Abstract
A new medium-sized species of Cybaeus (Araneae: Cybaeidae) from the westernmost part of Honshu, Japan, is described under the name C. akiensis. The species most resembles C. kuramotoi Yaginuma 1963, which is sympatrically found with C. akiensis n. sp., and C. ashikitaensis (Komatsu 1968) inhabiting Kyushu. Local species assemblage of the genus Cybaeus in western Honshu consists of 5 to 6 species with different body sizes. Cybaeus akiensis n. sp. is the second largest species in the five-species assemblage found in the distributional range of the species. Collecting records revealed that the species overwinters as both adults and juveniles and two years are needed from hatching to maturity. Silken retreat of the species bears two terminal openings and a loophole at the bottom, the latter is a feature only rarely found among Japanese species of Cybaeus.
