Driloleirus macelfreshi

Oregon giant earthworm

Family: Megascolecidae · Class: Oligochaeta · Order: Haplotaxida

The Oregon giant earthworm (Driloleirus macelfreshi) is one of North America's largest earthworm species, reaching up to 1.32 meters (4.3 feet) in length with a diameter between 0.5 and 1 centimeter. This pale whitish annelid is distinguished by its characteristic large size and distinctive floral, lily-like odor when handled, giving rise to the genus name Driloleirus meaning "lily-like worm" (Xerces Society 2019). The clitellum, a reproductive structure located toward the head of the worm, extends from segments 13 to approximately 22. The Oregon giant earthworm has an extremely limited distribution, known from only 15 sites in Oregon's Willamette Valley and one site in the Oregon Coast Range. Documented occurrences include Lincoln, Linn, Marion, Polk, Yamhill, and Benton counties, with potential habitat in Lane County where it has not yet been confirmed but is expected to occur (Xerces Society 2019). This species belongs to the family Megascolecidae within the order Haplotaxida. Like other indigenous Oregon earthworms, this species exhibits a narrow range of tolerance for soil conditions, favoring fine-textured soils rich in clay content. The worm is generally associated with deep, undisturbed soils in moist mixed forests dominated by Douglas firs, grand firs, and bigleaf maples. These specific habitat requirements reflect the species' adaptation to the unique soil chemistry and forest structure of the Pacific Northwest. Limited information exists regarding the specific behavior and ecological role of the Oregon giant earthworm. As with other large earthworm species, it likely plays a significant role in soil aeration and nutrient cycling within its forest ecosystem. The species' large size suggests it may have different feeding patterns and soil movement capabilities compared to smaller earthworm species, though detailed ecological studies are lacking. The Oregon giant earthworm faces significant conservation challenges and is classified as critically imperiled with a NatureServe global status of G1 and is listed as vulnerable on the IUCN Red List (Xerces Society 2019). It is designated as a Bureau Sensitive Species by the Bureau of Land Management. The two primary threats identified are habitat loss due to widespread conversion of Willamette Valley lands for agriculture, industry, and urban development, and competition from introduced earthworm species. The species' narrow habitat requirements and limited distribution make it particularly vulnerable to environmental changes. A major challenge in conservation efforts is the lack of effective survey protocols for detecting this elusive species. The Oregon giant earthworm's secretive nature and specific habitat requirements make population monitoring difficult, preventing accurate assessment of current population status and trends. Conservation recommendations include developing improved detection methods, conducting comprehensive surveys to evaluate current distribution and abundance, and training biologists in species identification protocols. Additionally, educating landowners and managers about the species' conservation needs is essential for protecting remaining populations in both the Willamette Valley and Oregon Coast Range.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.