Rotastruma epispina Hosoishi & Yamane, 2021

Hosoishi, Shingo, Yamane, Seiki & Sokh, Heng, 2021, A third species of the rare ant genus Rotastruma (Hymenoptera, Formicidae) from Cambodia, with illustrated generic diagnoses and key to species, Deutsche Entomologische Zeitschrift 68 (2), pp. 225-233 : 225

Rotastruma epispina Hosoishi & Yamane sp. nov.

Figs 1-6 , 7-11 , 12-14 , 15-17

Type material examined.

Holotype: Cambodia • worker; Kampong Thom Province, regrowth forest; 12°38'N, 105°16'E; 24 Dec 2010; S. Hosoishi leg.; colony SH10-Cam-172; KUEC. Paratypes: Cambodia • 3 workers; Kampong Thom Province, regrowth forest; 12°38'N, 105°16'E; 24 Dec 2010; S. Hosoishi leg.; colony SH10-Cam-172; KUEC; 2 dealate queens; Kampong Thom Province, regrowth forest; 12°38'N, 105°16'E; 24 Dec 2010; S. Hosoishi leg.; colony SH10-Cam-172; KUEC.

Non-type material examined.

Cambodia • 2 pale-coloured workers; Kampong Thom Province, regrowth forest; 12°38'N, 105°16'E; 24 Dec 2010; S. Hosoishi leg.; colony SH10-Cam-172; KUEC.

Diagnosis of worker.

Posterior margin of head almost straight. Lateral margin of head slightly convex. Propodeal spine curving upwards. Petiole pedunculate, peduncle longer than high. Two suberect hairs present around posterolateral corner of head.

Measurements

(in mm) and indices of holotype worker. HW 0.62; HL 0.73; MaL 0.37; SL 0.50; EL 0.21; TL 3.32; WL 0.84; PNH 0.30; PNW 0.44; MW 0.31; SPL 0.30; PTL 0.45); PTH 0.22; PTW 0.20; PPL 0.25; PPH 0.23; PPW 0.26; CI 84; SI 81; MaI 61; PI 46); PPI 106.

Measurements (in mm) and indices of paratype worker (n = 3). HW 0.62-0.63; HL 0.75; MaL 0.35-0.37; SL 0.51-0.53; EL 0.20-0.21; TL 3.25-3.40; WL 0.84-0.86; PNH 0.28-0.29; PNW 0.45-0.46; MW 0.30-0.32; SPL 0.28-0.30; PTL 0.44-0.46; PTH 0.22-0.24; PTW 0.20-0.21; PPL 0.23-0.25; PPH 0.22-0.23; PPW 0.27-0.28; CI 82-84; SI 81-86; MaI 57-59; PI 44-46; PPI 110-120.

Description of worker.

Head rectangular in full-face view, longer than broad (CI 82-84), with posterior margin almost straight, lateral margin slightly convex and posterolateral corner rounded. Eye large, in the longest dimension with 11-13 ommatidia. Frontal carina irregularly extending to posterior margin of head. Mandible with 6 teeth; two apical teeth large. Antenna 12-segmented, with 3-segmented club; scape not reaching posterolateral corner of head.

With mesosoma in dorsal view, lateral margins converging posteriad; anterolateal corner of pronotum rounded; mesonotum and propodeum laterally marginate; metanotal groove indistinct. In lateral view, pronotum, mesonotum and anterior propodeum forming a slightly convex dorsal outline. Mesopleuron marginated anteriorly in lower half, demarcated from pronotum and metapleuron. Propodeum with steeply sloping declivity that is laterally marginated with carinae; spine long, directed diagonally upwards, with apical 2/3 slightly down-curved; spiracle very close to apex of metapleural gland bulla.

In dorsal view, petiole rectangular with almost parallel sides. Petiole pedunculate in profile view; peduncle longer than high, dorsally almost continuous to anterior slope of node. Petiolar spiracle located at mid-length of peduncle (measured from anterior extremity of peduncle). Subpetiolar process small and triangular. Postpetiole globular and distinctly wider than petiole in dorsal view, as high as petiolar node in lateral view (PTH 0.22-0.24; PPH 0.22-0.23).

Frons with two to three pairs of longitudinal rugulae; irregular rugulae in several specimens. Dorsum of head between frontal carina and eye reticulate-rugose. Clypeus with median longitudinal rugula and one or two rugulae laterally. Pronotum dorsally reticulate with smooth interspaces, laterally with rugulae running anteroposteriorly. Mesonotum sparse with irregular rugae interrupted by transverse rugulae posteriorly. Mesopleuron, metapleuron and lateral surface of propodeum shiny, with sparse anteroposteriorly running rugulae. Dorsum of propodeum generally smooth, with weak irregular sculpture. Petiole and postpetiole reticulate-rugulose in dorsal and lateral view; dorsum of petiolar peduncle, anterior slope of petiolar node and petiolar sternite only superficially sculptured. First gastral tergite smooth, with short basigastral costulae.

Sparse standing setae present on dorsal surfaces of head, mesosoma, petiole, postpetiole and first gastral tergite; those on gastral sternites shorter. Two standing setae present around posterolateral corner of head. Clypeus bearing a pair of setae medially at anterior margin. Scape and flagellum with suberect setae.

Colour yellowish-brown; first gastral tergite with broad brown band.

Measurements (in mm) and indices of paratype queen (n = 2). HW 0.64-0.68; HL 0.79-0.82; MaL 0.41-0.42; SL 0.53-0.54; EL 0.24-0.25; TL 3.88-4.01; WL 1.05-1.10; PNH 0.30; PNW 0.56; MW 0.59-0.60; SPL 0.35-0.36; PTL 0.54-0.55; PTH 0.26-0.27; PTW 0.25-0.26; PPL 0.25-0.27; PPH 0.25-0.26; PPW 0.32-0.34; CI 81-83; SI 80-83; MaI 62-64; PI 46-49; PPI 126-128.

Description of queen.

Head rectangular in full-face view, longer than broad (CI 81-83), with posterior margin almost straight (slightly concave medially), lateral margin slightly convex and posterolateral corner rounded. Eye large, in the longest dimension with 12-13 ommatidia. Median ocellus at the level with posterior margin of eye. Frontal carinae extending to anterior margin of lateral ocellus and diverging towards posterior margin of head. Mandible with 6 teeth; two apical teeth large. Antenna 12-segmented with 3-segmented club; scape not reaching posterolateral corner of head.

In dorsal view, mesosoma longer than wide, wider anteriorly, gradually narrowed posteriad; pronotum demarcated from mesonotum, with evenly convex anterior margin and weakly convex lateral margin; metanotal groove distinct. In lateral view, dorsum of mesonotum slightly convex. Propodeal spiracle round and close to anterior margin of metapleural gland bulla. Wing scars clearly visible. Propodeal spines directed diagonally upwards, almost straight, apically blunt.

In dorsal view, petiole rectangular with almost parallel lateral margins. In lateral view, petiole pedunculate, with an ill-defined node; peduncle longer than high, with dorsal surface almost flat; dorsum of node convex. Subpetiolar process small and triangular, located near propodeum. Petiolar spiracle located at mid-length of peduncle. Postpetiole globular and distinctly wider than petiole, as high as petiolar node in lateral view.

Frons with two to three pairs of longitudinal rugulae; irregular rugulae in several specimens. Dorsum of head between frontal carina and eye reticulate-rugose. Clypeus with one median longitudinal rugula and one or two rugulae laterally. Pronotum dorsally reticulate with shiny interspaces, laterally with reticulate or longitudinal rugulae. Dorsum of mesoscutum and mesoscutellar disc with longitudinal rugulae. Mesopleuron, metapleuron and lateral propodeum with longitudinal rugae. Dorsum of propodeum with rugulae; declivity smooth and shiny. Dorsal surface of petiolar peduncle smooth and shiny; dorsal and lateral surfaces of node reticulate-rugose. Postpetiole reticulate-rugose. First gastral tergite smooth, with some short basigastral costulae.

Dorsal surface of head with suberect setae. Two standing setae present around posterolateral corner of head. Scape with suberect setae. Outer margin of mandible with decumbent setae. Pronotum and mesonotum with long suberect setae and short suberect to decumbent setae. Dorsal surface of propodeal spine with decumbent setae. Petiolar peduncle with decumbent setae; node with longer decumbent setae. Postpetiole with decumbent setae; subpostpetiolar process with suberect setae. Gaster with decumbent to suberect setae.

Colour yellowish-brown; first gastral tergite with broad brown band.

Etymology.

The species name refers to the upwardly directed propodeal spine of the species.

Distribution and biology.

This species is known only from the type locality of Cambodia. The nest series was collected from a dead twig on lower vegetation (Fig. 18 ). As Bolton (1991) suggested that R. recava appeared to be polygynous, the colony of R. epispina found inside the dead twig also involved two dealate queens.

Remarks.

This species is similar to R. stenoceps , but can be distinguished by the propodeal spine directed upwards and the long peduncle of the petiole.

Figures

Figure 18. Forest habitats on secondary forest, Kampong Thom Province, Cambodia, type locality of R. epispina sp. nov. (S. Hosoishi).

Figures 1 - 6. Rotastruma epispina sp. nov., worker. 1, Mouthparts [1]; 2, Left mandible [2]; 3, Clypeus [3, 4, 5, 6]; 4, Full-face view of head [7, 8, 9, 18]; 5, Mesosoma in profile view [10, 11, 12, 18]; 6, Mesosoma in dorsal view [10, 18]. Figures in brackets correspond to diagnostic characters (Appendix 1).

Figures 7 - 11. Rotastruma epispina sp. nov., worker. 7, Mesosoma in ventral view [13]; 8, Middle tibia [14]; 9, Hind tibia [14]; 10, Petiole and postpetiole in profile view [15, 16]; 11, Sting in profile view [17]. Figures in brackets correspond to diagnostic characters (Appendix 1).

Figures 12 - 14. Rotastruma epispina sp. nov., holotype worker (KUEC) from Cambodia (HW 0.62; WL 0.84). 12, Body in profile view; 13, Full-face view of head; 14, Dorsal view of body.

Figures 15 - 17. Rotastruma epispina sp. nov., paratype queen (KUEC) from Cambodia (HW 0.68; WL 1.10). 15, Body in profile view; 16, Full-face view of head; 17, Dorsal view of body.