The Worms

There are three different ecological groups of European earthworms and nine different species that have been found in Minnesota, they are identifiable by size and color. Earthworms are known as good detritivores because they consume large amounts of dead material in a very short period of time. Before earthworms invaded, the primary detritivores in hardwood forests were bacteria and fungi. Because they broke down material so slowly a thick, spongy layer of litter developed over time. (UMN 2005)

Epigeic	Anecic	Endogeic

Epigeic worms are reddish in color and as their name suggests, live and feed exclusively in the surface litter of the soil causing limited mixing of mineral and organic soil layers. (Bohlen et al 2004) Their coloration serves to camouflage them and they reach a maximum size of 2 to 7 centimeters. (UMN 2005)

Anecic worms, also known as night crawlers, can get up to 10 to 15 centimeters in size. They are also reddish in color and eat fresh litter at the surface of the soil but also make burrows, sometimes up to 2 meters deep. (UMN 2005) These species incorporate litter into the soil and bring mineral soil from different depths to the survace, resulting in soil mixing that is very different from the mixing caused by epigeic or endogeic species. (Bohlen et al 2004)

Endogeic worms are whitish gray and live and feed only in the soil or under logs. They almost never come to the surface and therefore do not require camouflaging pigment. When they feed on leaves or other organic material, the soil (ie excrement) they leave behind are called casts. (UMN 2005) This species reside in the mineral or mixed soil layers and often enhance mixing of organic and mineral soil layers. (Bohlen et al 2004)

Not all species fall neatly into these standard categories, but these classificiations are useful for differentiating major ecological groups and their effects. (Bohlen et al 2004)

Interesting facts: In a study published in Ecological Applications, the epi-endogeic species Lumbricus rubellus led to the most rapid removal of forest floor material during initial invasion. Epigeic and epi-endogeic species of earthworms may facilitate the establishment of other species of earthworms leading to the establishment of stable populations of endogeic and anecic species, which prevent recovery of the forest floor. (Hale and Frelich 2005)

View pictures of epigeic, anecic and endogeic worms