Worms, Pacific Northwest
The Dew Worm is found in great numbers all along the coast of the Pacific Northwest. They are a common species of earthworm that is active at night but will also come to the surface during wet or rainy weather and crawl about. They will often leave casts on the surface which make lawns bumpy and uneven. Dew worms are more common on older, shaded or heavily watered lawns.
Dew worms are extremely valuable in creating topsoil and maintaining soil fertility. Earthworm castings, or excrement, are richer in minerals than the soil which the earthworm has swallowed. The earthworm constructs its burrow by forcing its front end through crevices and swallowing soil. The eaten soil and mucus mixture is removed from the burrow as castings. During dry seasons or during the winter, earthworms migrate to deeper levels of the soil.
Earthworms are scavengers and feed on the dead organic matter at the surface of the soil and may pull leaves into their burrows. They will also feed on organic matter obtained from the soil that is swallowed during their burrowing.
They are most common in moist soil rich in organic matter, or with at least a layer of hummus or thatch on the surface. Young worms and small species are usually found in the top few inches of the soil, while others will have a wider distribution but are still limited to the upper level of the soil that contains some organic matter. The tunnels of larger species range from the surface to several meters in depth, depending on the soil.