Two new species in the tube-web spider genus Ariadna Audouin, 1826 (Segestriidae Simon, 1893) are described from South Australia based on morphological features of both males and females. Ariadna clavata sp. n. and Ariadna tangara sp. n. are widespread and sympatric on eastern Kangaroo Island, where they are found beneath bark, in borer holes in dead wood, and in short burrows under rocks. They have also been found in south-eastern mainland South Australia and bring the total number of described Australian Ariadna to 13 species. We showcase intraspecific variation in both species based on a significant number of specimens, including substantial size variation in females and variations in patterns of leg spination. For male Ariadna, we also establish the previously unknown functions of apophyses and spines on the metatarsi and tibiae on the first legs, which are used during mating to clasp the female.