Apheloria montana

Distinguished from congeners by gonopod morphology. The junction between acropodite and prefemur features a distinct tubercle in A. montana versus an acute angle in A. polychroma. The acropodite is smoothly circular in A. montana but has a distinct elbow-like bend in A. virginiensis. The bright yellow or orange aposematic coloration combined with black dorsal surface separates it from non-aposematic polydesmid millipedes in the same region.

Adults measure 42–55 mm in length and weigh approximately one gram. The dorsal surface is predominantly black with yellow legs. Yellow spots appear on the paranota (lateral extensions of body segments) and along the midline of the back—one spot on the collum and one on each metazonite. A color variant in Little Switzerland, North Carolina, displays smaller orange spots and orange legs instead of yellow. Females are generally larger than males. Adults possess 20 body segments (counting collum as first and telson as last). Adult females have 31 pairs of legs; adult males have 30 leg pairs, with leg pair 8 modified into gonopods. The gonopod acropodite (distal portion) is uniformly narrow and curved into a circular shape; the prefemur (proximal portion) bears a scythe-shaped projection.

Inhabits mesic deciduous forests, typically found under decaying leaf litter on the forest floor. Also occurs in less moist habitats including mixed forests and rhododendron groves. Documented in association with pine, maple, oak, beech, tulip poplar, witch hazel, alder, sweetgum, and buckeye.

Endemic to the southern Appalachian Mountains. In Tennessee: Cocke, Greene, Unicoi, and Washington counties. In North Carolina: Buncombe, Madison, McDowell, and Mitchell counties.

Feeds on leaf litter. Relies on coprophagy (consumption of fecal pellets) for survival; individuals deprived of feces in laboratory conditions became inactive and ceased feces production after 21 days, with some losing weight or dying within one week. Does not appear to rely on internal symbionts for cellulose digestion; instead utilizes bacterial activity in fecal pellets.

Produces hydrogen cyanide and benzaldehyde as chemical defense against predation. These compounds are released when the millipede is disturbed and produce a characteristic cherry or almond odor. The bright coloration serves as aposematic (warning) signaling to predators.

Functions as a detritivore in forest ecosystems, processing leaf litter. Coprophagic behavior suggests role in nutrient cycling through microbial processing of fecal material. The species' chemical defenses and aposematic coloration represent a documented case of defensive mutualism with co-occurring toxic millipedes in related genera (Pleuroloma, Boraria, Cherokia), where shared warning signals may enhance predator learning.

• Apheloria polychromaOverlaps in eastern Tennessee; distinguished by acute angle (not tubercle) at acropodite-prefemur junction
• Apheloria virginiensisOccurs in North Carolina; distinguished by elbow-bent (not smoothly circular) acropodite
• Pleuroloma flavipesSimilar black-and-yellow aposematic coloration and flat-backed morphology in the same family; distinguished by genus-level gonopod characteristics and geographic separation

• millipede
• polydesmida
• xystodesmidae
• aposematic coloration
• chemical defense
• hydrogen cyanide
• detritivore
• coprophagy
• appalachian endemic

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