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Desert Diary

Arthropods/Water Walking


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The ability to walk on water often is attributed, somewhat facetiously, to the great and powerful. Of course, this loses somewhat of its impact in the north, where anyone can walk on water during the wintertime. But down in our desert, where it's seldom cold enough to form thick ice, it truly would seem to be impossible. Yet, observe along the edges of ponds or irrigation ditches, and you just might see creatures walking on water.

We often forget that we're giants and our relationship with the environment is quite different from those of smaller beings. Our great weight prevents us from walking on liquid water, but such creatures as water striders are light enough to not break through the water's surface tension. In a sense, water molecules are sticky, and at the water's surface, the pull of other water molecules is so uneven that the top layer sticks together like a thin, rubber membrane. This allows the unwettable legs of the water strider to support itself, just as if it were moving across a surface of soft Jello.

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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.