Euryurus erythropygos

The combination of a broad, flattened polydesmid body form with conspicuous red terminal segments distinguishes this species from most sympatric millipedes. The red pygidium is particularly diagnostic within its range. It may be confused with other Euryurus species, but E. erythropygos can be separated by details of gonopod structure (male reproductive appendages) and the specific pattern of coloration on the posterior body. Close examination of male gonopods is required for definitive identification among congeners.

Adults have a broad, flattened body typical of the Polydesmida order. The species exhibits a dark body with contrasting red or reddish-orange coloration on the terminal segments (pygidium), which gives rise to its specific epithet. The paranota (lateral extensions of body segments) are well-developed and contribute to the flattened profile. Individuals reach moderate size for the family, with adults typically 25–40 mm in length.

Found in moist forested environments, particularly in deciduous woodlands with abundant leaf litter and decaying wood. Occurs under logs, stones, and within the upper layers of soil and humus. Requires humid microhabitats to prevent desiccation.

Eastern North America. Documented from the Appalachian region and surrounding areas, with records from the eastern United States. The precise northern and southern limits of its range require further documentation.

Active during warmer months; surface activity peaks in spring and summer. Likely moves deeper into soil or rotting wood during winter or dry periods. iNaturalist observations span March through November, with most records from April to October.

Detritivore: feeds on decaying leaf litter, decaying wood, and other decomposing plant material.

Development through typical diplopod hemianamorphosis: hatchlings emerge with fewer segments than adults and add segments through molts until reaching the adult complement of 20 body segments (plus telson). Sexual maturity is reached after the final molt. Detailed life history data specific to this species are not documented.

When disturbed, exhibits the typical defensive behavior of xystodesmid millipedes: curls tightly into a spiral to protect the ventral surface, with the red pygidium often exposed outward. This posture may serve as aposematic (warning) coloration advertising chemical defenses. Slow-moving, primarily nocturnal or crepuscular.

Contributes to decomposition and nutrient cycling in forest ecosystems through consumption and fragmentation of plant detritus. Serves as prey for various invertebrate and vertebrate predators. Its defensive secretions may influence soil microarthropod community composition.

Occasionally encountered by hikers and naturalists in eastern forests. The defensive secretions can stain skin and may cause minor irritation if handled; washing hands after contact is recommended. No economic importance.

• Euryurus leachiiOverlapping range and similar body form; distinguished by differences in male gonopod morphology and subtle coloration differences on the pygidium
• Other Xystodesmidae genera (e.g., Pleuroloma, Nannaria)Share flattened body form but lack the distinctive red pygidium; gonopod structure differs substantially
• Apheloria virginiensisSympatric xystodesmid with bright coloration, but has yellow-and-black banding rather than dark body with red posterior

• millipede
• diplopod
• detritivore
• forest
• aposematic
• North America
• xystodesmid

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life