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Friday, July 19, 2002

ANIMAL TRACKER

Backswimmer


* Japanese name: Matsumomushi
* Scientific name: Notonecta triguttata
* Description:Backswimmers are aquatic insects, true bugs, with piercing mouthparts. They live underwater and are shaped like small boats, with a keel and a pair of oars -- long, powerful hind legs fringed with hairs -- that propel the insect through the water. Large compound eyes are used to search for prey, and the bug's colors camouflage it from both prey and predators. Because these bugs swim upside down, the black-and-white dorsal side of the backswimmer (that is, its back) faces the bottom of the pond. To potential predators or prey looking up, backswimmers appear to blend in with the light on the surface of the pond. The underside of the bug is muddy brown, so anything looking down might mistake it for the bottom of the pond. Backswimmers are 11.5-14 mm long. They have wings and are good fliers.
* Where to find them: All over Japan, from April to October, in ponds and lakes. The best chance of seeing them is when they come to the surface.
* Food: Backswimmers are among the most aggressively carnivorous of all bugs. They will attack tadpoles, small fish, insects and other arthropods (and fingers, too) and stab them with their sharp beaks. Digestive enzymes are injected into the prey and nutritious fluids sucked out.
* Special features: Backswimmers don't have gills -- they breathe air trapped in fringed pockets on their abdomens. They can adjust their depth by releasing air but have to come to the surface frequently to refill. Since they breathe air from the surface, they can tolerate living in polluted ponds with little oxygen. Backswimmers swim upside down, but they orient themselves by light, not gravity. If they are kept in a tank that is lit only from below, the bugs will swim on their fronts.



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