Psechrus libelti Kulczynski 1908
Creators: name: Bayer, Steffen
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Psechridae
Psechrus
Psechrus libelti

description: Psechrus libelti Kulczyński, 1908
Figs 2 C–D
Psechrus libeltii Kulczyński 1908: 561, pl. 23, fig. 31 (Description and illustration of ♀). Levi 1982: 125 (Synonymy with P. singaporensis Thorell, 1894).
Psechrus argentatus— Simon 1901: 47, misidentified.
Psechrus libelti— Bonnet 1958: 3804 (Emendation). Bayer 2012: 21 (Removed from synonymy with P. singaporensis, description and illustration of ♂ and ♀).
Psechrus singaporensis— Levi 1982: 125, figs 40–53, ad part, figs 42–43, 48–53 misidentified (figs 48–51: illustration of ♀). Jocque and Dippenaar-Schoeman 2006: 219, figs 86a–f (Illustration of ♂ and ♀, misidentified).
Material examined. MALAYSIA: Peninsula Malaysia: Pahang: Krau Game Reserve, Bukit Rengit, ca. 03°37'N, 102°10'E, 400–500 m, primary forest, H.S. Yong leg. 10.II.2013, s.a. ♀ (SB 1272), SMF 64103.
Comparative material of Psechrus argentatus (Doleschall, 1857). INDONESIA: Maluku Prov.: Ambon island (‘Amboina’), Prof. Cel. O. Beccari leg. 1872–1877, T. Thorell det. 1877, 1 s.a. ♀ (SB 593), MNHN AR192/ 1–2. Ambon island, unknown leg. 1959, ex Museum Buitenzorg 14.09.1960, 1 s.a. ♀ (SB 1287, only opisthosoma remaining), SMF 64582.
Remarks. In previous studies subadult females of this species were not available, so with the present subadult female it is possible to characterise the pre-epigyne and pre-vulva of P. libelti for the first time.
Primordial copulatory organ. The pre-epigyne is characterised by the relatively flat pre-median septum, exhibiting a few small and fine ridges (Fig. 2 C). The pre-lateral lobes do not run parallel with the body’s longitudinal axis, but antero-medially in a 45° angle to that axis (Fig. 2 C). The pre-vulva is recognisable underneath the cuticle as a profile on each side antero-laterally of the anterior parts of the lateral lobes. A preepigynal field is hardly recognisable. The pre-muscle sigilla are longer than broad, of irregular shape and are clearly further separated from the pre-septum than from each other (Fig. 2 C). In the pre-vulva the medially located and rounded pre-copulatory ducts are the most characteristic features, because they are at least twice as large as the pre-spermathecae (incl. pre-spermathecal head) (Fig. 2 D). The pre-spermathecal heads still lack the long stalks that are present in and typical for the spermathecal heads of adult females of the argentatus -group. In comparison to pre-vulvae of other Psechrus species, the pre-spermathecae are located far anteriorly and hence are easy recognisable. In general all the characters described above apply to the pre-epigyne and pre-vulva of Psechrus argentatus (Doleschall, 1857) as well (Figs 2 A–B and Bayer 2012, figs 4d–e). However, in P. argentatus the pre septum is minimally shorter than in P. libelti. Moreover, the distance between the pre-septum and the pre-muscle sigilla is longer in P. argentatus (Fig. 2 A). It remains to be seen if the shorter distance in the P. libelti specimen (Fig. 2 C) is indeed representative for all subadults of that species. Herewith, for now the ratio “distance between pre-septum and pre-muscle sigilla divided by the width of pre-septum” is> 2 in P. argentatus and <2 in P. libelti. The pre-vulvae of these two species are indistinguishable.
Taxonomic remarks. Even though the specimen was recorded as the only one from that locality (without adult material), there are no doubts that it belongs to Psechrus libelti: I have examined much material of the argentatus - group and to date I have recognised only two, very similar species. Both are remarkably widely distributed. All specimens recorded from Sumatra, Southern Thailand, Malaysia and Borneo have been identified as P. libelti and those recorded from Flores, Sulawesi, Moluccas, New Guinea, New Britain etc. identified as P. argentatus. The possibility that this specimen belongs to an undescribed species of the argentatus -group is unlikely because its preepigyne is extremely similar to that of P. argentatus (see above). P. libelti is also very similar to P. argentatus with regard to the copulatory organs of adult females (Bayer 2012). Like the pre-vulvae of the subadults, the vulvae of adults are indistinguishable. Therefore P. libelti and P. argentatus can be considered sibling species. Moreover, I know of nearby records of adult female P. libelti specimens, e.g. from the Templers Park and from Kampung Belimbing.
The differences between the adult epigynes of P. libelti and P. argentatus (the former with longer septum, lateral septum margins without notches and epigynal field slightly shorter) are not completely expressed in the respective pre-epigynes. Exceptions are the pre-median septum, which is minimally longer in P. libelti and the distance between pre-septum and pre-muscle sigilla, which is shorter in P. libelti (a long and distinct epigynal field connecting the septum with the muscle sigilla like present in adult females does not exist in subadults of both species). The other diagnostic differences concerning the shape of the median septum as visible in mature female epigynes apparently develop completely within the developmental step between the subadult and the adult instars. In other similar species pairs of Psechrus (e.g. P. marsyandi Levi, 1982 and P. himalayanus Simon, 1906) differences of diagnostic characters of the adult female copulatory organs are more clearly expressed in the primordial female copulatory organs (Bayer 2012). Even though subadult females of P. argentatus and P. l i be l t i are extremely similar and difficult to distinguish, a determination according to geographic information might be successful as these two species are allopatric.
Distribution. (Southern) Thailand, Malaysia, Brunei, Indonesia (Sumatra, Borneo).
description: Published as part of Bayer, Steffen, 2014, Seven new species of Psechrus and additional taxonomic contributions to the knowledge of the spider family Psechridae (Araneae), pp. 1-54 in Zootaxa 3826 (1) on pages 9-10, DOI: 10.11646/zootaxa.3826.1.1, http://zenodo.org/record/286429