WHIRLIGIG BEETLES
Almost everyone has seen whirligig beetles swimming around in circles on the surface of the water. They are small, bronze or black beetles, and seem to be continuously in motion. Their eyes are divided, so that there is a lower half and an upper half, perhaps to see objects both above and below the water's surface. They can apparently see well enough above the surface, as you will find if you try to capture one with your dip-net.
A whirligig larva is small and may easily be overlooked in a collection of fresh-water animals. It has fringed gills along the sides of its abdomen, and four hooks at the end of its body with which it can anchor the tip of its abdomen to a stick or plant stem.
Like the young diving beetle, the whirligig larva sucks juices from the bodies of animals upon which he feeds. An adult whirligig beetle is also carnivorous. In winter, whirligigs hibernate in mud. Like most
other water beetles, the adults live a long time.
WATER PENNIES
If you live near a creek or river, you may have found "water pennies" on the under sides of rocks you have lifted out of the water. Each of these flattened, copper-colored animals is the larva of a water beetle. If you put a beetle larva from a pond into a swiftly flowing river, it would be carried away, but the water penny is so flat that it clings fast to a rock or other object.
There are six legs and five pairs of gills on the under side of a water penny's body. When it is grown, this particular insect is called a riffle beetle. Its hairy body is about one-fourth inch long.
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