Water striders always come out on top.
They also stay on top! Water striders are those zippy, semi-aquatic insects that seem to magically skate along the surface of ponds, streams and other slow-moving waters. These above-water acrobats never plunge into the water or become submerged; they live on, not under, the surface of the water through their entire adult lives.
How do they do it? Isn’t walking on water a miracle only destined for the holy? Maybe not.
If you could examine a water strider under a microscope, you’d find unusual adaptations that enable this insect’s gravity-defying ways. You would take note, for instance, of the hairs that cover its legs. These microscopic hairs trap air, providing buoyancy that precludes a dip below the surface. A waxy secretion covers the water strider’s feet and repels water. The existing surface tension of the water also assists in holding this insect aloft. Water striders are a natural marvel.
Like all insects, water striders have six legs, and each pair has its own structure and function that help it accomplish its incredible feat.
The front pair of legs are small and folded and do not assist in locomotion. Instead, these legs are used to grasp prey and hold it while the piercing mouthparts of the water strider suck the juices and life from its captured meal. To locate their food, water striders use the surface of the water the way a spider uses a web: they can sense the water ripples that result from an insect that has fallen into the water and is struggling. Injured dragonflies are a favorite.
Getting to their prey is easy; theirs is true rapid transport. The water strider’s second row of legs acts as a pair of oars, and can propel them faster than you might guess. In just one second, the water strider can move 40 inches — farther than a yardstick — a distance that is, amazingly, one hundred times the length of their body! Don’t blink, or you might miss their motion. Directional guidance is provided by the third, or back, pair of legs, which also help to evenly distribute the weight of the insect.
With the advent of warmer temperatures, these insects have appeared in the Island’s fresh waters. Their winter was spent in hibernation under the leaf litter at the edge of the pond or in the nearby woods. Eggs will soon be laid by the female along the shoreline on twigs and plant matter. The insects that develop, though, will be different from their now active parents.
The adult water striders that emerge in the summer after the first spring mating are wingless, and will spend their entire life darting around the surface of the pond. The offspring of these wingless wonders come in the fall, and will be different still from their parents. They will have wings and with these appendages, the ability to fly. This skill skips a generation, and will be useful to allow these late-season water striders to fly to their hibernacula in the woods further inland from their pond.
Though they will never gain the fame of the other who has walked on water, water striders are still both impressive and graceful. Gliding along the pond’s surface, it is not too much to wonder if they are silently saying to themselves, “Feet don’t fail me now!”
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.