SEPTEMBER
1993

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

9-09-93

Water Striders Thrive on Tension

There are insects that live on land. There are insects that live in water. There is also a group of insects that live ON water. Most people know these insects as water striders.

Water striders glide across the surface of water with the ease and grace of a professional skater on an ice rink. Hence, they are sometimes called skaters. Other people refer to these insects as Jesus bugs because of their ability to walk on water. Pond skimmer is another common name for this insect.

Almost everyone at some time has observed water striders on the surface of a pond, puddle, or creek. “How do they do that?” is a common question. The answer is surface tension, that tendency of water or other surface molecules of a liquid to cling to each other. The adherence is strong enough so that things such as needles, as many of us have discovered in early science experiments, will float if the surface tension isn't broken. Water striders don't break the surface tension, so they stay high and dry — unless someone manages to dunk them with a stone or splash of water.

Water striders spend their entire lives depending on surface tension to keep them afloat. They lay eggs in plant material under the surface of the water, but as soon as the young striders hatch, they surface and begin to skate. Both young and adult water striders feed on small animals, including insects and newly hatched tadpoles, on the water's surface.

These insects are ruthless predators. They grasp their meals with their forelegs, insert their beaks, pump in digestive juices that turn the innards of their victims into a kind of soup. They then suck up their food as if they are sipping soda through a straw.

One group of water striders lives on the surface of the oceans. These insects, known as sea skaters, are one of the few insects associated with salt water. Generally salt water is left to insect relatives such as lobsters, shrimp, and crabs. While most sea skaters live near the shore, a few have learned to survive on the open seas in warm areas of the Atlantic, Pacific, and Indian oceans.

Water striders are one of the insect groups that sometimes have wings and sometimes do not. Even the winged individuals look wingless to the casual observer. However, some individuals do fly. That is how they end up in every water puddle following a summer rain. After all, no puddle is too small for a demonstration of free-form skating by water striders.

 

 

Writer: Tom Turpin
Editor: Andrea McCann