These millipedes have a mostly Holarctic distribution that extends south not only to Mexico and North Africa but also as far as Java.

Colors range from pitch black through reddish or brownish to pallid and are rarely vivid.

The collum is small, in the shape of a transverse oval, with a smooth anterior margin.

The paranota are simple but usually well developed and dentate laterally.

[2] This family includes species notable for featuring sexual dimorphism in segment number: Adult females in the genus Perapolydesmus have the usual 20 segments (counting the collum as the first segment and the telson as the last), but the adult males have only 19.