Syllophopsis peetersi

Specimens of this species were collected by Winkler sampling carried out at Silent Valley National Park, a primary tropical rainforest in Kerala. Located in the Nilgiri hills of Western Ghats of India, the park represents one of the last undisturbed tracts of tropical moist evergreen forest in India. The region has a mean annual rainfall of 6,066 mm and a mean annual temperature of 20.2C. The litter samples were taken from thick leaf litter and moisture laden soil near tree trunks, from two sites along the banks of the river Kunthi (Kunthipuzha). One site was in the buffer zone (Mukkali) and one in the core region (Sairandhri). The Sairandhri region forms the gateway of Silent Valley. The type locality of this species is known for its ancient history and relict ant taxa (Bharti & Akbar 2013a, b, c, 2015; Dad et al. 2019).

The majority of the species in the genus have been collected via Winkler sampling, inhabiting leaf litter from the tropical rainforests (AntWeb 2021), and same holds true for Syllophopsis peetersi. The species appears rare, with a restricted distribution. However, it is quite possible that the species occurs elsewhere in southern India and Sri Lanka, in areas with similar habitat.

Identification
This species is distinct from all congeners in having striate mandibles, a character shared with members of the closely related genus Trichomyrmex. It is quite similar in appearance to members of the radiation in Madagascar, but not to the species that occur elsewhere. The Syllophopsis that occur outside of Madagascar are more-or-less uniform in appearance. They are all characterized by a single faceted eye (more than five ommatidia in S. peetersi), a relatively narrower head and closely approximated frontal lobes (frontal lobes well-separated in S. peetersi). Most of the bulkier and larger-eyed species in Madagascar have ventral rugae on the petiolar peduncle, but these are lacking in S. peetersi. It is somewhat similar to Syllophopsis hildebrandti. The two species can be differentiated based on following characters. In S. peetersi the eyes consist of more than five ommatidia, there is dense body pilosity, the metanotal groove is strongly impressed and in profile view the promesonotum is higher than the propodeum. In contrast, S. hildebrandti has eyes consisting of a single ommatidium, the body pilosity is less distinct, the metanotal groove is indistinct and, in profile, the promesonotum forms a continuous arch that includes and is not raised above the propodeum. Syllophopsis sechellensis differs from S. peetersi in smaller eyes, and the entire mesopleuron is matte and reticulate punctate. Likewise, Syllophopsis australica, reported from Sri Lanka, has reduced eyes and closely approximated antennal insertions.

Distribution based on Regional Taxon Lists
Oriental Region: India.

Nomenclature

 * . Syllophosis peetersi Akbar et al., 2021: 405, figs. 1–6 (w) INDIA.

Type Material

 * Holotype worker: India, Kerala, Silent Valley National Park, 11.0939N, 76.4462E, Kerala, India, 900 m.a.s.l., 25.ix.2011, Winkler extraction method, leg. S.A. Akbar (unique specimen identifier PUAC5001).
 * Paratypes: 6 workers with same data as holotype (PUAC5002–PUAC5007).

Description
Worker

Head longer than wide (CI 83–85); vertex planar to slightly concave; frons shining and smooth with sparse piliferous pits and a few striolae around antennal sockets; frons with incurved and semierect setae (Figs 2a, 3a–b). Eye distinct, well developed, consisting of more than 9 ommatidia, eye width 1–2× greatest width of antennal scape, eyes set about midpoint of head capsule, more-or-less circular with curvature of inner eye margin slightly more pronounced than that of its outer margin, ommatidia of compound eyes are loosely and regular deployed having few curved sensilla in-between (Figs 3c–d). The frontal lobes are well-separated and the anteromedian seta is situated well under a protrusive ledge (Fig 3e). Clypeal carinae weakly defined with anteromedian clypeal margin narrowly convex between weakly ridged clypeal carinae; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin ending slightly anterior to antennal fossae. Mandibles with 4–5 teeth and one denticle (on second basal tooth); mandibles linear-triangular with few piliferous pits and distinctly striate; masticatory margin of mandibles strongly oblique (Figs 3f–g); anterior tentorial pit is situated far away from the antennal sockets (Fig 3h). The torulus appears as circular sclerites with a well marked torular lobe; placed within is antennal bulbus having series of sensilla trichodea (Figs 3i–m). Antennae consist of 12 segments with a 3-segmented distinct club; scape, pedicel and flagellum are well separable (Fig 4a). Compared with the rest of the antennal segments, the scape consists of fewer but longer pilosity (Figs 4b–c). Pedicel and rest of the antennal segments mainly consist of curved sensilla trichodea, with some of them having grooved surfaces (Figs 4d–i). The apical antennal segments which form the club also have few sensilla trichodea curvata (tc) along lateral sides (Figs 4j–k). Most of the sensilla are concentrated along the apical flagellomere (Fig 4l). The terminal flagellomere has a dense covering of sensilla trichodea curvata (tc), few sensilla basiconica (b) and some sensilla trichodea (t) (Figs 4m–p). Most of the basiconica and sensilla trichodea appear paired (Fig 4o). On the tip of terminal flagellomere there are also few small pores in the cuticle representing the openings of the sensilla ampullacea (a) and sensilla coeloconica (c) (Figs 4p–q). The very tip of the flagellomere is characterised by very granulated or porous surface (Fig 4r). The general surface of head consists of regularly placed sensilla trichodea throughout with gena mostly devoid of any distinct pilosity (Figs 4s–t). The sensilla are strongly curved at the base and their sockets are quite tight (Fig. 4u). Head cuticle is more or less ribbed (Figs 4v–w). Pilosity near tentorial pits consists of short curved hairs (Fig 4x).

Mesosomal outline in profile broadly convex and smoothly rounded, promesonotum slightly raised compared to propodeum (Figs 2b–c, 5a–b). Metanotal groove strongly impressed, with distinct transverse costulae (Figs 5c–d). Mesosoma shining and smooth with faintly striolate mesopleuron posteriad. Promesonotal setae a mixture of incurved, semierect setae, slightly shorter decumbent setae, and sparse appressed setulae. Propodeum with dorsum longer than the posterior (declivitous) face; mostly smooth and shining with dorsum having few weak striolae; propodeum with erect to decumbent setae along dorsum and entire declivitous face; propodeal spiracle nearer to declivitous face of propodeum than metanotal groove; vestibule of propodeal spiracle distinct; propodeal lobes present as rounded flanges, metapleural gland with a distinct circular opening (Figs 5e–g). Petiolar node cuboidal, shining and smooth throughout without any ventral rugae on the petiolar peduncle; petiolar spiracle situated anteriad of petiolar node (Fig 5h); postpetiole shining and smooth; postpetiolar sternite depressed, anterior carina inconspicuous (Fig 5i). Four distinct gastral tergites with sharp pointed sting; the terminal gastral segment has a circular stigma opening (Figs 5j–m); gastral tergites, with a mixture of incurved, semierect setae and slightly shorter decumbent setae.

The legs with strongly swollen femur and a stout tibia, calcar, basitarsus, five tarsomeres and sharply pointed claws (Fig 6a). The surface of leg shows presence of scattered sensilla trichodea (t). The protibial spur of forelegs (calcar of strigil) appears distinct with grooved squamiform and spatulate setae (Figs 6b–j). Claws with long setae and arolium between the pointed claws in all the legs (Figs 6k–m). The tarsomeres also have a dense covering of long sensilla trichodea (Figs 6n–o).

Color yellowish to very light brown.

Measurements (n=11; range with holotype in brackets): EL 0.11–0.13 (0.11), HL 0.68–0.73 (0.71), HW 0.58–0.61 (0.60), SL 0.50–0.52 (0.51), ML 0.65–0.77 (0.74), PRW 0.51–0.53 (0.52), PL 0.25–0.27 (0.26), PPL 0.22–0.24 (0.23), PPW 0.24–0.26 (0.25), PW 0.25–0.28 (0.27), PH 0.28–0.29 (0.29), PPH 0.25–0.26 (0.26) mm.

Indices: CI 83–85 (84), SI 82–86 (85).

Etymology

The species epithet honours the late Professor Christian Peeters and is a masculine genitive noun. The name ‘Peeters’ is derived from the Greek root word Petrus (‘rock’ or ‘stone’) which also appropriately symbolises the foundational stature of Prof. Christian Peeters’ work in the study of ants.