How are earthworms classified based on their activity?

Explanation

1. Earthworms are divided into two major groups.
2. The first group, the humus formers, dwell on the surface and feed on organic matter. They are generally darker in colour.
These worms are used for vermicomposting.
3. The second group, the humus feeders, are burrowing worms that are useful in making the soil porous, and mixing and distributing humus through out the soil.