The flat-backed millipede is a species of Polydesmid millipede native to Western Europe. The flat-backed millipede is a rather small species of millipede, typically reaching 24 millimeters (0.94 inches) in length, in captivity, however, individuals can reach 50 millimeters (2 inches) or as small as 18 millimeters (0.71 inches), this great amount of variety has been attributed to the quality of nutrition and humidity. They are quite similar to other species in the same genus, only being distinguished by the shape of a male's gonopods or female epigyne. As the name suggests, the flat-backed millipede is a rather flat millipede, with all 20 segments' chitin extending laterally, an adaptation for digging and camouflaging in leaf litter. is most frequently found throughout Western Europe, encompassing the British Isles; with occasional sightings in both the Eastern and Western reaches of the United States and the southern expanse of Canada, presumably as an invasive species.