ABSTRACT
Spiders are one of the most common groups inhabiting subterranean environments. They are predators, and are usually abundant inside caves, from the entrance to the deepest galleries. Not all species occurring in caves are exclusive to the subterranean environment: around 25-30% are accidentals (trogloxenes) and appear in or around the entrance zone; around 50% of the species are regularly found in caves but also occur in the epigean environment (troglophiles); and between 20-25% are strictly cavernicolous (troglobitic). These troglobitic species are the most interesting from a taxonomical and evolutionary perspective since they are, in many cases, the living representatives of ancient evolutionary lineages that are now extinct in the epigean environment.
