Myrmecina rugosodorsum Gu & Chen, 2025

Gu, Zhuojian, Zhang, Chen, Du, Congcong & Chen, Zhilin, 2025, Synopsis of the ant genus Myrmecina Curtis, 1829 from China (Hymenoptera, Formicidae, Myrmicinae), with description of eleven new species, Deutsche Entomologische Zeitschrift 72 (2), pp. 395-448 : 395-448

Myrmecina rugosodorsum Gu & Chen sp. nov.

Fig. 47

Material examined.

Holotype. • worker, Jinyunshan , Chongqing, China, 29.8073°N, 106.3897°E, 550 m, secondary forest, leaf litter, 28. VII. 2003, Jianhua Huang, GXNU 030551 [ GXNU] .

Diagnostic features.

(1) Posterolateral corners of head rounded and projecting; (2) clypeus with deeply arcuate anterior margin, bearing a tiny median denticle; (3) eumetanotal spines absent or vestigial; (4) petiole with triangular median dorsal projection and flat ventral margin; (5) postpetiole trapezoidal, lacking anterodorsal corner; (6) coarse irregular rugae on mesosomal dorsum (shared with M. shanyii Gu & Chen , sp. nov.), but latter lacks oblique frons rugae and punctate-rugulose lateroventral area of head.

Notes.

Comparing to other Myrmecina species, M. rugosodorsum Gu & Chen , sp. nov. is most similar to M. shanyii Gu & Chen , sp. nov. in possessing a rugose mesosomal dorsum and robust propodeal spines, but M. rugosodorsum Gu & Chen , sp. nov. can be unequivocally distinguished by the following traits: (1) the clypeal anterior margin in M. rugosodorsum Gu & Chen , sp. nov. is deeply and arcuately concave, with a tiny median denticle (vs. the clypeal anterior margin in M. shanyii Gu & Chen , sp. nov. is nearly straight margin, lacking a denticle), though both share projecting anterolateral clypeal corners; (2) posterolateral corners of head of rounded and projecting in M. rugosodorsum Gu & Chen , sp. nov. (vs. broadly rounded but not projecting in M. shanyii Gu & Chen , sp. nov.); (3) eumetanotal spines of M. rugosodorsum Gu & Chen , sp. nov. absent or extremely reduced (vs. stout, tooth-like, and projecting above dorsal outline in M. shanyii Gu & Chen , sp. nov.); (4) interspinal space of propodeal spines of M. rugosodorsum Gu & Chen , sp. nov. U-shaped (vs. broadly V-shaped in M. shanyii Gu & Chen , sp. nov.); (5) petiole with a triangular median dorsal projection and flat ventral margin (vs. posterodorsally directed tooth-like projection and convex ventral margin with subpetiolar process in M. shanyii Gu & Chen , sp. nov.); (6) postpetiole lacking an anterodorsal corner and not compressed anteroposteriorly (vs. strongly compressed with straight dorsal margin in M. shanyii Gu & Chen , sp. nov.); (7) while both species exhibit coarse irregular rugae on the mesosomal dorsum, M. rugosodorsum Gu & Chen , sp. nov. lacks the oblique posterolateral rugae on the frons and punctate-rugulose lateroventral head sculpture seen in M. shanyii Gu & Chen , sp. nov. M. rugosodorsum Gu & Chen , sp. nov. is also similar to M. padangensis from Indonesia, both of them possessing a rugose mesosomal dorsum. length of petiole nearly equal with its height in M. rugosodorsum Gu & Chen , sp. nov. (vs. the length of petiole approximately 1.5 times longer than its height in M. padangensis ).

Worker measurements.

(N = 1). HL 0.68, HW 0.63, CI 93, SL 0.57, SI 90, ED 0.09, MSL 0.81, PW 0.45, PL 0.17, PH 0.21, DPW 0.20, LPI 124, DPI 118, GL 0.87, TL 2.89.

Worker description.

Head. In full-face view, head rectangular, lateral margins nearly parallel, posterior margin deeply concave medially, posterolateral corners rounded and projecting. Mandibles with 7 teeth on masticatory margin: apical two teeth broad and prominent, teeth 3–6 minute and indistinct, basal tooth larger than teeth 3–6, but distinctly smaller than apical teeth. Clypeus with projecting anterolateral corners, anterior margin of clypeus deeply and arcuately concave, bearing a tiny median denticle. Frontal lobes well-developed, laterally expanded. 12 - segmented, scapes just reaching posterolateral corners. Eyes relatively large, composed of 16–18 ommatidia. Mesosoma. In lateral view, dorsal outline of mesosoma convex, eumetanotal spines absent or extremely reduced. Propodeal spines robust at base, acutely tapered apically, length slightly greater than their basal width. Propodeal spiracle moderate size, its diameter approximately 1 / 2 as its distance to propodeal declivity. In dorsal view, anterior margin of pronotum rounded and convex, anterolateral corners broadly rounded (not angular). Propodeal spines 1.5 times longer than their basal width; interspinal space U-shaped. Metasoma. In lateral view, petiole distinctly higher than long, dorsal margin with a triangular median projection; ventral margin flat. Postpetiole lacking a pronounced anterodorsal angle, not forming a distinct node; sternite trapezoidal. In dorsal view, petiole wider than long; postpetiole lacking anterolateral corners. Gaster oval. Sculpture. Mandibles and clypeus smooth and shining. Head in full-face view with coarse longitudinal rugae; lateroventral portion of head smooth and shining. Mesosomal dorsum with irregular rugae. Petiole and postpetiole with longitudinal striae; gaster smooth and shining. Pilosity and pubescence. Body densely covered with long erect hairs. Appressed pubescence restricted to antennal club. Coloration. Body dark brown to black; mandibles, antennae, and legs yellowish-brown.

Etymology.

The specific epithet “ rugosodorsum ” is a Latin neuter compound adjective, combining “ rugosus ” (wrinkled or rugose) and “ dorsum ” (the back or dorsum). It refers to the distinctly rugose dorsal surface of the mesosoma, a key diagnostic trait of this species.

Distribution.

Chongqing.

Figures

Figure 47. Myrmecina rugosodorsum Gu & Chen, sp. nov. A. Mesosoma in dorsal view; B. Head in full-face view; C. Body in dorsal view; D. Body in lateral view.