Walking on Water
Pond skaters appear to be resting in the still surface of pond water but are always at the ready. Suitable prey might chance to wander by, and if so, the predators will pounce. Pond skaters are so quick on their feet as they skim the surface of the water that these carnivores can easily catch an unwary insect. It had only come to the pond for a drink but lost its life to the skaters.
The bodies of pond skaters are covered with silver water-repellent hairs that prevent them being damp. They frequently jump considerable distance but never break water’s surface. Their hind legs steer them along the stream of water very freely and smoothly. Pond skaters are so confident and stable on the surface of the water that they can even mate there easily. Sea-skaters, meanwhile, though possibly hundred of miles from the nearest land mass, move on the same way as pond skaters but over the deep ocean surfaces. This insect moves across the water at speeds of up to 30 inches per second.
These insects weigh so little that they can frequently take advantage of the phenomenon of surface tension. Indeed, if they are light enough and can spread their weight, they are able, literally, to walk on water without going through surface. Then, by rowing motions with their legs, they can skate around on the surface at an impressive rate. If they are predatory, any movement on the surface will make ripples travel outward. Then all the pond skaters have to do is pounce on the prey. But if one type of Rove beetle is in the vicinity, however, they may not be so lucky, and a deadly skating competition, with the loser ending up as lunch, might begin. This Rove beetle has a remarkable method of moving. It can secrete a drop of fluid from the tip of its abdomen, and the fluid will lower the surface tension of the water behind it so that it is drawn forward at a rapid rate without much effort. This is a fantastic means of making a speedy get-away to safety or of accelerating in the role of predator.
Thursday, January 8, 2009
Walking on Water