Xystodesmid
Guides
Apheloria
cherry millipedes, flat-backed millipedes
Apheloria is a genus of large, chemically defended millipedes in the family Xystodesmidae, distributed across eastern North America. These millipedes are notable for producing hydrogen cyanide and benzaldehyde as defensive secretions, which imparts a characteristic cherry or almond odor. The genus participates in Müllerian mimicry rings in the Appalachian Mountains, with species displaying highly variable aposematic coloration involving black backgrounds with contrasting yellow, orange, red, or white markings. Species-level identification requires examination of male gonopod morphology due to extensive color polymorphism and convergent color patterns among co-occurring species.
Apheloria virginiensis
Virginia cherry millipede, black-and-gold flat millipede, yellow and black flat millipede
Apheloria virginiensis is a large flat-backed millipede in the family Xystodesmidae, notable as the first myriapod described from North America in 1770. Adults range from 27–59 mm in length and exhibit striking aposematic coloration, typically black with yellow, pink, or orange spots on the paranota. This species secretes hydrogen cyanide and benzaldehyde as a chemical defense, producing a characteristic cherry or almond odor. It inhabits mesic deciduous and mixed forests in the piedmont and coastal plain regions of Virginia and North Carolina, where it contributes to leaf litter decomposition.
Boraria stricta
Boraria stricta is a flat-backed millipede in the family Xystodesmidae, characterized by its dorsoventrally flattened body form typical of the order Polydesmida. The species is native to North America and belongs to a genus known for aposematic coloration warning of chemical defenses. Like other xystodesmid millipedes, it possesses paranota—lateral extensions of body segments that contribute to its flattened appearance.
Cherokia georgiana georgiana
Cherokia georgiana georgiana is a millipede subspecies in the family Xystodesmidae, characterized by its black body with yellow wedge-shaped posterolateral markings and a wrinkled dorsal surface. It belongs to the order Polydesmida, a group distinguished by lateral expansions of dorsal segments into "paranota" that give a flattened appearance. Like other members of its genus and related genera, it produces hydrogen cyanide (HCN) as a chemical defense against predators, with its bright coloration serving as aposematic warning signals.
Chonaphini
Chonaphini is a tribe of flat-backed millipedes (Polydesmida) within the family Xystodesmidae, established by Verhoeff in 1941. The tribe comprises approximately 6 genera and 19 described species distributed across western North America. Members exhibit the characteristic dorsoventrally flattened body form typical of xystodesmid millipedes.
Dicellarius lamprus
Dicellarius lamprus is a species of flat-backed millipede in the family Xystodesmidae. It was described by Chamberlin in 1918 and is found in North America. The species belongs to a genus of xystodesmid millipedes characterized by their flattened body form.
Euryurus erythropygos
Euryurus erythropygos is a North American millipede species in the family Xystodesmidae, first described by Brandt in 1839. It belongs to a genus characterized by broad, flattened bodies and distinctive coloration patterns. The species name 'erythropygos' refers to its red or reddish posterior (pygidium). Like other xystodesmid millipedes, it likely produces defensive secretions containing benzoquinones when disturbed.
Euryurus evides
Euryurus evides is a North American millipede species in the family Xystodesmidae, order Polydesmida. It belongs to a genus of flat-backed millipedes characterized by their broad, flattened bodies and distinctive color patterns. The species was described by Bollman in 1887 and is part of the tribe Euryurini within the subfamily Rhysodesminae. It is among the more frequently observed millipedes in its range, with substantial occurrence records on community science platforms.
Pleuroloma cala
Pleuroloma cala is a flat-backed millipede in the family Xystodesmidae, endemic to peninsular Florida south of the Suwannee River. It is one of four recognized species in the genus Pleuroloma, distinguished from the widespread P. flavipes by subtle morphological differences in segmental profile, sternal configuration, and male gonopod structure. The species was originally described as Zinaria cala by Chamberlin in 1939.
Rhysodesmus
Rhysodesmus is a genus of flat-backed millipedes in the family Xystodesmidae, established by Cook in 1895. The genus contains at least 90 described species, with Rhysodesmus dasypus serving as the type species and recognized as the largest known xystodesmid millipede. Species in this genus range from El Salvador northward through Mexico to the southern United States. The genus is taxonomically significant within the Polydesmida order but remains incompletely characterized for many species.
Semionellus
Semionellus is a genus of flat-backed millipedes in the family Xystodesmidae, established by Chamberlin in 1920. The genus contains at least three described species: S. michiganus, S. placidus, and S. tertius. Members are found in the north-central and northeastern United States, including Michigan, Indiana, Ohio, Minnesota, and Maryland. As xystodesmid millipedes, they share the characteristic flattened body form typical of this diverse family of polydesmidan millipedes.
Sigmocheirini
Sigmocheirini is a tribe of flat-backed millipedes (Order Polydesmida) in the family Xystodesmidae, established by Causey in 1955. The tribe contains the genus Sigmocheir, whose species are endemic to California's Sierra Nevada foothills. Members of this tribe exhibit the characteristic flattened body form typical of xystodesmid millipedes.
Sigmoria australis
Sigmoria australis is a flat-backed millipede in the family Xystodesmidae, described by Shelley in 1986. It belongs to the order Polydesmida, a group characterized by their dorsoventrally flattened bodies and distinct lateral extensions (paranota) on each segment. The species is known from North America, with confirmed records from Florida.
Sigmoria bidens
Sigmoria bidens is a species of flat-backed millipede in the family Xystodesmidae, described by Causey in 1942. It belongs to the order Polydesmida, one of the largest orders of millipedes, characterized by their flattened bodies and keeled tergites. The genus Sigmoria is part of the tribe Apheloriini within the subfamily Rhysodesminae. Very few observations of this species have been documented, with only 8 records in iNaturalist as of the knowledge cutoff.
Sigmoria latior
Red-sided Flat Millipede
Sigmoria latior is a flat-backed millipede in the family Xystodesmidae, commonly known as the Red-sided Flat Millipede. The species was described by Brölemann in 1900 and is native to North America. Four subspecies are recognized, including the nominate subspecies S. l. latior and S. l. hoffmani, S. l. mariona, and S. l. munda. As a member of the tribe Apheloriini, it belongs to a group of xystodesmid millipedes known for their often striking coloration.
Sigmoria nantahalae
Nantahala Cherry Millipede
Sigmoria nantahalae is a species of flat-backed millipede in the family Xystodesmidae, first described by Hoffman in 1958. It is endemic to the southern Appalachian Mountains of North America, with confirmed records from North Carolina. The species belongs to the tribe Apheloriini, a group known for producing hydrogen cyanide as a defensive secretion.
Sigmoria plancus
Sigmoria plancus is a species of flat-backed millipede in the family Xystodesmidae, first described by Loomis in 1944. It belongs to a genus of eastern North American polydesmid millipedes characterized by distinctive color patterns and defensive chemical secretions. The species is part of a taxonomically complex group where species boundaries and distributions remain incompletely documented.