Apheloria

Species-level identification requires examination of male gonopod morphology. The acropodite is circular (O-shaped) in most species, but ρ-shaped in A. whiteheadi. The prefemur bears a scythe-shaped projection in most species, but this is short and broad in A. whiteheadi. Color pattern alone is unreliable for species identification due to extensive intraspecific variation and Müllerian mimicry with co-occurring species of Brachoria and other xystodesmid genera. Distinguished from the closely related genus Rudiloria by acropodite shape: oval (0-shaped) in Rudiloria versus circular in most Apheloria. Distinguished from other flat-backed millipedes by the combination of large size, chemical defense, and specific gonopod morphology.

Large millipedes ranging from 40–60 mm in length. Body distinctly flattened with lateral expansions of dorsal segments (paranota), giving a flat-backed appearance typical of the order Polydesmida. Adults possess 20 body segments (counting collum as first and telson as last); adult females have 31 pairs of legs, adult males have 30 pairs (excluding leg pair 8, modified as gonopods). Coloration highly variable: black background with aposematic markings in yellow, orange, red, or white, arranged as either longitudinal stripes or 2–4 spots per tergite. Paranota often feature red spots or red tinge on inner margin. Gonopods distinctive at genus level: acropodite (distal part) uniformly narrow and curved into circular (O-shaped) form in most species; prefemur (proximal part) with scythe-shaped projection. Apheloria whiteheadi deviates with ρ-shaped acropodite and short, broad prefemur projection.

Deciduous forest floors in temperate broadleaf forests. Found in mull soil formation environments where leaf litter decomposition occurs. Occupies forest floor microhabitats with accumulated organic matter.

Eastern North America from southern Quebec, Canada south to northern South Carolina and southeastern Oklahoma; west to eastern Oklahoma and southern Wisconsin. Disjunct populations west of the Mississippi River in the Ozark and Ouachita Mountains. Specific records include: southern Quebec, southern Ontario, New England west to Connecticut River, New York, Pennsylvania, Appalachian Mountains, Ohio Valley, Great Lakes region (southern Michigan, southern Wisconsin), mid-Atlantic states to western shore of Chesapeake Bay, southeastern states to Bald Head Island (North Carolina), northern South Carolina, Alabama to Tennessee River, Arkansas, and eastern Oklahoma.

Leaf litter; specifically documented as a mull-forming millipede that processes decomposing plant material to create mull soil.

Development through typical diplopod stages: egg, immature with progressive segment and leg pair addition, adult. Adults with 20 segments (including collum and telson). Sexual dimorphism in adult leg number: females 31 pairs, males 30 pairs (leg pair 8 modified as gonopods). Specific details of egg deposition, juvenile development rates, and longevity not documented in available sources.

Chemical defense: produces hydrogen cyanide (HCN) and benzaldehyde through ozopores when disturbed. The benzaldehyde imparts a characteristic cherry or almond odor, giving rise to the common name 'cherry millipedes.' Defensive secretion effective against predators due to cytochrome c oxidase inhibition. Slow, deliberate locomotion typical of large polydesmid millipedes. Flight response not documented; relies primarily on chemical defense rather than escape behavior.

Decomposer and soil engineer. Contributes to mull soil formation through processing of leaf litter, enhancing decomposition and nutrient cycling in forest ecosystems. Model species in Müllerian mimicry rings in the Appalachian Mountains, where color patterns serve as honest signals of chemical defense to predators. Co-occurs with other chemically defended xystodesmid millipedes (including Brachoria species) in these mimicry rings, with convergent coloration reinforcing predator learning.

Ecologically beneficial as decomposers in forest ecosystems. Chemical defense secretion contains hydrogen cyanide and can be irritating; handling may cause skin discoloration or mild irritation in sensitive individuals. The distinctive cherry/almond odor of defensive secretions is notable but not of commercial significance. Not documented as agricultural pest or beneficial species in managed systems.

• BrachoriaCo-occurs in Appalachian Mountains and participates in Müllerian mimicry rings with Apheloria; species closely mimic color patterns of Apheloria species, making visual identification challenging. Distinguished by gonopod morphology and phylogenetic placement.
• RudiloriaClosest relative within tribe Apheloriini; shares gonopod features including flange on basal part of acropodite. Distinguished by acropodite shape: oval (0-shaped) in Rudiloria versus circular (O-shaped) in most Apheloria species.
• PleurolomaRelated genus in family Xystodesmidae with similar aposematic yellow and black coloration and chemical defense with HCN. Distinguished by gonopod morphology and distribution; Pleuroloma flavipes occurs further west and has distinct gonopod structure.

• millipede
• diplopod
• polydesmid
• xystodesmid
• chemical defense
• cyanide
• benzaldehyde
• aposematic coloration
• Müllerian mimicry
• decomposer
• forest floor
• eastern North America
• Appalachian Mountains
• Ozark Mountains
• Ouachita Mountains
• gonopod morphology
• mull-forming

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• 2019 Arkansas/Oklahoma Insect Collecting Trip iReport | Beetles In The Bush
• predator avoidance | Beetles In The Bush | Page 5
• Biology of a Mull-Forming Millipede, Apheloria coriacea (Koch)
• Apheloria polychroma, a new species of millipede from the Cumberland Mountains (Polydesmida: Xystodesmidae)
• Noteworthy Geographic Distributional Record for the Milliped, Apheloria virginiensis reducta (Polydesmida: Xystodesmidae), from the Arkansas Delta
• DISTRIBUTION OF THE MILLIPED GENUS APHELORIA CHAMBERLIN, 1921; SUMMARIES OF PERIPHERAL LOCALITIES AND ONES OF A. VIRGINIENSIS (DRURY, 1770) WEST OF THE MISSISSIPPI RIVER (POLYDESMIDA: XYSTODESMIDAE)