Judy Larch, age 11, of Houston, Texas, for her question;
How does a water bug stay on the water?
It is summer and the water ballet is in full swing. Admission is free, but you must get yourself to the brink of some pond or quiet stream. A pair of opera glasses or binoculars will give you a more detailed view of the finer steps. A magnifying glass is handy in case you get a chance to look at one of the tiny performers at close range.
The star of the show is the spidery looking strider, also known as the water skater or the Jesus bug. Small midges and gnats also alight on the water to waltz a few graceful steps from time to time. Even the big cranefly can settle and rise again from the. surface of the water. This harmless insect is often mistaken for an overgrown mosquito.. A few of these guest stars come and go, but the long, thin water striders are the constant performers, They walk, stride, skate and even stand and wash themselves on the skin of the water.
Yes, the water has a skin. If you are very, very careful, you can make a small sewing needle float on the surface of .n bowl of water ‑ high and dry. That solid, metal needle is light enough to stay on the filmy, fragile: skin of the water. This water skin is called surface tension. Water and oil, as you know, are not friendly and dislike mixing with one another. The skin of the water tends to bend ever so slightly away from an oily or greasy surface. This makes little dimples on the; water, though usually too small for our eyes to see.
The strider and his water‑walking friends make use of these two little: water secrets ‑ the fragile surface skin and the denting away from oil and grease. The graceful bodies of these small insects are light enough to
stand on the skin of the water without piercing it. In fact, it is the floor of their ballet stage, all smooth and bright. These insects also wear special ballet shoes for dancing on the water. Their shoes are furry boots, slick with waxy grease. As he cleans himself, standing so serenely on the water, the strider is carefully coating his fur ballet shoes with waxy brilliantine. He knows that the water will dimple away from his specialfootwear and will not even wet his tiny feet.
The strider’s thin body is supported on six legs like stiff threads, However, the middle pair of legs are used for rowing and you do not often see them. If your eye is at water level, you may see the reflection of the strider's body in the mirror surface of the water. If the sun is shining, you may see his shadow on the pond. His shadowed feet seem to be enlarged far out of proportion. But the shadows include the shadows of the dents in the water skin on which he stands.
The frail surface tension, or water skin, is somewhat elastic. As it stretches, or dents, it becomes taut and wants to spring back again to its original shape. This creates a little push upwards against the strider's feet and adds to his support. He is so safe there that it is hard .for him to pierce the water skin and fall in. But this sometimes does happen, especially when he wants to escape an enemy, When it does, he crawls out, wet and miserable. He dries himself on the bank of the pond before he goes back to his water ballet.