Strumigenys xenopilus, 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 : 120-123

Strumigenys xenopilus sp. nov.

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Fig. 40 ; Table 2

Diagnosis

Strumigenys xenopilus sp. nov. can be distinguished from all other species of Strumigenys in Southeast Asia by a combination of the following characters: surface of head, scape, promesonotum, petiole, postpetiole, anterior and posterior portions of gaster with appressed obovate setae; mandibles short and triangular, without diastema or gap between mandibles; scape dorsoventrally flattened with anteriorlyprojected small subbasal lobe; eyes reduced; side of mesosoma mostly smooth and shining; propodeal lamellae broad.

Etymology

The species is named after its peculiar pilosity on the gaster. The name was created by combining the prefix ‘ xeno ’ (meaning ‘foreign’) with ‘ pilus ’, the nominative singular of Latin noun ‘ pilus ’ (meaning ‘hair’).

Type material

Holotype worker ( Fig. 40 )

MAINLAND CHINA • Hainan Province, Yinggeling , YGLK12; 19.08446° N, 109.50425° E; 2 Aug. 2016; L. Wang leg.; Winkler, 4 corners; secondary forest; LKCNHM ANTWEB1011877 (collection code IBBL HNA-00363).

Measurements

Holotype worker

TL 2.0, HL 0.48, HW 0.39, MandL 0.12, SL 0.23, EL 0.027, PW 0.22, ML 0.52, PL 0.22, PH 0.13, DPW 0.11, PPL 0.14, GL 0.48, CI 82, MI 25, SI 59, OI 7, LPI 56, DPI 50.

Worker description

HEAD. In full-face view, occipital margin broadly concave; occipital corners well developed and bluntly angular; occipital carina narrow; dorsolateral margin of head broadly convex, lateral margin of occipital lobe and upper scrobe margin not forming blunt angle. Anterior clypeal margin broadly convex, with rounded anterolateral angles. Scape dorsoventrally flattened, basally narrow followed by anteriorlyprojected small subbasal lobe; trailing edge transverse to very shallowly concave. Mandibles in full-face view triangular; masticatory margins engaged across entire length, without diastema or gap between mandibles. In profile view, eye greatly reduced, located just above ventral margin of antennal scrobe.

MESOSOMA. In profile view, promesonotal dorsum broadly convex, propodeum more or less flat transversely. Pronotum very weakly marginated dorsolaterally. In dorsal view, lateral margins of pronotum evenly convex. Propodeal teeth present but inconspicuous, subtended on each side by broad lamella with mostly straight posterior margin, transit gently into propodeal lobe with equally straight posterior margin. Metapleural gland bulla well developed.

METASOMA. In profile view, petiolar node high; petiolar peduncle not grading evenly into node, longer than node, around 1.2 times as long; petiolar node with differentiated anterior face. In dorsal view, node broader than long, around 1.2 times as long; disc of postpetiole broader than long, around 1.7 times as long. Areolate processes (spongiform tissues) present on both petiole and postpetiole; ventral lobes of petiole and postpetiole extensive; lateral lobe of petiole merely a 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 around posterolateral angles than on rest of margins.

PILOSITY. Surfaces of head (including ventral surface and clypeal dorsum, but excluding antennal scrobe) and scape covered with appressed obovate setae; mandibular dorsum with small appressed obovate to oblanceolate setae. In full-face view, laterally-projecting seta absent; appressed setae on the clypeal and mandibular dorsum much denser than on remaining surface of head; dorsolateral margin of head with continuous row of anteriorly-directed spoon-shaped setae; similar setae present on lateral and anterior clypeal margin, and on leading edge of scape directed apically; funiculus (except for apical antennomere) covered with short appressed fine setae, apical antennomere covered with short appressed narrowly elliptic to fine setae. Pronotal humeral seta absent. In profile view, erect seta absent on dorsal surface of head or mesosoma. Promesonotal dorsum, dorsum of petiolar node and postpetiole, near anterior and posterior margin of first gastral tergite covered with appressed obovate setae; remaining gastral tergites with appressed obovate to spatulate setae, and transit to suberect remiform setae towards pygidium; suberect to decumbent, subspatulate to narrowly elliptic setae covering gastral sternites; very short appressed fine setae also present sporadically across the surface of gaster but inconspicuous ( Fig. 40B– C ). Hairwheel present at mesopleural excavation. Surfaces of legs without any laterally-projecting setae; femora covered with appressed oblong to subspatulate setae; tibiae covered with appressed subspatulate setae.

SCULPTURE. Cephalic dorsum (including antennal scrobe), surface of antenna and legs, mesosomal dorsum and dorsum of petiolar node densely areolate. Side of mesosoma mostly smooth and shining, with vestiges of sculpture around margins. Disc of postpetiole smooth and shining. Basigastral costulae short, around one fourth in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys xenopilus sp. nov. is well distinguished from other species of Strumigenys by its peculiar pilosity in combination with its mandibles and broad flattened scape. It does not belong to any existing Strumigenys species group, and is most likely a member of its own species group.

Strumigenys xenopilus sp. nov. shares similar short triangular mandibles with the S. leptothrix -group, and appressed spatulate setae with a few species from the group, but it also has a broad flattened scape, which is absent in all species of the S. leptothrix -group. Appressed spatulate setae are present on the surface of the gastral tergites of S. xenopilus , in contrast, species of the S. leptothrix -group have stout standing setae instead.

On the other hand, a broad flattened scape is a common feature among species of the S. circothrix - group and S. argiola -group. However, their pilosity is predominantly orbicular setae instead of obovate or spatulate setae. The former group has narrow and apically-tapered mandibles while the latter has curvilinear mandibles, both of which have a prominent gap between the mandibles. Strumigenys xenopilus sp. nov. has short triangular mandibles with masticatory margins that engage across entire length instead.

Strumigenys xenopilus sp. nov. does not belong to the S. rostrata -group either. It lacks the basally-directed seta on the leading edge of scape or any pronotal humeral seta, both of which are typical in species of the S. rostrata -group. Its scape is also strongly dorsoventrally flattened with an anteriorlyprojected small subbasal lobe, in contrast with the weakly to moderately dorsoventrally flattened scape with a thin flange at the leading edge of the S. rostrata -group.

Geographic range

Mainland China (Hainan).

Ecology

Collected in secondary forest.

Figures

Fig. 40. Holotype worker (ANTWEB1011877) of Strumigenys xenopilus sp. nov. A. Full-face view. B. Gaster close-up in dorsal view. C. Gaster close-up in ventral view. D. Profile view. E. Dorsal view.