Background: The existing descriptions of the woodlouse Trachelipusvespertilio are based on a single female collected in Croatia in the nineteenth century. No further information on the occurrence of this species has been reported in published literature and the morphology of the male, which may offer additional reliable diagnostic characters, has remained unknown.
New information: On the basis of new material collected in Slovenia, a description of the male morphology of T.vespertilio is provided along with a species diagnosis. The rediscovery of this woodlouse after more than a century extends its distribution range to Slovenia.
Keywords: Slovenia; crustacean; soil fauna; terrestrial isopods; woodlice.
Miloš Vittori.