A Revision of Taiwanese Species in the Genus Psammoecus Latreille (Coleoptera, Silvanidae).

Takahiro Yoshida, Michael Karner, and Toshiya Hirowatari (2018) This study revises the taxonomy of Taiwanese species in the genus Psammoecus Latreille, 1829. A new species, P. taiwanensis sp. nov., is described, and six species from Taiwan are recoded for the first time: P. harmandi, Grouvelle, 1912, P. dentatus Grouvelle, 1883, P. trimaculatus Motschulsky, 1858, P. triguttatus Reitter, 1874, P. labyrinthicus Yoshida and Hirowatari, 2014 and P. hiranoi Yoshida and Hirowatari, 2013. The following taxonomic synonyms are proposed: P. delicatus Grouvelle, 1908 = P. x-notatus Grouvelle, 1912 syn. nov. = P. nitidior Grouvelle, 1919 syn. nov. = P. raffrayi Grouvelle, 1919 syn. nov.; P. harmandi, Grouvelle, 1912 = P. boreas Yoshida and Hirowatari, 2014 syn. nov.; P. dentatus Grouvelle, 1883 = P. scitus Yoshida and Hirowatari, 2014 syn. nov.; P. simonis Grouvelle, 1892 = P. stultus Grouvelle, 1912 syn. nov. A key to Taiwanese Psammoecus species, a redescription of P. delicatus, and notes on the variability of P. harmandi are provided.

Jumping kinematics in the wandering spider Cupiennius salei.

Spiders use hemolymph pressure to extend their legs. This mechanism should be challenged when required to rapidly generate forces during jumping, particularly in large spiders. However, effective use of leg muscles could facilitate rapid jumping. To quantify the contributions of different legs and leg joints, we investigated jumping kinematics by high-speed video recording. We observed two different types of jumps following a disturbance: prepared and unprepared jumps. In unprepared jumps, the animals could jump in any direction away from the disturbance. The remarkable directional flexibility was achieved by flexing the legs on the leading side and extending them on the trailing side. This behaviour is only possible for approximately radial-symmetric leg postures, where each leg can fulfil similar functions. In prepared jumps, the spiders showed characteristic leg positioning and the jumps were directed anteriorly. Immediately after a preliminary countermovement in which the centre of mass was moved backwards and downwards, the jump was executed by extending first the fourth and then the second leg pair. This sequence provided effective acceleration to the centre of mass. At least in the fourth legs, the hydraulic and the muscular mechanism seem to interact to generate ground reaction forces.