Ischnosoma, Stephens, 1829

Kocian, Matúš & Schülke, Michael, 2018, New species and records of Ischnosoma Stephens (Coleoptera: Staphylinidae: Tachyporinae) from Nepal, Zootaxa 4442 (4), pp. 501-522 : 519-520

Key to the Ischnosoma species of Nepal

1 Anterior margin of pronotum without carina; exceptionally such a carina may be present only in lateral portions of anterior margin; best seen with opposite light reflection. Ischnosoma convexum species-group............................... 2

- Anterior margin of pronotum with carina along all its length. Male sternite VIII with conspicuously modified palisade and beard-like setae. Ischnosoma pictum species group........................................................... 6

2 Pronotum distinctly bicoloured, anterior part with dark spot, posterior two-thirds rufotestaceous; head and elytra dark-brown to piceous, humeral spot and posterior margin of elytra rufotestaceous; abdomen rufotestaceous with darker transverse bands on tergites VI and VII. Abdomen from segment III strongly tapering towards apex. Dark setae on apical margin of male sternite VII more numerous (more than 4 on either side), close to the margin, inwards approaching the sternite margin and reaching the middle ( Fig. 28 ). Internal sac of aedeagus basally with two groups of 3–4 oblong finger-like sclerites...................................................................................... quadriguttatum quadriguttatum (Champion)

- Pronotum uniformly rufotestaceous; elytra dark with paler apical margin. Abdomen parallel-sided or only slightly tapering towards apex from segment V. Dark setae on apical margin of male sternite VII less numerous (no more than four on either side), distinctly separated and distant from margin, not reaching the middle of apical margin of sternite ( Figs 12 , 15 , 29, 30 ). Internal sac of aedeagus different......................................................................... 3

3 Smaller species, body length 3 mm. Discal row of punctures on elytra only with three punctures. Internal sac of aedeagus basally with two long and several smaller sclerites ( Fig. 17 ).......................................... hirthei sp.n.

- Larger species, body length 4–5 mm. Discal row of elytra with more than 5 punctures. Internal structures of aedeagus different..................................................................................................... 4

4 Posterior part of male sternite VIII without dark, long, and thick setae, only with shorter setae ( Fig. 31 ), median area without dark modified setae........................................................................ travei (Coiffait)

- Posterior part of male sternite VIII with dark long and thick setae ( Figs 13 , 16 ), median area with several dark and thicker modified setae....................................................................................... 5

5 Median area of male sternite VIII with cluster of denser and shorter pale setae.................... gratiosum (Cameron)

- Median area of male sternite VIII without cluster of denser and shorter pale setae, only with sparse and long pubescence ( Fig. 13 )...................................................................................... bhojpur sp. n.

6 Abdomen from segment III strongly tapering towards apex. Elytra at suture distinctly longer than pronotum, wider than pronotum. Macropterous and more colourful species with darker head and dark spot on elytra. Tergite VII with palisade fringe... 7

- Abdomen parallel-sided or only slightly tapering towards apex from segment V. Elytra at suture as long as pronotum or shorter, as wide as pronotum. Brachypterous or apterous, uniformly rufotestaceous to rufobrunneous species. Tergite VII without palisade fringe......................................................................................... 12

7 Elytra with two irregular discal rows of punctures. Head of male with large protuberant eyes........... duplicatum (Sharp)

- Elytra with one discal row of punctures. Shape of head without conspicuous sexual dimorphism, eyes similar in male and female............................................................................................. 8

8 Body conspicuously bicoloured: head, anterior part of pronotum, a characteristic saddle-like spot on elytra, and anterior parts of tergites brunneous. Clusters of modified palisade and beard-like setae on male sternite VIII large and long, arranged in about eight rows of palisade setae ( Fig. 35 ).................................................. fasciatocolle (Champion)

- Body either generally darker with dark pronotum and elytra, or less conspicuously bicoloured. Clusters of modified palisade and beard-like setae on male sternite VIII smaller, arranged in five rows of palisade setae at most..................... 9

9 Clusters of modified palisade and beard-like setae on male sternite VIII arranged in only one row of setae............. 10

- Clusters of modified palisade and beard-like setae on male sternite VIII arranged in 3–5 rows of palisade setae......... 11

10 Palisade setae on male sternite VIII arranged in one row along apical margin of sternite and forming two characteristic triangular patterns. Apical margin of male sternite VIII narrowly concave, median area of this sternite with sparse pubescence ( Fig. 19 ). Median area of male sternite VII in posterior part with large area without pubescence ( Fig. 18 ).......... schmidti sp.n.

- Palisade setae on male sternite VIII arranged in two isolated groups at the apical margin. Apical margin of male sternite VIII deeply concave, median area of this sternite in posterior part with field without pubescence delimited by bow-like suture ( Fig. 39 ), with cluster of very short setae in median portion. Median area of male sternite VII very sparsely punctate.................................................................................................... thamar Kocian

11 Clusters of modified palisade and beard-like setae on male sternite VIII small, arranged in only three rows of palisade setae ( Fig. 32 ), pubescence in median area long and sparse................................................. iob Kocian

- Clusters of modified palisade and beard-like setae on male sternite VIII larger, arranged in four rows of palisade setae, pubescence in median area forming a larger cluster of modified, shorter, thicker, and dense setae ( Fig. 38 )....... ephraim Kocian

12 Apical margin of male sternite VIII very broadly concave. Clusters of modified palisade and beard-like setae conspicuously separated from each other ( Fig. 36 ). Shape of large sclerites of internal sac of aedeagus in lateral view as in Fig. 27 .......................................................................................... nepalense (Scheerpeltz)

- Apical margin of male sternite VIII more shallowly and narrowly concave. Clusters of modified palisade and beard-like setae close to each other ( Figs 33, 34, 37 )..................................................................... 13

13 Clusters of modified palisade and beard-like setae on male sternite VIII larger, nearly as long as half of median length of sternite ( Fig. 37 ). Shapes of large internal sclerites of aedeagus in lateral view as in Fig. 26 ............... nepalicum (Coiffait)

- Clusters of modified palisade and beard-like setae on male sternite VIII smaller, much shorter than half of the length of sternite in the middle....................................................................................... 14

14 Smaller species, 3.41–4.8 mm, paramere only 0.24 mm long. Male sternite VIII in posterior part of median area with cluster of short, pointed, thickened, and dense setae ( Figs 22 , 33 ). Shapes of large internal sclerites of aedeagus in lateral view as in Figs 23 , 25 ...................................................................................... jumla sp. n.

- Larger species, 5 mm, paramere 0.29–0.30 mm long. Male sternite VIII in posterior part of median area with cluster of longer, thinner, and sparser setae as in Fig. 34 ...................................................... jaljalense (Coiffait)

Figures

FIGURES 25–31. Extruded internal sac of aedeagus from lateral view (25–27), apical portion of male sternite VII with position of dark long setae (28–30), apical portion of male sternite VIII (31). Ischnosoma jumla sp. n. (25), I. nepalicum (26), I. nepalense (27), I. quadriguttatum quadriguttatum (28), I. travei (29, 31), I. gratiosum (30). Scale bars: a (Figs 28–31), b (Figs 25–27).

FIGURES 12–14. Ischnosoma bhojpur sp. n. Male sternite VII (12); male sternite VIII (13); aedeagus in ventral (left) and lateral view (14). Scale bars: 0.1 mm: a (Figs 12–13), b (Fig. 14).

FIGURES 15–17. Ischnosoma hirthei sp. n. Male sternite VII (15); male sternite VIII (16); aedeagus in ventral (left) and lateral view (17). Scale bars: 0.1 mm: a (Figs 15–16), b (Fig. 17).

FIGURES 32–39. Male sternite VIII with position of dark setae, beard-like palisade setae and median dense setae, schematic. Ischnosoma iob (32), I. jumla sp. n. (33), I. jaljalense (34), I. fasciatocolle (35), I. nepalense (36), I. nepalicum (37), I. ephraim (38), I. thamar (39). Scale bar: 0.1 mm.

FIGURES 18–20. Ischnosoma schmidti sp. n. Male sternite VII (18); male sternite VIII (19); aedeagus in ventral (left) and lateral view (20). Scale bars: 0.1 mm: a (Figs 18–19), b (Fig. 20).

FIGURES 21–23. Ischnosoma jumla sp. n. Male sternite VII (21); male sternite VIII (22); aedeagus in ventral (left) and lateral view (23). Scale bars: 0.1 mm: a (Figs 21–22), b (Fig. 23).