Tibetyrus formicarius Yin & Lin, 2020

Yin, Zi-Wei & Lin, Ye-Jie, 2020, Tibetyrus gen. nov., a new myrmecophilous Tyrini from Xizang, China (Coleoptera: Staphylinidae: Pselaphinae), Zootaxa 4786 (1), pp. 131-137 : 133-136

Tibetyrus formicarius Yin & Lin , sp. nov.

( Figs 1–3 )

Type material. HOLOTYPE: CHINA: ♂, ‘China: Xizang, Nyingchi, Gongbo'gyamda Co., Bahe Town , Jiare Vill., Jiarelongba , 30.0075º N, 93.7818º E, 3,485 m, 18.x.2019, Lin Y-J, TŨỮḔDZOiDZAEÙDZAEȐDZ’ ( SNUC). PARATYTYPES: CHINA: 2 ♀♀, same collection data as holotype ( SNUC).

Description. Male ( Fig. 1A ). Body generally elongate, length (combined length of head, pronotum, elytra and abdomen) 3.71 mm, color uniformly reddish-brown; dorsal surface of whole body finely punctate, with short decumbent setae of elytra and abdomen slightly denser than those on head and pronotum.

Head ( Figs 1A , 2A ) lengthily and bluntly triangular, length from anterior margin of clypeus to head base 0.71 mm, width across eyes 0.57 mm; vertexal foveae at level of midline of eyes; frons dilated apically, longitudinally and smoothly impressed between antennal tubercles; postocular margins rounded, with tufts of dense setae on each side; eyes moderately prominent, each composed of about 15 facets. Maxillary palpi ( Fig. 1B ) with short, evenly distributed sensillar setae. Antennae elongate ( Fig. 1A ), length 2.30 mm; antennomeres 1 (scapes) distinctly longer than 2 (pedicels) and 3 combined, but shorter than combined length of antennomeres 2 to 4, approximately 1.8× as long as wide, antennomeres 2 and 3 of similar size, antennomeres 4–6 longer than 2, successively wider, antennomeres 7 slightly wider than 6, transverse, antennomeres 8 slightly narrower and much shorter than 7, antennomeres 9–11 ( Fig. 1C ) strongly enlarged to form distinct clubs, 9 about three times as long as and twice as wide as 8, 10 much larger than 9, broadly and deeply excavated on ventral surface, 11 much smaller than 10 and slightly larger than 9, their bases strongly elongate and constricted to form long projections, which extend downwards to exceed over half of antennomeres 10, with disk-like protuberance near bases of projections, basal portions of antennomeres 11 also circularly impressed, within impressions one fovea-like setose pit, apices much broader than bases and rounded.

Pronotum ( Figs 1A , 2A ) elongate, mid-length 0.76 mm, maximum width 0.66 mm, with slightly arcuate anterior and sinuate posterior margin, sides rounded at middle, then narrowing toward apex and subparallel in basal two-fifths.

Elytra ( Fig. 1A ) much wider than long, length along suture 0.89 mm, maximum width 1.15 mm, posterior margin with row of dense setae that are longer than those on disc. Mesoventrite ( Fig. 2B ) strongly transverse, with thin ridges lateral to middle; metaventrite also transverse, with large, lamina-like postero-submedial projections, posterior margin of each projection strongly curved ventrally to form large spine; setae of meso- and metaventrite much denser and longer in lateral areas than at middle.

Legs elongate, lacking modifications.

Abdomen about as long as wide, widest at posterior margin of tergite 1 (IV), mid-length 1.35 mm, maximum width 1.28 mm. Sternite 7 (IX) ( Fig. 2C ) semi-membranous, elongate, with round apex and dense apical setae.

Aedeagus ( Fig. 2 D–F) elongate, length 0.62 mm, median lobe with large, nearly symmetric basal capsule, apical half strongly twisted, narrowing apicad, forming pointed apex; endophallus complex in structure, composed of one elongate, broad, curved and weakly sclerotized plate-like sclerite abruptly narrowed and acute at apex, one relatively broad and bi-sinuate sclerite narrowing from basal two-thirds to apex, and one much shorter and thinner elongate sclerite near middle; parameres reduced and symmetric, lacking apical setae.

Female. General appearance similar to male; antennae shorter, clubs ( Fig. 1D ) unmodified; metaventrite lacking projections. Measurements (as for male): body length 3.50–3.71 mm, length/width of head 0.65–0.66/ 0.56 mm, pronotum 0.72–0.76/ 0.64–0.65 mm, elytra 0.85–0.91/ 1.15–1.19 mm, abdomen 1.27–1.39/ 1.33–1.36 mm, length of antennae 1.85 mm, antennomeres 1 approximately as long as 2–3 combined and 1.3× as long as wide; each eye composed of about 18 facets.

Distribution. Southwestern China: Xizang.

Biological and collection notes. The collection site is located near the entrance of a deep, north-south oriented valley named Jiarelongba, approximately 2 km north of Jiare Village, and 11 km west of Basongcuo Lake. The valley has abundant vegetation, with a broad pass and a creek on the west side ( Fig. 3C, D ). The field work was conducted at around 9:00 a.m. Two individuals of the pselaphid were first discovered in tunnels of an ant nest found under an approximately 30 cm 2 stone on the ground just beside the pass. Later a third individual was collected from another nest in the same area less than 50 m away. The host ant was later identified as a member of the genus Formica ( Fig. 3A, B; S.-Y . Zhou & H. Ran, pers. comm.). The new species is apparently myrmecophilous because of the repeated circumstances of its collection, and it may possibly be a synoekete or a symphile due to the presence of what may be paired trichomes on the postocular margin. Similar trichomes of the head are commonly found in many myrmecophilous pselaphine genera, especially in the tribe Batrisini . The markedly constricted elytral base and loss of hind wings are typical for various myrmecophilous/termitophilous beetle groups. However, additional field observations are necessary to further reveal the biology of the new species.

Etymology. The specific epithet recognizes the association between the new species and Formica ants.

Figures

FIGURE 1. Tibetyrus formicarius (A–C. Male. D. Female). A. Habitus. B. Right maxillary palpus. C, D. Antennomeres 9–11. Scale bars: 1.0 mm in A; 0.2 mm in B; 0.5 mm in C, D.

FIGURE 2. Tibetyrus formicarius, male. A. Head, pronotum, and elytral base. B. Meso- and metaventrite. C. Sternite 7 (IX). D–F. Aedeagus, in dorsal (D), lateral (E), and ventral (F) view. Scale bars: 0.5 mm in A, B; 0.1 mm in C; 0.2 mm in D–F.

FIGURE 3. Host ant (A, B) and collection environment (C, D) of Tibetyrus formicarius. A. Habitus, lateral. B. Head, in fullface view. C, D. Jiarelongba Valley, where the ant nests were found under stones beside the pass.