Myrmecina andalas, Satria & Yamane, 2019

Satria, R. & Yamane, Sk., 2019, Two new species of the ant genus Myrmecina (Hymenoptera: Formicidae: Myrmicinae) from Sumatra, Zoosystematica Rossica (China) 28 (1), pp. 183-193 : 185-188

Myrmecina andalas sp.nov.

( Figs 1, 2, 3, 4)

Holotype. Worker, Indonesia, Sumatra, Aceh, Leuser Ecosystem, Putri Betung , Gunung Kemiri, N 3°49'521'', E 97°31'198'', alt. ca. 950−1200 m, 19.IX.2012, R. Satria leg., individual code: SEMU- T20180326A ( MZB).

Paratypes. One worker (SEMUT20180731A), same data as for holotype ( RSC) ; 3 workers (SKYUSI-FOR001–003), Leuser Ecosystem, Gunung Kemiri, alt. 1200 m, good forest, 20.IX.2012, Yamane & Syaukani leg. ( SKYC) ; 1 ergatoid queen (SEMUT20180731B), same data as for holotype ( RSC) .

Worker measurements and indices. Holotype and paratypes (n = 3): HL 0.90 mm, HW 1.00− 1.02 mm, MDL 0.50−0.52 mm, EL 0.24 mm, SL 0.94 mm, WL 1.19−1.20 mm, PNW 0.66−0.68 mm, PSL 0.12−0.13 mm, PTH 0.27−0.28 mm, PTL 0.26 mm, CI 111−113, MDI 55−57, SI 92−94, PTHI 103−107.

Worker description. Relatively large (HL 0.90 mm, HW 1.00− 1.02 mm, WL 1.19−1.20 mm). Head in frontal view rectangular, slightly shorter than broad, with posterior margin almost straight ( Fig. 3A); lateral sides of head shallowly convex. Clypeus consisting of flat dorsal disc and steep anterior face, laterally serrate; its anterior margin almost straight, with small median tooth and pair of lateral denticles. Labrum with pair of apical processes. Eye relatively large (EL 0.24 mm; 72– 73 ommatidia), distinctly breaking lateral margin of head, in profile occupying almost 1/4 length of head. Mandible triangular; masticatory margin with large apical and smaller preapical teeth, followed by 6 denticles. Antenna 12-segmented, with 3-segmented club; apical segment slightly longer than segments 10 and 11 combined; scape relatively long, distinctly surpassing posterolateral corner of head. Mesosoma in lateral view short and stout, with dorsal outline evenly convex; anterior ventrolateral portion of pronotum forming distinct process; mesonotum completely fused with pronotum; lower portion of mesopleuron broadly concave anteriorly (red arrow in Fig. 3B); mesopleuron not differentiated from metapleuron. Propodeum in dorsal view weakly demarcated anteriorly, but metanotal groove indistinct; anterior pair of denticles present on propodeal dorsum, very small and short (difficult to distinguish them from longitudinal rugae on propodeum) (red arrow in Fig. 2A); propodeal spine triangular, much shorter than broad and pointing dorsally; propodeal declivity almost vertical with lateral carinae well developed, with posterodorsal angle about 90°; posteriormost portion of propodeum with high lateral walls (propodeal lobes) ( Figs 3B, 3C, 3D). Petiole in dorsal view as broad as long, rectangular; its anterior slope in profile almost straight, dorsal face flat to weakly concave, and ventral outline straight with a small anterior denticle; postpetiole in dorsal view much broader than long, broader than petiole; sternopostpetiolar process absent. Gaster in dorsal view slightly elongate circular; anterior margin of first gastral tergite straight, with anterolateral corner very weakly angled. Mid- and hind tibiae broad and long, 3.5 times as long as broad.

Head dorsally with coarse longitudinal rugae; those on lateral part of head running posterolaterally toward posterolateral corner of head; interspaces between lateral rugae superficially sculptured and shiny; flat dorsal disc of clypeus smooth and shiny, with irregular punctures around anterolateral corner; ventrolateral area (temple + gena) of head smooth and shiny, with 1–2 longitudinal rugae (see Fig. 1A). Mesosoma, petiole and postpetiole with coarse irregular longitudinal rugae; declivity and posteriormost part of propodeun smooth and shiny. Gaster smooth and shiny.

Body covered with abundant long erect setae; clypeus with several long setae and a pair of long setae arising from median tooth of its anterior margin; scape with many suberect to erect setae that are longer than scape width (some of them as long as eye); all legs with numerous suberect to erect setae.

For color pattern see Figs 1−3; mesosoma, petiole and postpetiole dark reddish brown; head and gaster blackish brown, with apex of gaster orange. Mandible, clypeus, antenna and all legs reddish brown to brown, with antennal flagellum, tibiae and tarsi paler.

Ergatoid queen measurements and indices. Paratype (n = 1): HL 0.92 mm, HW 1.09 mm, MDL 0.54 mm, EL 0.27 mm, OED 0.39 mm, SL 0.97 mm, WL 1.30 mm, PNW 0.72 mm, PSL 0.16 mm, PTH 0.29 mm, PTL 0.26 mm, CI 118, MDI 58, SI 88, PTHI 111.

Ergatoid queen description. Very similar to worker including size, but differentiated from worker as follows: size of eye and number of ommatidia larger than in worker (EL 0.27 mm; 85 ommatidia); three ocelli present ( Fig. 4A); dorsal outline of mesosoma in lateral view more convex than in worker; small hole present at forewing position on mesosoma (blue arrow in Fig. 4B) near small round pale area (red arrow in Fig. 4B).

Comparative remarks. Myrmecina andalas sp. nov. is morphologically most similar to M. magnificens Wong et Guénard, 2016 among the species known from Sundaland. However, it is distinguishable from the latter by the following characteristics of worker: ventrolateral area of head (temple + gena) smooth and shiny; anterior pair of denticles on propodeal dorsum very small and short (distinct in M. magnificens ); propodeal spine triangular, much shorter than broad at base and pointing dorsad; propodeal declivity vertical, with posterodorsal angle almost 90°; sternopostpetiolar process absent. Worker of M. andalas sp. nov. also resembles that of M. nipponica Wheeler, 1906 . However, it is easily separated from the latter by the much larger eye that is more than twice as long as the antennal pedicel (vs. eye small, as long as pedicel), long erect setae on scape, some of which are 1.5 times as long as scape width (vs. most erect setae very short, not longer than scape length), and the propodeal lobe dorsally roundly convex (vs. in shape of a narrow strip).

The ergatoid queen in Asian Myrmecina has also been found in M. nipponica ( Ohkawara et al., 1993; Miyazaki et al., 2005; Peeters, 2012) and in undescribed species from Java ( Ito, 1996). Despite the difficulty in recognizing the ergatoid queen among dead specimens, some morphological characters are used for the recognition of ergatoid queen, such as the presence of ocelli and vestiges of wing articulation on mesosoma ( Fig. 4). The vestige of wing articulation was observed in the ergatoid queen of M. andalas as a small hole in place of the forewing near small round pale area on the mesosoma, and the same feature was also reported in ergatoid queens of M. nipponica which were determined by a direct observation of the ovaries and spermatheca ( Ohkawara et al., 1993). The ergatoid queen has developed eyes as in the dealate queen, but smaller in body size with a smaller number of ommatidia than in the dealate queen. On the other hand, the worker has smallest eyes and number of ommatidia among the three castes, but ommatidia each being larger than those in both the dealate queen and ergatoid queen in M. nipponica (Miyazaki et al., 2015). Although in M. andalas the ergatoid queen has larger eyes and number of ommatidia than in the worker, the size of each ommatidium was similar in both castes.

Etymology. The specific epithet is a previous name of Sumatra Island.

Distribution. So far known only from Sumatra.

Bionomics. No information about the biology of this species is available, except that specimens were collected from leaf litter in secondary forests.