Organism of the Day
|August 01, 2012||Yellow Buckeye / Aesculus flava|
|July 27, 2012||Eastern Hay-Scented vs. New York Fern /|
|July 25, 2012||Leaf-footed Bug Nymph / Acanthocephala terminalis|
|July 23, 2012||Timber Rattlesnake / Crotalus horridus|
|July 20, 2012||Smooth Chanterelle / Cantharellus lateritius|
|July 19, 2012||Black Rat Snake / Pantherophis obsoletus|
Water Scorpion, Ranatra sp.
June 29, 2012
Water scorpions—at first glance, swimming twigs with four legs and a cruel set of pincers—in fact belong to the order Hemiptera, or true bugs. Despite their vicious appearance, they are not capable of harming anything larger than a mayfly nymph. However, the stick-insect disguise and the violent ambush of their prey surely make this slow-moving insect a true terror in the aquatic invertebrate community.
Water scorpions have thin, elongate brown bodies 30-35 mm long, with a tail that adds an additional 10-15 mm to their length. Their front two legs have been modified to grasp prey, working on a “jack-knifing” design to fold in and pin their prey close to their mandibles. The thin, spindly, rear four legs work together to propel the insect forward when it is threatened using oar-like, jerky movements. Unlike the tail of a real scorpion, the tail of species in the genus Ranatra is not dangerous. It is merely a pair of straight, flexible siphons, jointed only at the base, that serves (in a simplistic sense) as a snorkel. Water scorpions, being air-breathing insects, carry a bubble of air with them between their forewings and their abdomen. When the tip of the long tail breaks the surface, diffusion via the tail between the bubble and the surrounding air renews the water scorpion’s oxygen supply. However, oxygen also dissolves into the bubble from the surrounding water. Thus, in highly oxygenated water with many plants close to the surface, the water scorpion will hardly ever have to surface for air. In the winter, water scorpions are able to survive in this way, even when trapped underneath ice, because the low temperatures dampen their metabolism to the point where the oxygen that dissolves into their air bubble is sufficient for survival.