Description of new species of Stenaelurillus Simon, 1886 from the Western Ghats of India with the redescription of Stenaelurillus lesserti Reimoser, 1934 and notes on mating plug in the genus (Arachnida, Araneae, Salticidae)

Abstract A new species of the jumping spider genus Stenaelurillus Simon, 1886, Stenaelurillus albus sp. n., is described from the Western Ghats of India, one of the biodiversity hotspots of the world. Detailed morphological descriptions, diagnostic features and illustrations of copulatory organs of both sexes are given. Detailed redescription, diagnosis and illustration of Stenaelurillus lesserti Reimoser, 1934 are provided. The occurrence of a mating plug in the genus is reported.


Introduction
The salticid spider genus Stenaelurillus, which is considered a senior synonym of Philotheroides Strand, 1934(Prószyński 1984, was erected by Simon in 1886 to accommodate three species: S. nigricaudus Simon, 1886 (from Senegal), S. nigritarsus Simon, 1886 (from Algeria), which later became a junior synonym of S. nigricaudus (Szűts & Scharff, 2005) and S. triguttatus Simon, 1886 (from Tibet). Wesolowska (2014) reviewed the Asian species of the genus and synonymised S. hainanensis Peng, 1995with S. minutus Song & Chai, 1991 and considered S. setosus Thorell, 1895 as a nomen nudum. Presently the genus has 27 valid species, mostly from Africa (21 species) with only two representatives from India, S. lesserti Reimoser, 1934 (known from both sexes) and S. sarojinae Caleb & Mathai, 2014 (known only from female) (World Spider Catalog 2014). The current paper provides the description of a new species of the genus Stenaelurillus from the Western Ghats, one of the biodiversity hotspots of the world (Myers et al. 2000), in the Kerala region of southern India with the redescription of S. lesserti Reimoser, 1934.

Material and methods
The specimens were preserved in 70% ethanol and studied under a Zeiss Stemi 2000-C stereomicroscope. All measurements are in millimetres (mm) and were made with an ocular micrometer. Length of palp and leg segments are given as: total (femur, patella, tibia, metatarsus (except palp), tarsus). Spine positions are as follows: prolateral, dorsal, retrolateral and ventral. Comparison of the new Stenaelurillus species with all other described species is based only on available literature. Drawings were made by the aid of a drawing tube attached to the microscope. Field photos were taken with Canon EOS 6D with Canon Macro photo lens MP-E65 mm 1:2.8 lens attached. The microphotographic images were taken by Leica DFC295 digital camera attached to Leica M205 C stereomicroscope with the software package Leica Application Suite (LAS), version 4.3.0. All specimens are deposited in a reference collection housed at the Division of Arachnology, Department of Zoology, Sacred Heart College, Thevara, Cochin, Kerala, India (ADSH).

Salticidae Blackwall, 1841 Aelurillinae Simon, 1901
Stenaelurillus Simon, 1886 Diagnosis. Medium sized spiders. Prosoma of all the known Stenaelurillus species has two white transverse stripes. Both male and female have strong bristles on the ocular area. Male palp with a short, not coiled and visible embolus, and tegulum with characteristic retrobasal process. RTA is simple and strongly sclerotized. Epigyne is simple, with thick-walled copulatory openings and short copulatory ducts, and is often accompanied by accessory glands (Szűts and Scharff 2005 Logunov, 2008 as both possess wide copulatory openings (Logunov 2008, Fig. 4 and herein Figs 3A, 9E), but can be distinguished by the presence of small and 'vase'-shaped spermathecae (Figs 3B, 9F) and copulatory ducts with weakly sclerotized anterior part (Fig. 3B).
Description. MALE (holotype, Figs 1A, 8A-F): Prosoma black with white lateral bands of nearly uniform thickness; thoracic region dorsally with paired white longitudinal bands extending back from the rear eyes. Eye field black; anterior row of eyes encircled by black hairs. Clypeus densely covered with white hairs, which is a continuation with that on the lateral margins of carapace. Chelicerae short, vertical, brownish with a thick mid-dorsal transverse layer of white hairs; promargin with two, one large and one small, and retromargin with one large teeth. Fangs short, pale brown. Maxillae, labium and sternum yellowish-brown. Opisthosoma oval; dorsum uniformly shiny black without any pattern; lateral opisthosoma and venter dull yellow with several broken black striations and spots. Trochanters III and IV and coxae III and IV yellowish-brown; trochanters I and II and coxae I and II black; all tarsi brown; all other leg segments dull yellow with broad black patches giving a blackish appearance to the legs. Body length 5.89. Prosoma length 2.98, width (at the middle) 2.08, height (at the middle) 1.72. Opisthosoma length 2.91, width (at the middle) 1.98, height (at the middle) 1.45. Eye diameter: AME 0.44. ALE 0.22. PME 0.06. PLE 0.23. Eye interdistance: AME-AME 0.04. PME-PME 1.35. PLE-PLE 1.33. AME-ALE 0.06. ALE-PLE 0.41. ALE-PME 0.27. PME-PLE 0.14.  (  dorsal and prolateral ones are prominent; patella and tibia disto-dorsally with a long black hair; patella ventro-laterally covered with short yellowish-white hairs; cymbium dark and dorsally with a few long black hairs. Bulb brown; anterior edge of the bulbus has two creamy-white regions, the distal one runs retrolaterally to near the anterolateral edge of the ventral tibial apophysis (Fig. 2E, arrows); retro-basal process of tegulum not fused with the tibia; embolus short with blunt end and is prolaterally directed (  FEMALE (Paratype, Figs 1B, 9A-D): Prosoma black with dull yellow lateral bands, the thoracic part of which is broader; thoracic region dorsally with paired white longitudinal bands extending back from the rear eyes. Eye field black; anterior row of eyes encircled with dull yellow hairs. Clypeus black; Chelicerae short, vertical and dull yellow; promargin with two, one large and one small, and retromargin with one large teeth. Maxillae, labium and sternum yellowish-brown. Opisthosoma widely oval; dorsum black with several dull yellow patches, the posterior three are prominent, which together forming an inverted triangle; lateral opisthosoma and venter dull yellow with several broken black striations and spots. Leg segments dull yellow with black patches and narrow transverse stripes. Palpal segments yellow with black patches; patella, tibia and tarsus dorsally with long black hairs. Body length 6.82. Prosoma length 2.99, width (at the middle) 2.29, height (at the middle) 1.94. Opisthosoma length 3.83,  width (at the middle) 2.84, height (at the middle) 2.27. Eye diameter: AME 0.53. ALE 0.24. PME 0.06. PLE 0.21. Eye interdistance: AME-AME 0.05. PME-PME and nearly half the size of the spermathecae. Anterior part of copulatory duct near the copulatory opening is weakly sclerotized (Fig. 3B).
Etymology. The specific epithet is an adjective and is derived from the whitish part of the tegulum: Latin Albus = white. Gender musculine.
Habitat. Rocky area covered with litter in a deciduous forest (Fig. 12A). Distribution. At present known only from the type locality.   Reimoser, 1934 can be separated from all other described congeners by a transverse fringe of very thin, hard projections resembling hairs at the anterior edge of the harder shield covering the bulbus (Figs 5D-G, 10H-J); females by the presence of unusually enlarged and kidney-shaped spermathecae and the relative position of the copulatory openings (Figs 6A-B, 11E-F).
FEMALE (Figs 4B, 11A-D): Prosoma black, thoracic part with broad yellowishwhite lateral bands; thoracic region dorsally with paired white longitudinal bands extending back from the rear eyes. Eye field black; anterior row of eyes encircled by pale yellow hairs. Clypeus black. Chelicerae short and black; promargin with two, one large and one small, and retromargin with one large teeth. Fangs short, black. Maxillae and labium black. Opisthosoma widely oval; dorsum black with an anterior broad transverse white band and posterior three white spots, which together forming an inverted triangle; lateral opisthosoma pale yellow with several broken longitudinal black striations while venter pale yellow without any striations or spots. Sternum and coxae pale yellow; coxa I retrolaterally black; all other leg segments pale yellow with black patches and narrow transverse black stripes. Palp: posterior 1/4 th of femur black; rest of femur and other segments pale yellow. Body length 6.46. Prosoma length 2.97, width (at the middle) 1.86, height (at the middle) 1.49. Opisthosoma length 3.49, width (at the middle) 2.69, height (at the middle) 1.90. Eyes diameter: AME 0.41. ALE 0.22. PME 0.04. PLE 0.15. Eye interdistance: AME-AME 0.02. PME-PME 1.31. PLE-PLE 1.14. AME-ALE 0.05. ALE-PLE 0.38. ALE-PME 0.21. PME-PLE 0. 16 (Fig. 6A) and placed near the posterior margin of the epigyne (Figs 6A, 11E). Spermathecae are much enlarged and kidney shaped (Figs 6B, 11F).
Habitat. Rocky area having patches of grass and herbaceous vegetation in a semievergreen forest (Fig. 12B).
Distribution. India, Sri Lanka (Wesolowska 2014). Distribution in India. Kerala (new record) and Tamilnadu (Reimoser 1934). Note. Mating plugs, which are supposed to function as paternity protection devices (Uhl et al. 2010;Herberstein et al. 2012), are not very unusual in the animal kingdom and their presence have been described in a number of spider families including Salticidae. Mating plugs are reported in a total of 10 genera and 17 species of salticid spiders (Uhl et al. 2010). Mating plug was observed in the copulatory opening of the two Stenaelurillus species described in this paper. The left copulatory opening of both S. albus sp. n. and S. lesserti were found to be sealed with amorphous secretions (whether male or female origin is unclear) (Figs 7A-B, arrows). Compared to S. lesserti, the mating plug of S. albus sp. n. is more prominent and covering nearly the whole area of the left copulatory opening and the surrounding epigynal region.