Cheiracanthium melanostomum ( Thorell, 1895 )

Esyunin, Sergei L. & Zamani, Alireza, 2020, ‘ Conundrum of esoterica’: on the long-forgotten genus Eutittha Thorell, 1878, with new taxonomic considerations in Cheiracanthium C. L. Koch, 1839 (Araneae: Cheiracanthiidae), Journal of Natural History (J. Nat. Hist.) 54 (19 - 20), pp. 1293-1323 : 1305-1307

Cheiracanthium melanostomum ( Thorell, 1895)

Eutittha melanostoma Thorell, 1895, p. 44 (description of ♂ ♀ syntypes from MYANMAR: 70 miles north of Eaugoon , Thayarwaddy; E. W. Oates leg. 1884–1887).

Chiracanthium melanostoma (Sic!): Simon 1901, p. 67; Gravely 1931, p. 264: fig. 17C–D (♂ ♀); Tikader and Biswas 1981, p. 71, figs 123–124 (♀); Biswas and Raychaudhuri 2003, p. 116, figs 1–7 (♂ ♀).

Cheiracanthium melanostoma (Sic!): Majumder & Tikader 1991, p. 62, figs 117–112 (♂ ♀).

Cheiracanthium melanostomum: Deeleman-Reinhold 2001, p. 231 , p. 254, figs 280–281 (♀); Sen et al. 2015, p. 74, figs 414–418, pl. 18 (♀); Dhali et al. 2017, p. 51, figs 185–189, pl. 20 (♀; after Sen et al. 2015).

Chiracanthium (Sic!) melanostomum: Okuma et al. 1993, p. 57 , figs 50, 51A (♂, possibly misidentified).

Comments

This species was originally described from Myanmar (= Burma) ( Thorell 1895). The types of this species were requested, but unfortunately, to date, we have not received any responses from the responsible curator. After comparing specimens from India and Myanmar, Gravely (1931) attributed them under the same name – C. melanostomum . Later, this species was repeatedly redescribed and illustrated with materials from various regions of India ( Tikader and Biswas 1981; Majumder and Tikader 1991; Sen et al. 2015).

The only existing illustrations of the copulatory organ of the female lectotype of C. melanostomum (deposited in the Natural History Museum, London) in Deeleman- Reinhold (2001) are much too small and not detailed enough to give a clear definition of this species. The male paralectotype has never been illustrated. It is not certain if the males that were illustrated by subsequent authors are indeed conspecific with the male paralectotype of this species. Re-examination of the types is urgently necessary for the unambiguous understanding of this species.

Deeleman-Reinhold (2001) included C. melanostomum into a separate species group of Cheiracanthium that is distinct from the punctorium species group. She included three species in this group: Cheiracanthium adjacensoides Song, Chen & Hou, 1990 (as C. insulanum in the text), C. melanostomum and C. brevicalcaratum ( Deeleman-Reinhold 2001, p. 227) , but did not provide a formal diagnosis. We generally agree with Deeleman- Reinhold’s point of view, and establish a melanostomum species group of Cheiracanthium , to which the following four species can be attributed with confidence: C. adjacensoides Song, Chen & Hou, 1990 , C. iranicum sp. n., C. melanostomum ( Thorell, 1895) and C. sadanai Tikader, 1976 . Based on our subjective analysis, the following Cheiracanthium species should also be included in melanostomum species group. All of these species are described from areas within the ranges of C. adjacensoides or C. melanostomum and are very similar to them, but the formal transfer procedure shall be conducted when type (or topotype) material is examined:

– C. danieli Tikader, 1975 (♀ holotype from Mumbai, ♂ allotype from Pune, India)

– C. inornatum O. Pickard-Cambridge, 1874 (♂ and 5 ♀ syntypes from Mumbai, India)

– C. itakeum Barrion & Litsinger, 1995 (♂ holotype and 3 ♂ paratypes from Mindanao Island, Philippines)

– C. mertoni Strand, 1911 (♂ holotype from Aru Island, Indonesia)

– C. taprobanense Strand, 1907 (♂ holotype from Sri Lanka)

– C. vorax O. Pickard-Cambridge, 1874 (♂ and 5 ♀ syntypes from Mumbai, India).

We agree with Wunderlich (2012) that melanostomum species group is closely related to the inclusum species group of Cheiracanthium (for which Chiracanthops Mello-Leitão, 1942 would have to be removed from the synonymy of Cheiracanthium and used, if the inclusum species group was elevated to genus rank, as already proposed by; Wunderlich (2012) and discussed by; Bayer (2014)): Che. inclusum ( Hentz, 1847) , Che. aculeatum Simon, 1884 , Che. africanum Lessert, 1921 , Che. angolense Lotz, 2007b, Che. chayuense Li & Zhang, 2019, Che. furculatum Karsch, 1879 , Che. ilicis Morano & Bonal, 2016, Che. madagascarense Lotz, 2014, Che. schenkeli Caporiacco, 1949 , Che. shilabira Lotz, 2015, Che. subinsulanum Li & Zhang, 2019. Both groups are similar to each other in some characters of the male palp and female epigyne: (1) cymbium with clearly laterally expanded convex cymbial fold; (2) relatively short and stout cymbial spur which is neither covering more than distal third of palpal tibia nor extending beyond palpal tibia in lateral view; (3) embolic base in retrolateral position; (4) long embolus forming an incomplete circle; (5) lamellar TA; (6) tibia with PTA and RTA (DTA absent); (7) epigyne with transverse oval depression (atrium) in the middle;(8) curved CD,which is divided into two parts by a more or less pronounced widening (as reported by Dondale and Redner 1982; Hu et al. 2019), or with ‘two pairs of receptacula seminis’ as reported by Wunderlich (2012); (9) CD not encircling the spermathecae; (10) copulatory openings widely separated from each other, located at the edge of atrium laterally or anterior-laterally; (11) oval or spherical final chambers of spermathecae located posteriorly to the atrium. Species of the melanostomum species group differ from the representatives of the inclusum group in the following characters: unmodified TA rounded at the apex (vs. TA shaped like a wide plate, bilobed at the apex), and epigynal fovea with an indistinguishable anterior margin (vs. anterior margin distinct).

Species of the melanostomum species group are also close to members of the mildei species group of Cheiracanthium (that includes at least four species: C. mildei L. Koch, 1864 , C. kakamega Lotz, 2015 , C. molle L. Koch, 1875 , C. punctipedellum ; Caporiacco, 1949), which is diagnosed by a set of characters similar to those described above. Species of the mildei group differ from members of the melanostomum species group by the presence of an apicodorsal tibial apophysis and the ventrally concave RTA of the male palp, and a ‘flat epigynal plate with a transverse furrow’ ( Dondale and Redner 1982, p. 21). It is very likely that these three conspecific species groups ( inclusum , melanostomum and mildei species groups) will be distinguished into a separate genus (namely, Chiracanthops Mello-Leitão, 1942 ) in the future.

Cheiracanthium melanostomum is very similar to C. adjacensoides , but Deeleman- Reinhold (2001, p. 231) notes that ‘the female designated as lectotype [of the C. melanostomum ] is distinct from that of [ C. adjacensoides ; C. insulanum in the text] by the insemination ducts being further apart anteriorly, and by the spermathecae closer together’. Additional arguments about the separation of these species were given by Dankittipakul and Beccaloni (2012, p. 84).

According to Gravely (1931, p. 264), C. melanostomum is ‘the commonest and one of the most widely distributed of the Indian species of the genus’ (see also Majumder and Tikader 1991, p. 65). In addition, it was recorded in Bangladesh ( Biswas and Raychaudhuri 2003). Another record of C. melanostomum for Bangladesh ( Okuma et al. 1993) is doubtful. The authors provided a brief description and illustrated the males. According to this description, the species differs from C. melanostomum by its smaller size (5.0– 5.5 mm, vs. 7 mm in C. melanostomum ) and the shape of the cymbial spur of the male palp, which is thicker and shorter than that of C. melanostomum .

We do not follow Deeleman-Reinhold (2001, p. 231) on the identity of Cheiracanthium sadanai Tikader, 1976 and C. melanostomum (for details, see the comments on C. sadanai ).