Strumigenys delicata, Tang & Guénard, 2023

Tang, Kit Lam & Guénard, Benoit, 2023, Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species, European Journal of Taxonomy 907, pp. 1-144 : 36-38

Strumigenys delicata sp. nov.

urn:lsid:zoobank.org:act:856F2DE2-52DE-4D67-9C06-77446477FA34

Fig. 11 ; Tables 2 , 6

Diagnosis

Strumigenys delicata sp. nov. can be distinguished from other species in the S. leptothrix -group by a combination of the following characters: cephalic, clypeal and mandibular dorsum with appressed short fine setae; long laterally-projecting setae present in full-face view; in profile view, standing setae appeared sporadically across cephalic dorsum, not restricted to area between highest point of vertex and occipital margin; pronotum marginated dorsolaterally; in profile view, propodeal spines subtended by broad lamellae; femora, tibiae and basitarsi with long fine erect setae.

Etymology

The species is named after its fine and apically-acute pilosity. The epithet ‘ delicata ’ is the nominative feminine singular of the Latin adjective ‘ delicatus ’.

Type material

Holotype worker ( Fig. 11 )

THAILAND • Trang Province, Khao Chong, Site 12 (KCW12-1); 7.5436° N, 99.8067° E; 27 Dec. 2018; IBBL members leg.; Winkler, 4 corners; primary forest; LKCNHM ANTWEB1011999 (collection code IBBL KCW-S12-ST-sp2).

Measurements

Holotype worker

TL 2.5, HL 0.65, HW 0.46, MandL 0.09, SL 0.32, EL 0.082, PW 0.24, ML 0.66, PL 0.30, PH 0.14, DPW 0.12, PPL 0.17, GL 0.65, CI 70, MI 14, SI 71, OI 18, LPI 46, DPI 38.

Worker description

HEAD. In full-face view, occipital margin deeply concave; occipital corners well developed and bluntly angular; occipital carina present. Clypeus about as broad as long, roughly resembling inverted diamond. Scapes subcylindrical, marginated but not converging anteriorly to form thin lamella at leading edge. Mandibles in full-face view triangular; masticatory margins engaged across entire length, without diastema or gap between mandibles. In profile view, eye with four ommatidia in diameter.

MESOSOMA. In profile view, promesonotal dorsum weakly convex, propodeum more or less flat transversely; pronotum marginated dorsolaterally. In dorsal view, lateral margins of pronotum broadly convex. In profile view, propodeal spines elongated-triangular, subtended on each side by broad lamella with concave posterior margin that broadens basally into rounded convex propodeal lobe. Metapleural gland bulla well developed.

METASOMA. In profile view, petiolar peduncle grading evenly into node, and about as long as (or slightly shorter than) node. In dorsal view, petiolar node longer than broad, around 1.6 times as long; disc of postpetiole slightly broader than long, around 1.2 times as long. Areolate processes (spongiform tissues) present on both petiole and postpetiole; ventral lobes of petiole and postpetiole extensive; lateral lobe of petiole forming moderately extensive flap at posterolateral angle of node in profile; in dorsal view, processes present along lateral and posterior margins of petiolar node, and surrounding disc of postpetiole, thicker along lateral and posterior margins than on anterior margin.

PILOSITY. In full-face view, short appressed fine setae present on cephalic, clypeal and mandibular dorsum, those on clypeal and mandibular dorsum shorter; masticatory margins each with row of medially-directed fine setae. Surface of antennae with decumbent to appressed short fine setae; decumbent fine setae also present along dorsolateral margin of head; long laterally-projecting fine setae present on lateral margin of occipital lobe; one similar seta also present on th upper scrobe margin behind level of eye. In dorsal view, promesonotal dorsum sparsely with appressed fine setae; posteriorly-directed decumbent setae present along lateral margins; pronotal humeral seta long and fine, mostly straight. In profile view, erect to suberect setae present sporadically throughout cephalic dorsum, not restricted to area between highest point of vertex and occipital margin; long fine erect to suberect setae also present on mesonotal dorsum in three pairs, on petiole, disc of postpetiole and all over gastral tergites, those on anterior portion of first gastral tergite coarser than those on rest of gaster; ventral surface of head and gaster with decumbent setae. Hairwheel present at mesopleural excavation. Surfaces of middle and hind femora, tibiae and basitarsi with long fine erect setae.

SCULPTURE. Cephalic dorsum, clypeal dorsum and ventral surface of head sparsely reticulate-rugulose, with spaces between rugulae densely areolate-rugulose; surface of antennal scrobe, antenna and legs densely areolate. Promesonotal dorsum predominantly areolate, with weak longitudinal rugulae and long, weak, longitudinal median striation; propodeal dorsum densely areolate-rugulose; dorsum of petiolar node transversely areolate-rugulose. Side of pronotum mostly smooth and shining, with weak rugulae around margins; pleurae and side of propodeum densely areolate-rugulose. Disc of postpetiole mostly smooth and shining. Basigastral costulae short, around one fourth in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys delicata sp. nov. is a member of the S. leptothrix -group and shares all its characters ( Bolton 2000), and very likely belongs to the elegantula -complex. The only specimen has fully-closed mandibles and observation is obscured by setae along the inner margin of the mandible, making an accurate assessment of the dentition difficult. Placing the specimen against backlight suggests the presence of a principal dental row of around eight alternating short and long teeth, followed by a series of smaller teeth and denticles, terminating in a small apical tooth.

Aside from Strumigenys delicata sp. nov., there are six other SEA species from the same species group ( S. ailaoshana , S. densissima sp. nov., S. elegantula , S. intermedia sp. nov., S. nankunshana and S. zhenghuii sp. nov.) that share the following characters: both appressed and erect setae present on cephalic dorsum, pronotum marginate dorsolaterally, propodeal spines present and subtended by broad lamellae ( Table 6 ). For S. delicata , its pronotum dorsum is areolate-rugulose (instead of predominantly longitudinally-striated as in S. ailaoshana , or predominantly transversely-striated as in S. nankunshana ); erect setae are present sporadically across the cephalic dorsum (instead of restricted to the area between the highest point of the vertex and the occipital margin as in S. densissima or S. elegantula ). Unlike all of the above six species, all the setae, including those on the cephalic dorsum, the clypeal dorsum, the mandibular dorsum, the surface of the legs, the petiole, postpetiole and gaster, are fine and apically-acute (instead of ranging from stout and truncated to various spatulatiform in shape). See comments under S. intermedia for a detailed comparison between the newly described species and the existing species from S. leptothrix -group.

Geographic range

Thailand (Trang).

Ecology

Collected from primary forest.

Figures

Fig. 11. Holotype worker (ANTWEB1011999) of Strumigenys delicata sp. nov. A. Full-face view. B. Profile view. C. Dorsal view.