Abstract
Twelve species of the genus Achaearanea belonging to the family Theridiidae are recorded from Japan. A key and illustrations of the species are given. A new species, A. ryukyu, is described. A. simulans (Thorell 1875) is recorded from Japan for the first time. A. ungilensis Kim & Kim 1996 described from Korea is synonymized with A. japonica (Bösenberg & Strand 1906).
