Strumigenys densissima, 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 : 38-41

Strumigenys densissima sp. nov.

urn:lsid:zoobank.org:act:A4D30AFB-F195-4666-9CDC-2CB0A81F760F

Fig. 12 ; Tables 2 , 6

Diagnosis

Strumigenys densissima sp. nov. can be distinguished from other species in the S. leptothrix -group by a combination of the following characters: cephalic dorsum with appressed stout and truncated setae; clypeal dorsum with appressed narrowly elliptic to acicular setae; in profile view, erect setae 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 erect setae.

Etymology

The species is named after its dense pilosity on the antennae. The epithet ‘ densissima ’ is the nominative feminine singular superlative of the Latin adjective ‘ densus ’ (meaning ‘dense’).

Type material

Holotype worker ( Fig. 12 )

MAINLAND CHINA • Yunnan Province, Jinghong ; 7–12 Aug. 2006; S. Onoda leg.; SWFC ANTWEB1010908 .

Paratype worker

MAINLAND CHINA • 1 worker; Yunnan Province, Dali; 29 Jul.–4 Aug. 2006; S. Onoda leg.; KUM ANTWEB1010907 .

Measurements

Holotype worker

TL 2.6, HL 0.65, HW 0.48, MandL 0.11, SL 0.30, EL 0.075, PW 0.27, ML 0.67, PL 0.31, PH 0.15, DPW 0.11, PPL 0.20, GL 0.67, CI 74, MI 16, SI 62, OI 16, LPI 49, DPI 37.

Paratype worker

TL 2.8, HL 0.69, HW 0.49, MandL 0.10, SL 0.31, EL 0.073, PW 0.26, ML 0.69, PL 0.37, PH 0.17, DPW 0.12, PPL 0.20, GL 0.74, CI 72, MI 15, SI 64, OI 15, LPI 46, DPI 33 (n= 1).

Worker description

HEAD. In full-face view, occipital margin deeply, broadly concave; occipital corners well developed and bluntly angular; occipital carina broad. Clypeus about as broad as long (or slightly broader than 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; basal lamellae low and broadly triangular, not fully visible at full closure. In profile view, eye with four ommatidia in diameter.

DENTITION ( Fig. 12B ). Principal dental row with eight alternating short triangular and long spiniform teeth (i.e., four consecutive pairs of teeth, each pair consists of short tooth followed by long tooth), second and third pairs subequal in size and longer than other pairs (short tooth of one pair compares with short tooth of another pair only, same for long tooth); followed by 3–4 small teeth and, at down curvature in anterior view, series of four minute denticles, terminating in small apical tooth. Total dental count of 16–17.

MESOSOMA. In profile view, promesonotal dorsum very weakly convex, propodeum more or less flat transversely; pronotum marginated dorsolaterally. In dorsal view, lateral margins of pronotum evenly 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 1.6–1.7 times as long; disc of postpetiole broader than long, around 1.3–1.5 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 te petiolar node, and surrounding disc of postpetiole, thicker along lateral and posterior margins than on anterior margin.

PILOSITY. In full-face view, cephalic dorsum with long, appressed stout and truncated setae; clypeal dorsum covered with narrowly elliptic to acicular setae; mandibular dorsum covered with acicular setae; masticatory margins each with row of medially-directed fine setae. Surface of scape covered with appressed acicular setae; funiculus densely covered with long fine setae. Lateral margin of occipital lobe with 3–5 laterally-projecting setae; dorsolateral margin of head and leading edge of scape with decumbent setae; appressed setae present along occipital margin. In dorsal view, promesonotal dorsum sparsely with appressed stout and truncated setae; posteriorly-directed decumbent setae present along lateral margins. Pronotal humeral seta long, straight and stout. In profile view, erect setae on cephalic dorsum restricted to area between highest point of vertex and th occipital margin; suberect to erect setae also present on mesonotal dorsum in three pairs, on petiole in two pairs, on disc of postpetiole in one pair and all over gastral tergites; similar but suberect to decumbent setae also present on gastral sternites; ventral surface of head with decumbent setae. Hairwheel present at mesopleural excavation. Surfaces of middle and hind femora, tibiae and basitarsi with long stout 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. Mesosomal dorsum predominantly densely areolate, with weak longitudinal rugulae and long, weak, longitudinal median striation; dorsum of petiolar node 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 third in length of first gastral tergite; rest of gaster smooth and shining.

Comments

Strumigenys densissima sp. nov. is a member of elegantula -complex in the S. leptothrix -group and shares all its characters ( Bolton 2000).

Aside from Strumigenys densissima sp. nov., there are six other SEA species from the same species group ( S. ailaoshana , S. delicata 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 ). The pronotum dorsum of S. densissima is areolate-rugulose (instead of predominantly longitudinally-striated as in S. ailaoshana , or predominantly transversely-striated as in S. nankunshana ); erect setae on the cephalic dorsum are restricted to the area between the highest point of the vertex and the occipital margin (instead of present sporadically across the cephalic dorsum as in S. delicata , S. intermedia or S. zhenghuii ); appressed setae on the cephalic dorsum are all long, stout and truncated (instead of short, fine and apically-acute setae as in S. delicata , or mostly subspatulate setae as in S. elegantula ).

Comparing with S. elegantula , the appressed setae of S. densissima sp. nov. on the clypeal dorsum are not drastically different from those on the cephalic dorsum in shape. In contrast, for S. elegantula , the setae on the clypeal dorsum clearly transit into narrowly elliptic ones. The setae on the funiculus are also much finer and denser in S. densissima in comparison with S. elegantula . See comments under S. intermedia sp. nov. for a detailed comparison between the newly described species and the existing species of S. leptothrix -group.

Geographic range

Mainland China (Yunnan).

Ecology

Collected in forest. No other information available.

Figures

Fig. 12. Type specimens of Strumigenys densissima sp. nov. A, C–D. Holotype worker (ANTWEB1010908). B. Paratype worker (ANTWEB1010907). A. Full-face view. B. Mandible closeup. C. Profile view. D. Dorsal view.