I was on the dock at Camp Crabtree a few summers ago with my daughter and we watched a swarm of water striders, also known as Jesus Bugs or Pond Skaters, zig-zagging about for a long while. 

Her delight in their water skating ability took me back to days where I sat by the edge of a creek and watched their shadows, which looked like a small slender body surrounded by black circles.  When I tired of watching, I would try to scoop one up in my hand, which is a task on the level of catching a fly out of the air with chopsticks.

I briefly thought about telling my daughter how they stay on top of the water, but I believe it is better for her to just to first enjoy nature magic and draw her own conclusions.  The “magic” that allows them to stay afloat is the non-wettable hairs on their tarsi (feet), the lower half of their legs and the surface tension of the water. 

Basically, the spread weight of the water striders on the hairs of the feet and legs is not enough to overcome the attraction of the water molecules to each other.  This is also why you can oh so carefully place a needle on the surface of a glass of water and it will float.   If you allow either end to go under the surface, the needle will sink.  This is why the claws of water striders are not on the tarsi but located further up the leg, to ensure the surface tension is not broken by them.

National Geographic recently reported that each microscopic hair has a groove on them.  They wrote, “These grooves trap air, increasing water resistance of the water strider’s legs and overall buoyancy of the insect.”  How cool.  Childhood tests of sizable rocks thrown in the water beside them showed that they could easily remain buoyant even in explosive waves. 

The striders move by rowing the middle and back legs.  For slow movements, they use just the middle legs, but if they really need to move, as for catching a prey item, they use both the middle and hind legs together.  These middle and hind legs have vibration sensors that help the water striders effectively “read” the ripples in the water.  The ripples could mean predators or prey.  The front legs are greatly shortened and are used mainly for grasping and handling prey items.  

Prey items are aquatic and terrestrial.  The water strider eats terrestrial insects that get caught on the surface of the water and catch aquatic insects that come to the surface to breathe.  They also eat mosquito larva that have breathing tubes on the surface.  

Water striders are in the order Hemiptera or the “True Bugs” and they have piercing mouth parts that puncture through prey and then suck it in.  When not in use, the mouthparts are tucked between their “chin” and “chest”. 

Toward the end of fall, water striders fly to nearby wooded areas and spend the winter under the litter of the forest.  In spring, they return to the water with females laying eggs on floating objects.  The nymphs start their lives on the surface, eating whatever comes by until they molt five times and become adults. 

So, the next time you find your doctor telling you that you need to relax, not be so tense, just remember to tell him/her that you, like the water strider, thrive on tension. 

Know more to see more,

Ranger Billy