Sathytes simplex Löbl, 1979

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 134-135

Sathytes simplex Löbl, 1979

( Figs 58 , 84B , 97A–C )

Chinese common name: ÊƟḛà甲

Sathytes simplex Löbl, 1979: 298 ; figs 19, 35. Type locality: Inde, Darjeeling distr. , Tiger Hill, 2150 m.

Additional material examined (6 exx.). 5 ♂♂, ‘ China: Xizang, Nyingchi City, pass nr. Yigong Tea Farm , 30°10’14”N, 94°55’51”E, 2200–2400 m, 11.vii.2021, Peng, Yin & Zhang, Ʊ Ẫffż 波ṁ县ƌŭē厂 ’; 1 ♂ ‘China: Xizang, Nyingchi City, Pailong Township , 30°0’35”N, 94°57’58”E, 2180 m, 10.vii.2021, Z. Peng, Z. Yin & W. Zhang leg. Ʊ Ẫh 治区ffż市ḦË乡 ’ (all in SNUC) .

Diagnosis. Male. Body length 2.45–2.6 mm; ratio (length/width) of head 1.04–1.16, pronotum 1.00–1.06, elytra 0.76–0.86, length of eye/tempus 0.86–0.91. Antennae simple, antennomere 9 slightly longer than wide (length/ width 1.06–1.15), lacking hyaline apophysis on mesal margin, antennomere 11 elongate (length/width 1.76–1.95), lacking protuberance at base. Aedeagus broad, slightly constricted at middle, apical margin slightly protuberant at left side. Female. See Löbl 1979.

Redescription (based on populations of China, measurements of original description included in parentheses). Male. Body ( Fig. 58A ) length 2.45–2.56 (2.55–2.60) mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with short pubescence.

Head ( Fig. 58B ) sub-rectangular at base, slightly longer than wide, length 0.53–0.58 mm, width across eyes 0.48–0.50 mm, length/width 1.10–1.16 (1.04); vertex weakly raised, with small asetose foveae (dorsal tentorial pits) located slightly posterior to level of posterior margin of eyes; frons anteriorly confluent with strongly declining clypeus, flat; clypeus with smooth surface, anterior margin carinate and moderately raised; ocular-mandibular carina thin and short; postgenal region strongly projecting. Venter with small, broadly separated gular foveae (posterior tentorial pits), lacking median carina or sulcus. Compound eyes prominent, composed of approximately 18 large ommatidia, length of eye/tempus 0.86–0.91. Antenna elongate, length 1.27–1.28 mm, distinct club ( Fig. 58C ) formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each transverse, 2 slightly broader and 8 slightly narrower than 3–7, 9 enlarged, slightly longer than wide, length/width 1.06–1.15, lacking hyaline apophysis on mesal margin, 10 transverse, length/width 0.82–0.87, 11 largest, slightly longer than 9 and 10 combined (36/33), length/width 1.76–1.95 (1.9), lacking protuberance at base.

Pronotum ( Fig. 58B ) approximately as long as wide, both length and width 0.56–0.57 mm, length/width 1.00 (1.06), widest at middle; lateral margins rounded, convergent apically and basally; disc weakly convex; asetose lateral antebasal foveae distinct. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; hypomeral ridge absent; margin of coxal cavity moderately carinate.

Elytra much wider than long, length 0.72–0.74 mm, width 0.84–0.92 mm, length/width 0.80–0.86 (0.76); each elytron with four large, asetose basal foveae; lacking discal stria; humerus slightly angulate, subhumeral fovea present, marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by strongly curved carinae; median mesoventral foveae contiguous, originating from shared oval opening, large lateral mesoventral foveae forked internally, mesoventral process short, with complete marginal stria. Metaventrite weakly prominent admesally, inclined towards middle, with well-developed lateral mesocoxal and two lateral metaventral foveae, with moderately large, round median pit shortly anterior to posterior margin, posterior margin broadly emarginate and shallowly incised at middle.

Legs elongate, simple.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.64–0.72 mm, width 0.77–0.83 mm. Tergite 1 (IV) more than twice as long as 2 (V), lacking basal sulcus, with one pair of mediobasal and two pairs of basolateral foveae, lacking discal or marginal carina; tergite 2 (V) slightly longer than 3 (VI), 4 (VII) longer than 3 but much shorter than 2 and 3 combined; tergites 2–3 (IV–VI) each with one pair of mediobasal and two pairs of basolateral foveae, 4 with one pair of basolateral foveae and marginal tubercles, tergite 5 (VIII) semicircular, transverse, posterior margin roundly emarginate at middle. Sternites depressed along middle; sternite 2 (IV) with one pair of mediobasal and three pairs of basolateral foveae, lateral carina absent; midlength of sternites 2–5 (IV–VII) gradually shorter, sternites 3–4 (IV–VI) each with three pairs and 5 (VII) with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 58D ) moderately sclerotized, elongate, apex with three elongate setae.

Aedeagus ( Fig. 58E ) 0.29 (0.26) mm long, slightly asymmetric, broad, plate-like; median lobe with large foramen, slightly constricted at middle, apical margin slightly protuberant at left side.

Female. No material has been collected in China, see Löbl 1979 for description.

Comparative notes. Sathytes simplex is the only species of the genus known to possess simple antennae in the male.

Distribution. Darjeeling District, N India; Bomê County and Chagyib District (Nyingchi), Xizang, SW China ( Figs 84B , 97A–C ). By discovering the new populations in China, the known range of this species extends considerably for some 750 km to the northeast. New country record for China.

Remarks. Even when adjusted to a same angle, the aedeagi of the populations from China appear to be less protuberant at the apical margin than is shown in Löbl (1979: fig. 35). However, this difference could be reasonably fall into the range of intraspecific variation. The measurements of the body segments show no significant difference from those of specimens from northern India. The populations of China are temporarily identified as conspecific with S. simplex . A direct comparison with the holotype in the future is desired, since in many cases this is the only means to distinguish morphologically similar species within Sathytes .

Figures

FIGURE 58. Morphology of Sathytes simplex Löbl, male. A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Sternite 7 (IX). E. Aedeagus, ventral. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, E; 0.1 mm in D.

FIGURE 84. Distribution of Tibetan Batrisini. A. Sathytes magnus Yin & Li (circle), S. panzhaohuii Yin & Shen (triangle) and S. pengzhongi sp. nov. (square). B. S. proclivis sp. nov. (circle), S. pseudograndis sp. nov. (triangle) and S. simplex Löbl (square). C. S. sympatricus sp. nov. (circle), S. transversus Yin & Shen (triangle) and S. virupaksa sp. nov. (square).

FIGURE 97. Environment of and collecting sites at Nyingchi area. A. Sign of Yigong Tea Farm (ƌŭē厂). B. Forest near Yigong. C. Forest at Pailong Township (ḦË乡). D. Forest near Tongmai Town (ȃ9W).