The species composition and number of micromycetes and the activity of enzymes (protease, urease, polyphenol oxidase, and peroxidase) in coprolites and excreta of earthworms (L terrestris, A. caliginosa, and E. fetida) are described. It is supposed that the contribution of earthworms to the formation of soil humic acids depends on the ability of particular species to decompose organic matter (mineralization capacity) and induce polyphenol oxidase activity.