Web edition: February 27, 2013

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LAUGHING AT GRAVITY

An Asian weaver ant (Oecophylla smaragdina) can dangle a weight more than 100 times heavier than itself without losing its grip on the surface above it.

Credit: © Thomas Endlein

An Asian weaver ant boasts not one but two superpowers: Its extreme sticking power comes with extraordinarily quick emergency grip protection, researchers have discovered.

The ants nest in trees, which they hold onto with their moist, expandable foot pads. The moisture isn’t a glue, but it lets the foot pads hold tight using capillary forces, the same phenomenon that allows water-soaked paper towels to cling to a window. When a branch quivers in the wind, an ant’s foot pads expand, strengthening their grip. By observing the pads of ant feet as the surface they stood on shook, Thomas Endlein of Scotland’s University of Glasgow discovered that the foot pad expansion occurs within a millisecond of the jolt.

The fastest known nerve response takes five or 10 milliseconds, so the quick grip must be mechanical. Too fast to be a reflex, it’s a preflex, Endlein and a colleague report online February 27 in the Proceedings of the Royal Society B.