Earthworms are not native to Minnesota. If they ever were, they did not survive the last period of glaciation that ended 11,700 years ago. We do not know if they ever occurred in Minnesota because, having neither an internal skeleton nor an exoskeleton, their bodies do not fossilize. There are at least fifteen species of earthworms found in Minnesota. All of them were imported from Europe and Asia.
Nightcrawler (Lumbricus terrestris) is a common, large earthworm. It is native to western Europe but is now widely distributed throughout the temperate and mildly boreal regions of the world. It is considered invasive outside of its native range, including in Minnesota. Its spread is attributed to human activities, including the movement of soil as ship’s ballast, importation of exotic plants, and disposal of fish bait. It is not the most abundant earthworm in Minnesota but it is the most often encountered.
Nightcrawler is identified by the large size, up to 8″ long; the stout body, often as thick as a pencil; the broad, flattened posterior; the well-developed “saddle”; and the color, dark in front and light behind the saddle.