Presence of earthworm species within and beneath Lumbricus terrestris (L.) middens

Speculation exists as to the function(s) of the Lumbricus terrestris midden, but collection of organic matter, inorganic objects and maintenance through cast addition/incorporation suggests that it plays an essential role in the life cycle of this species. Middens act as a focus for soil micro-fauna and encourage microbial activity. This study examines use of L. terrestris middens by earthworms, other than the burrow resident. Middens and associated samples were collected from a woodland site examined over a full year. Sampling involved removal of the intact midden (sample A), and a soil core immediately beneath the midden (sample B). A control core (sample C) was collected within 15 cm of sample B. Mass and sexual condition of the resident L. terrestris, was also examined, where possible. Midden and core samples were hand-sorted for the presence of earthworms in the laboratory, mature individuals were preserved in formaldehyde and identified, whereas immature animals were grown to maturity for identification. In late autumn, winter and early spring significantly (p < 0.05) more earthworms were associated with soil below middens than control samples. Ten earthworm species were found associated within and directly beneath middens. Epigeic and endogeic species were both well represented within the midden itself and endogeic species, such as Aporrectodea caliginosa, dominated in the soil beneath the midden. Juvenile L. terrestris were found within and beneath middens during spring sampling. L. terrestris middens may therefore influence earthworm distribution on a micro-scale.