Tetramorium sinensis sp. nov.

Figs 1, 2

Material examined.

Holotype worker: China • Guangdong Province, Zhongshan City, Fenghuang Mountain Park; 22°29'18"N, 113°18'32"E; elev. 35 m; in D. rugosum nest; 08–November–2021, Huasheng Huang leg.; No. GXNU 2102704; (GXNU: GXNU 2102704). Paratype worker: China • 25 paratype workers from the same colony as the holotype (23 workers, GXNU; 1 worker, SWFU; 1 worker, IZCAS).

Diagnosis.

Head in full-face view subrectangular, slightly longer than broad, long longitudinally striate from the anterior clypeal to the middle of head, lateral and posterior part of head slightly reticulate; eyes small, with 3–4 ommatidia in the greatest diameter. Mesosoma in dorsal view longitudinally sculptured, pronotum front slightly reticulate; in lateral view, distinctly dense transverse sculptured, propodeal spines short triangular and the tip straight. propodeal lobe angular. Petiole in dorsal view circular, as long as broad.

Measurements and indices.

Holotype worker (N = 25): Measurements: HL: 0.59–0.64; HW: 0.54–0.57; SL: 0.36–0.38; PH: 0.30–0.32; PW: 0.38–0.42; ML: 0.68–0.72; ED: 0.05–0.07; PTL: 0.20–0.21; PTH: 0.20–0.21; PTW: 0.19–0.20; PPH: 0.20–0.21; PPL: 0.17–0.19; PPW: 0.23–0.25. Indices: CI: 89.06–91.53; SI: 66.67; OI: 9.26–12.28; DMI: 55.88–58.33; LMI: 44.12–44.44; PeNI: 47.62–50.00; LPeI: 100.00; DpeI: 95.00–95.24; PpNI: 59.52–60.53; LPpI: 85.00–90.48; DPpI: 131.58–135.29; PPI: 121.05–125.00.

Description.

Head. Antennae with 12 segments; antennal scape slightly curved; scape reaching two-thirds of the length of the head. Head in full-face view subrectangular, slightly longer than broad, lateral margins convex, posterior margin slightly concave in middle, with posterolateral corner rounded, frontal carina short, only reaching to the middle of head. Anterior clypeus nearly straight, antennal scrobe obvious (Fig. 1 A); in lateral view, the diameter of the eye less than half of the maximum diameter of the enlarged part of the antennal terminal segment (Fig. 1 D).

Mesosoma. In dorsal view, lateral margins slightly convex, anterior margin convex (Fig. 1 C); in lateral view, dorsal outline strongly convex, with transverse curve; promesonotal suture and metanotal groove inconspicuous; mesopleuron demarcated from pronotum by a distinct suture, but not demarcated from mesonotum and metapleuron; propodeal spines short triangular (Fig. 1 D).

Metasoma. In dorsal view, petiole circular, as long as broad; lateral margins slightly convex; anterior margin convex and posterior margin slightly concave (Fig. 1 C); in lateral view, petiolar node slightly convex dorsal outline, slightly higher than long, with bilateral edge sloped slightly (Fig. 1 D). Postpetiole in dorsal view clearly larger than petiole, oval, lateral margins apparently convex, as long as broad (Fig. 1 C); in lateral view, slightly convex dorsal outline (Fig. 1 D). In dorsal view, anterior margin of gaster obviously concave (Fig. 1 C).

Sculpture. Mandibles and clypeus longitudinally striate; antennal scape finely puncta; frontal area longitudinal striate, lateral and posterior part of head slightly reticulate (Fig. 1 A). The pronotum reticulate, the mesonotum and metanotum longitudinally striate (Fig. 1 C); the lateral sides of the mesosoma with transverse curve and sparsely puncta (Fig. 1 D). Dorsum of petiole sparsely rugose (Fig. 1 C). Coxa, peduncle, subpetiolar process with dense puncta (Fig. 1 D). Gaster smooth and shining (Fig. 1 C).

Pilosity. Body entirely covered with abundant decumbent, sub-erect, and erect hairs (Fig. 1 A, C, D).

Coloration. Body brown. Antennae and legs slightly yellowish-brown (Fig. 1).

Etymology.

The new species name is derived from the Latin word “ Sina ” (sinensis), a reference to the type locality.

Distribution.

China (Guangdong).

Biology.

The new species was collected multiple times from the nests of the queenless ant Diacamma rugosum (Le Guillou, 1842) in the soil of a plantation forest in Fenghuang Mountain Park, Shaxi Town, Zhongshan City, Guangdong Province, China. Consequently, in order to test the relationship between them, a detailed excavation of one of the nests was carried out by Huasheng Huang (Fig. 3 A). Employing a hoe and pick to ascertain the direction of the ant without causing damage to the ant path whenever possible (Fig. 3 C), small tools like tweezers and spoons were then used to trace the ant path (Fig. 3 B). After an intensive 6 - hour excavation, Huasheng Huang discovered both D. rugosum and T. sinensis sp. nov. in the same nest area at a depth of 1.4 m (Fig. 4 B, C). Once the shallow loose soil layer was removed, the main nest of T. sinensis sp. nov. became visible (Fig. 4 A).

Based on observed facts, the two species share an ant canal and inhabit the same nest area; however, T. sinensis sp. nov. builds its own nest and broods its eggs, leading to the hypothesis that T. sinensis sp. nov. may exhibit parabiosis in the nest of D. rugosum. This assumption is primarily supported by the significant body type and population of D. rugosum, which suggests that T. sinensis sp. nov. is unlikely to provide sufficient food for D. rugosum. Therefore, we preliminarily believe that T. sinensis sp. nov. may feed on the food scraps left by D. rugosum and share the foraging trails. However, the method or pathway by which T. sinensis sp. nov. enters the nest of D. rugosum remains unclear, and long-term observation is needed to uncover this mystery.

Recognition.

Tetramorium sinensis sp. nov. bears a resemblance to T. jarawa (Agavekar, Hita Garcia & Economo, 2017) due to the presence of similar longitudinal striae in the frontal area and posterior part of the head slightly reticulate in the full-face view of the head. However, it can be distinguished from the latter by the lateral sides of the mesosoma exhibiting transverse striae (while entirely reticulate punctate in T. jarawa), the propodeal spines short triangular, as long as broad basally and the tip straight (while the propodeal spines are long, significantly longer than broad basally and the tip upturned in T. jarawa). In dorsal view, the petiole of T. sinensis sp. nov. is as long as broad, distinguishing it from T. jarawa where the petiole is longer than broad.