The role of the burrow structure in the characterisation of trap door spiders Nemesia Audouin, 1826 (Araneae, Mygalomorphae)

Three new species of the trap-door spider genus Nemesia Audouin, 1826 are described from southern Portugal, namely Nemesia bonali sp. nov. from Portimão and Alvor, Nemesia molerobaltanasi sp. nov. from Castelão (Loulé), and Nemesia rebellis sp. nov. from Odeleite. These species have specific morphological and/or behavioural similarities with N. athiasi Franganillo, 1920, N. fagei Frade & Bacelar, 1931, and N. ungoliant Decae, Cardoso & Selden, 2007, but are easily distinguishable if attention is paid to all details including the size, the prosoma shape and the burrow structure. The available literature on N. fagei is discussed and the need to consider the burrow as a possible character for diagnosis when describing and identifying species of the genus Nemesia is illustrated. Finally, a few guidelines are proposed to aid in the study of these spiders, both at the species level and for the general understanding of spiders of this genus.