We humans may think we rule the world, but the bugs have got us beat. Scientists estimate that there are a million of them for every one of us! Here, roughly grouped, are the earth's most common critters (not counting bacteria, algae and other teensy microbes, which are most numerous of all).

1. Insects and spiders

2. Crustaceans (Animals with hard shells and jointed bodies and legs: crabs and shrimp, for example)

3. Worms

4. Fish

5. Mollusks (Animals with soft, nonsegmented bodies and sometimes a hard shell, such as snails and shellfish)

Source: The Top Ten of Everything by Russell Ash; DK Publishing; 1997

Daily News from TIME for Kids

April 4, 1997 World Report