A most unusual encounter with a water strider

Until I spotted one during a recent woodland walk, I never imagined that a water strider could bring such a considerable measure of surprise, delight, and mystery into my adult life. But that’s exactly what happened when I met one of these common aquatic insects while hiking through Earthquake Park on the third Monday of April.

I have been aware of water striders since my boyhood days in Connecticut when I watched them skip and skate across the liquid surface of a neighborhood pond, just a long stone’s throw from my family’s yard.

I’m sure I felt some amazement when I first noticed their small streaking forms, and I’ve enjoyed watching their rapid, gliding movements upon water ever since those earliest encounters. But to be honest, I never thought much about the lives of water striders or the mechanics of their movements until now.

I also admit to some surprise when I discovered water striders inhabit Alaska’s ponds and lakes and wetland pools, though if I’d known more about them, I wouldn’t have been. Members of the Gerridae family are reported to occur widely throughout North America (and much of the rest of the world). But they never gained my attention the way some other northern insects like dragonflies, butterflies, bumblebees, and mosquitoes have.

All of that changed on my recent forest walk.

My day had begun on something of a low note. I felt unsettled, out of sorts, when I awoke that morning, and a vague feeling of unease stayed with me much of the morning and into the afternoon, fed in part by some computer and Internet problems and a friend’s unexpected request for help, in an area beyond my expertise. Nothing seriously awful happened, but I continued to feel some low-level anxiety and what I’d call an emotional “heaviness.”

I figured my daily walk with Denali would brighten my mood and lift my spirits. And it did. But what really changed the course of my day and pulled me out of the doldrums was that water strider.

While walking through a section of the woods that’s a small, boggy, ponded wetland in summer, I noticed a bug upon the still-abundant snow. At first glance and seen from a distance, it resembled a spider. However, on closer inspection, I recognized the creature to be a water strider. At least, I thought it to be one; its presence in the snow made me question my identification.

I’ve kept track of Anchorage-area insects and arachnids (mostly spiders and some daddy longlegs) throughout the seasonal round for many years, and I’ve documented several different species crawling or perched upon the snow in winter and early spring. But this was the first time I’d seen a water strider in such circumstances, whether living or dead. This one was clearly alive, as it demonstrated by skipping a short distance across the snow when gently nudged by my finger.

Because I knew them to be aquatic bugs, and no open pools of water had yet appeared anywhere nearby that snowy field, I wondered how in the world this water strider had come to be there.

It just didn’t make sense.

After the iNaturalist app on my iPhone confirmed the insect to be a water strider, I made it my mission to learn more about the critter.

I started by emailing Alex Wenninger, an entomologist with the Cooperative Extension Service’s Integrated Pest Management Program. She quickly responded with some helpful information, including a link to an online article about water striders, which explained, “During the winter, adults move to protected sites on land. Leaves, logs, holes in stream banks, or similar cover located near waterways are used for hibernation.”

Alex added, “My first thought is that perhaps it had overwintered in leaf litter somewhere nearby, where it warmed up and came out to find a water body.”

I never suspected that water striders spend their winters on land. So it made perfect sense that the strider I encountered—perhaps an early riser from winter’s dormancy—was seeking open water, and I happened to spot it crossing an open expanse of snow. Pretty darn amazing.

That prompted me to wonder what else I might learn about the lives of water striders, and I began an online search. Here’s another amazing thing: how easy it is nowadays to learn all kinds of information about our wild neighbors. Here I’ll share just a bit of what I’ve gleaned from various online articles and blogs, with more to come. As with other life forms, water striders’ body structures, abilities, and lifestyles are way more complex—and remarkable—than most of us humans imagine them to be.

To begin, more than 1,700 species of water striders have been identified around the world. At least five species are known to inhabit Alaska, though it seems likely others occur here, and they range from the Panhandle to the Arctic.

Though most commonly known as water striders, these aquatic insects are also variously called pond skaters, skimmers, water scooters, water skippers, and Jesus bugs (the latter because of their ability to “walk on water”).

It appears that the small narrow bodies of most water striders measure between a quarter and a half-inch long, supported by six legs of varying lengths. The longer middle and back legs propel striders across water and allow them to quickly shift directions and “put on the brakes” when necessary, while the shorter front legs are for catching and grasping prey.

Their ability to walk—or skip or skate—across water is possible because water striders have evolved legs that are covered by thousands of microscopic, grooved hairs. Those grooved hairs both repel water and trap air, which allows them to not only stand on the surface “membrane” of water but move easily and quickly across it. Studies have reportedly shown that they can move a hundred body lengths per second; researchers say a six-foot person would have to swim more than 400 miles an hour to match their speed. Wow!

As mentioned above, water striders are predatory creatures. They feed on flying insects that become trapped on the water’s surface or other aquatic insects that come to the surface for air. They have piercing mouthparts that inject paralyzing saliva that renders the prey helpless and helps to digest their tissue; the liquid is then sucked into the striders’ bodies—rather gruesome behavior for such lovely skaters.

There’s much more to be said about striders, including the details of their life cycles and unusual mating strategies. But for now, I’ll end with these strider curiosities: first, some water striders have wings while others don’t, depending on their circumstances.

And then there’s this: though buoyant, the legs and feet of water striders make dimples in the water surface they stand and skate upon. Those dimples act like lenses that refract sunlight. So when the sun is bright, and striders move upon clear, shallow waters, they may create dark, bulbous shadows on the pond bottom below. Sometimes, the shadows are more easily visible and more visually stunning than the insects themselves. And isn’t that a marvelous thing? It was almost as remarkable as finding a water strider skipping across the snowpack in early spring, searching for a pond of water to make its home.

Anchorage nature writer and wildlands/wildlife advocate Bill Sherwonit is a widely published essayist and the author of more than a dozen books, including “Living with Wildness: An Alaskan Odyssey” and “Animal Stories: Encounters with Alaska’s Wildlife.” Readers wishing to send comments or questions directly to Bill may do so at akgriz@hotmail.com