Strumigenys formosa

This species was originally described from queens and the worker remained unknown until Tang et al. (2019) found a single worker in Hong Kong. This worker was collected in a secondary forest at an elevation of 162 m.

Identification
A member of the Strumigenys murphyi-group.

Teriyamu et al. (1995) - This species resembles Strumigenys hirashimai, but is easily separable from the latter in female by the absence of large flattened hairs on vertex and mesonotal dorsum (in hirashimai large flattened hairs abundant on dorsa of head and mesonotum), the absence of spoon-shaped hairs on dorsum of metanotum (in hirashimai with small spoon-shaped hairs), and acute upper posterior corner of propodeal lamellae (in hirashimai upper posterior corner of propodeal lamellae rounded).

Distribution
Hong Kong, Taiwan. This record of S. formosa represents the second record for this species and the first outside of Taiwan. Therefore, this species should not be considered as endemic to Taiwan (Tang et al., 2019).

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan. Palaearctic Region: China.

Nomenclature

 *  formosa. Epitritus formosus Terayama, Lin & Wu, 1995: 85, figs. 1-4 (q.) TAIWAN. Combination in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 120. See also: Bolton, 2000: 452.

Taxonomic Notes
Tang et al. (2019): The specimen clearly shares all characters of the S. murphyi-group (Bolton 2000) for which five species occur within the Oriental realm. The absence of flattened hairs on the inner margin of the mandibles distinguishes it from Strumigenys dyschima, Strumigenys hemisobek, and Strumigenys murphyi. All hairs on the scape are curved toward the basis of the scape, in contrast to Strumigenys nannosobek, which has hairs that are pointing towards the apex. On the Hong Kong specimen, the posterior margin of the head is deeply concave, contrary to other species of the S. murphyi-group except for S. formosa (based on the queen description), which also lacks flattened hairs on the inner margin of the mandibles and has a similar disposition and orientation of spoon-shaped hairs on the scape.

Queen
Holotype. HL 0.35 mm; HW 0.40 mm; SL 0.23 mm; ML 0.13 mm; CI 114; SI 58; MI 37; WL 0.48mm; AW 0.28mm; TL 1.5mm.

Head wider than long, widest at about the midlength, with shallowly convex posterior border in frontal view; frons microreticulate, with 15 appressed large orbicular hairs; vertex microreticulate, hairless. Mandibles slender in frontal view; apical half of inner margin with 4 minute teeth, of which basalmost largest; apicalmost with 2 small teeth, one at dorsal and the other at ventral. Clypeus wider than long, with transverse anterior border. Antennae with 6 segments; scape with a large anteriorly projecting subbasal lobe at the bent, anterior margin with a row of spoon-shaped hairs; 2nd segment longer than wide; 3rd and 4th segments each wider than long; 5th slightly longer than wide, and apical 3.0 x as long as wide. Compound eyes moderately prominent, 0.06 mm in diameter. Ocelli small, forming an obtuse triangle.

Dorsal outline of alitrunk straight in profile; pronotum weakly microreticulate; meso-metanotum microreticulate and scattered with short erect hairs. Propodeal lamellae moderately developed; upper posterior corner acute. Petiolar disc rectangular in dorsal view, 1.67 x as broad as long, with subdecumbent short hairs; postpetiolar disc 2.28 x as broad as long, with a pair of erect hairs and some subdecumbent hairs.

First gastral tergite with 3 transverse rows of long erect hairs, and many decumbent, curved, and short hairs; 2nd and 3rd tergites each with a transverse row of long erect hairs, and many decumbent, curved, and short hairs.

Ground color yellow; ocellar triangular area blackish brown.