Lumbricidae s.l. (earthworms) belong to the saprophagous soil fauna. Worldwide ca. 6000 species are known. In Europe there are about 670 species, most of them lumbricids; ca. 30 of them occur in Germany. Abundances and biomass vary considerably, depending on site conditions and management practices. From the very beginning of soil biology, earthworms have been considered to be the most important soil animals in many sites in Central Europe. Reasons for this are not only their high biomass but also the important functions they perform in the soil ecosystem: mechanical mixing of soil fractions, acceleration of decomposition of dead organic material, or amelioration of the water holding capacity by formation of clay-humus complexes.
It should be noted that these functions, generally considered to be positive, are usually performed by only a few species. Earthworms can be classified into three major ecological groups: mineral soil dwellers (endogeics), litter layer dwellers (epigeics), and vertical burrowers (anecics); the best-known species among the latter is Lumbricus terrestris. Referring to species occurring in Europe, a large body of autecological and ecotoxicological data is available. Their distribution is well-known in forest sites, but information on grassland and arable-field sites is deficient.
Concepts exist for assessing the ranges of reference values for biomass and species numbers under different site conditions. All domestic species can be identified with standard identification literature. To collect earthworms, a combination of hand sorting and chemical expulsion is considered the standard method. Collecting and identifying earthworms is uncomplicated. The animals are easy to conserve and can be identified without further preparation