Flat-backed Millipedes

Order Polydesmida

The Flat-backed Millipedes (Order Polydesmida) includes 81 species across 9 families and 44 genera in our directory.

About Flat-backed Millipedes

Polydesmida (flat-backed millipedes) is the largest millipede order with ~3,500 described species. Many species produce hydrogen cyanide (HCN) as a chemical defense - a strategy unique among arthropods.

Economic Impact

Millipedes are generally beneficial decomposers but can occasionally damage seedlings and soft fruits in gardens. Some tropical species cause skin irritation through their cyanide-based defensive secretions.

Ecological Role

Flat-backed millipedes are major leaf litter decomposers in forest ecosystems, recycling calcium, nitrogen, and other nutrients. Their fecal pellets contribute significantly to soil formation and humus production.

Families in Polydesmida (9)

Species in Polydesmida (81)

Apheloria tigana

Xystodesmidae

A. tigana is the dominant xystodesmid in central NC, particularly the "Triangle" (Raleigh‒Durham‒Chapel Hill). Individuals typically have yellow paranota, a yellow middorsal spot on the anterior margin of the collum or 1st segment, and yellow middors

Cherokia georgiana

Xystodesmidae

Identification: Male gonopods Fluoresces under UV light

Granulated Millipede

Scytonotus granulatus

Polydesmidae

Identification: dorsum with low rounded tubercles/pustules; in females, paranota slightly smaller on segments 6‒7; males have one pair of legs on segment 6, females have two

Harpaphe haydeniana

Xystodesmidae

Identification: see secretes a dark fluid that has an odor similar to the almond extract

Howellaria deturkiana

Xystodesmidae

Identification: Paranota red-orange with caudal metatergal line connecting them. Anterior portion of metazonites mottled brown-black. Collum similar. Antennae, legs white. Gonopods with an "apically prolonged acropodite." Also have "ventrally spined

Howellaria infesta

Xystodesmidae

Identification: Paranota red-orange, dorsum brown-black. Collum similar. Legs white, antennae dirty yellow.

Nannaria terricola

Xystodesmidae

Identification: Greenish black to olive gray, lateral lamina, legs and under side of body dirty white. Anal scutum triangular, very acute behind; ten long hairs on anal valves two-thirds to three-fourths the length of the anal scutum. Feet slender, p

Orthomorpha coarctata

Paradoxosomatidae

Identification: Body dark brown to black in adults. Mid-body paranota (segments 8-9) are sharp posteriorly, extending beyond segment margin. Male gonopod on 7th segment long and slender, reaching posterior legs of 5th segment.

Pseudopolydesmus canadensis

Polydesmidae

Identification: Most of paranota a deep, brick-red color, with the rest of the dorsum being a dark black. Slightly smaller than Ps. serratus . Gonopods Often sympatric with other congeners

Pseudopolydesmus paludicolus

Polydesmidae

Identification: A very small Pseudopolydesmus with two rows of quadrate areas on tergites. Paranota more noticeably directed caudally than in other species. A dark burgundy species, easily blends in with leaf litter

Selenocheir arcuata

Xystodesmidae

Identification: Acropodite of the gonopod blade-like and forming a broad, poorly defined arc without distinct distal curvature. Cuadrolateral corners of the paranota angular on segments 2-3, blunted on 4-8 and distinctly rounded on remaining tergites

Semionellus placidus

Xystodesmidae

Identification: Paranota reduced, peach-colored and connected by a caudal peach metatergal band. Prozonite and anterior metazonite brown. Legs, antennae white. Gonopods: prefemoral process expanded into a corkscrew-like shape, acropodite whip-like. F