Insects "Walk On Water" Upside-Down Beneath The Surface

[EnolaGaia]

There aren't many insect species that can walk or skate across a water surface. Researchers have now identified and reported species of insects that do the same upside-down (i.e., they are submerged and tread the water / air interface from below). Such capabilities had long been noted among certain specialists, but it seems nobody thought it merited examination.

These beetles walk on water, upside down, underneath the surface

Surface tension allows for insects like water striders to skate along the top of still waters, for example. But new research reveals an unusual way to tread along this boundary: from the underside.

A water-dwelling beetle can scuttle upside-down along the underside of the water’s surface, as if the water were a solid pane of glass, researchers report June 28 in Ethology. It’s the first detailed documentation of a beetle moving in this manner, which is known only in precious few animal groups. ...

FULL STORY (With Video): https://www.sciencenews.org/article/beetles-walk-on-water-upside-down-underneath-surface

 

[EnolaGaia]

Here are the bibliographic details and abstract of the published report.

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Locomotion with a twist: Aquatic beetle walks upside down on the underside of the water's surface
John Gould, Jose. W. Valdez
Ethology. First published: 28 June 2021
https://doi.org/10.1111/eth.13203

Abstract
While animals generally move through the aquatic environment by propelling themselves through the water or walking on submerged substrates, some have evolved the unique capacity to move along the water–air interface. This is because cohesive forces between water molecules cause the surface to be in tension, providing a physical substrate that can be used for support and pushed against for horizontal movement. Herein, we report on the use of the underside of the water's surface for locomotion in an unidentified Australian beetle (likely family: Hydrophilidae). Field observations revealed that the beetle was able to rest and move along the surface of an ephemeral pool inverted without penetrating the surface above. The beetle possessed a layer of trapped air along its abdomen and moved forward by walking, with deformations of the water's surface apparent each time a leg made contact. This appears to be the first visual evidence illustrating the ability of aquatic beetles to directly rest and walk on the underside of the water's surface. We propose that the air bubbles located on the abdomen and/or legs may be providing the upward force necessary for the beetle to be pushed against the underside of the water's surface. The water's surface seems to be acting as a support for the beetle, with the force needed for forward movement generated by the beetle's legs as each transition between the stance and swing phases of walking. Our work adds to the small number of observations of animals using the underside of the water's surface to move and highlights the likely importance of surface tension for locomotion on either side of the water–air interface.

SOURCE: https://onlinelibrary.wiley.com/doi/10.1111/eth.13203

 

[Coastaljames]

Interesting thank you @EnolaGaia.

I've always been fascinated by Water Striders!