Mesoniscus is restricted to Central Europe and the Balkan Peninsula; the ranges of its two species do not overlap.

[1] In Austria, its range extends from the Karwendel near Innsbruck to the eastern edge of the Wienerwald, although it is also found in isolated pockets of Triassic and Silurian–Devonian limestone in Styria.

[3] The first description of a woodlouse now in the genus Mesoniscus was in 1858, when Camill Heller described "Titanethes alpicolus" in 1858.

[4] This was followed in 1865 by the description by János Frivaldszky (Ján Frivaldský) of the subspecies "Titanethes alpicolus graniger".

[5][6] Mesoniscus species lack the pleopodal lungs found in many other woodlice, and are restricted to damp environments.