Water Striders

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Loren Eiseley said, "If there is magic on this planet, it is contained in water." I have to agree. Clouds, waves, glaciers, rainbows, snowflakes, babbling brooks, thunderous waterfalls, geysers, hoarfrost, dew and even hot tubs are all miraculous manifestations of this glorious liquid.

But of the many wondrous properties of water, one of the most striking is surface tension. Because water molecules at the surface are not totally surrounded on all sides by other molecules, they adhere more strongly with the ones they are in contact with. This creates a film of tension at the surface. One common critter that has taken full advantage of this tension is known as the pond skater in Canada, the Jesus bug in Texas, but mostly as the water strider.

These insects exploit the surface film to scoot about on the water, and fast! They can traverse three feet in only 1.5 seconds, paddling with two pairs of legs several times the length of their body! The sensitive hairs on the smaller front legs feel ripples from struggling insects. This is basically how spiders also detect their prey trapped in webs. Water striders capture aquatic insects and other invertebrates that are attracted to water.

There are 500 or so species of water strider worldwide, 60 in North America and about 10 different kinds in California. Remarkably, water striders are the only insects to have colonized the open ocean.

The most common species is Gerris remigis. This species has wings (many species do not) which enable it to fly and colonize the most remote and temporary ponds. Consequently this is the most successful and widespread species in North America.


I suspect that many of you, like me, have spent fruitful hours watching the antics of these enchanting insects. I especially enjoy their marvelous shadows cast on the bottom of a still pool. There is indeed magic in water.

This is Michael Ellis with a Perspective.