Flat-backed
Guides
Boraria
Boraria is a genus of flat-backed millipedes in the family Xystodesmidae, established by Chamberlin in 1943. The genus is characterized by the lateral expansion of dorsal segments into paranota, giving individuals a flattened appearance distinct from cylindrical millipedes. Species in this genus, like other xystodesmids, produce hydrogen cyanide as a chemical defense and display bright aposematic coloration—typically black with yellow or orange markings—as warning signals to predators. The genus is part of the diverse Polydesmida order, which represents the culmination of diplosegmentation in millipedes with no external evidence of sutures between fused body somites.
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.
Polydesmidae
flat-backed millipedes, tractor millipedes
Polydesmidae is a family of millipedes in the order Polydesmida comprising over 240 species across more than 30 genera. These millipedes are characterized by their flattened, plate-like dorsal exoskeletons that give them the common name "flat-backed millipedes." They range from 4 mm to 30 mm in length and display coloration from black through brownish to pallid, rarely vivid. The family has a predominantly Holarctic distribution extending to Mexico, North Africa, and Java, with highest diversity in the Mediterranean region. Several species exhibit notable biological traits, including sexual dimorphism in segment number and chemical defense secretions.
Xystodesmini
Xystodesmini is a tribe of flat-backed millipedes within the family Xystodesmidae, order Polydesmida. The tribe was established by Hoffman in 1978 and contains multiple genera of medium to large-sized millipedes found primarily in North America. Members are characterized by their flattened bodies with lateral extensions (paranota) and often display aposematic coloration. The tribe is well-represented in citizen science observations, with over 18,000 records on iNaturalist.