Ischnosoma convergens, Assing, 2019

Assing, Volker, 2019, New species and additional records of Ischnosoma from Georgia (Coleoptera, Staphylinidae, Tachyporinae), Linzer biologische Beiträge 51 (2), pp. 773-788 : 785-786

Ischnosoma convergens nov.sp. ( Figs 3-4 , 32-34, 40-42 , Map 3 )

T y p e m a t e r i a l: Holotype ♂: " GEORGIA [40] - Adjara, NE Batumi, Mtirala National Park , 41°40'36''N, 41°52'23''E, 300 m, 18.VII.2019, V. Assing / Holotypus ♂ Ischnosoma convergens sp. n. det. V. Assing 2019" (cAss) . Paratypes: 1♀: same data as holotype (cAss) ; 1♀: same data as holotype, but leg. Schülke ( MNB) ; 1♂, 1♀: same data as holotype, but "[40a]" (cAss) ; 6♂♂, 1♀ [partly slightly teneral]: " N41°40'47 E41°42'19, GG Adjara Chakvistavi , 330 m 17.5.2019, Brachat & Meybohm (19)" (cAss) ; 1♀: "N 41°41'27 E 41°49'48, GG Adjara Chakvistavi W, 150 m 18.5.2019, Brachat & Meybohm (20)" (cAss) ; 1♂: " N41°40'34 E41°52'49, GG Adjara Chakvistavi E, 360 m 20.5.2019, Brachat & Meybohm (27)" (cAss) ; 1♂: " N41°39'12 E41°45'36 (9), Georgien Adjara, Batumi 7 km NE, 500-600 m, Brachat & Meybohm 24.6.2017 " (cAss) ; 1♂: " N41°41'21 E41°43'50, Georgien Adjara (59), Chakvistavi , 170 m, 22.5.2018, Brachat & Meybohm" (cAss) ; 1♀: " 41°30'38 E 41°52'37, Georgien Adjara (60), Chikuneti E 580 m, 23.5.2018, Brachat & Meybohm" (cAss) .

E t y m o l o g y: The specific epithet (Latin, adjective) alludes to the distinctly converging apico-lateral lamellae of the median lobe of the aedeagus, one of the characters distinguishing this species from the highly similar I. parallelum .

D e s c r i p t i o n: Very small species of slender habitus, body length 2.5-3.3 mm; length of forebody 1.2-1.4 mm. Habitus as in Fig. 3 . Eye rudiments ( Fig. 4 ) minute, approximately as large as antennomere I in cross-section, composed of 0-5 ommatidia, often with additional degenerated rudiments of ommatidia. Pronotum approximately 1.15 times as broad as long and 1.6 times as broad as head. Other external characters similar to those of I. myops .

♂: shape and chaetotaxy of sternite VII unmodified ( Fig. 40 ); sternite VIII ( Fig. 41 ) with sparse unmodified pubescence, posterior margin weakly concave; median lobe of aedeagus ( Figs 32-34 , 42 ) 0.42-0.45 mm long (0.50-0.54 mm including parameres); ventral process apically broadly convex in ventral view and obtuse in lateral view; apicolateral lamellae distinctly converging apicad; internal sac with a pair of short and broad apical and a pair of small and curved median sclerites, and with small and dark basal membranous structures.

C o m p a r a t i v e n o t e s: Ischnosoma convergens is distinguished from the similar I. myops only by smaller size ( I. myops : length of forebody 1.4-1.7 mm), a more slender habitus ( I. myops : pronotum approximately 1.2 times as broad as long and 1.7 times as broad as head), smaller eye rudiments ( I. myops : eyes significantly larger than antennomere I in cross-section), a posteriorly weakly concave male sternite VIII ( I. myops : posterior margin truncate), and a smaller aedeagus ( I. myops : aedeagus approximately 0.5 mm long, 0.6 mm including parameres) with a ventral process and internal structures of different shapes. The new species is readily distinguished from all other Caucasian representatives of the genus, except the following species, by much smaller size and smaller eye rudiments alone. For illustrations of I. myops see Figs 7-8 , 38-39, 46.

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: Based on currently available data, I. convergens is endemic to Mtirala National Park and its vicinity in the extreme west of the Meskheti Range, Adjara region, Southwest Georgia ( Map 3 ). The male paratype collected in 2017 was reported as I. myops in ASSING & SCHÜLKE (2017). The specimens were mostly sifted from litter in moist deciduous forests, often with rhododendron undergrowth; few specimens were collected by soil-washing. The altitudes range from 150 to approximately 600 m. In some localities, the species was collected together with I. myops and/or I. molle . Some of the type specimens collected in May are more or less distinctly teneral.

Figures

Map 3: Distributions of Ischnosoma convergens (black circles) and I. parallelum (white circles).

Figs 1-8: Ischnosoma acre (1), I. cuspidatum (2), I. convergens (3-4), I. parallelum (5-6), and I. myops (7-8): (1-3, 5, 7) habitus; (4, 6, 8) head and pronotum in lateral view. Scale bars: 1-3, 5, 7: 1.0 mm; 4, 6, 8: 0.5 mm.

Figs 40-46: Ischnosoma convergens (40-42), I. parallelum (43-45), and I. myops (46): (40, 43) male sternite VII; (41, 44, 46) male sternite VIII; (42, 45) apical portion of median lobe of aedeagus in ventral view. Scale bars: 40-41, 43-44, 46: 0.2 mm; 42, 45: 0.1 mm.

Figs 32-39: Ischnosoma convergens (32-34), I. parallelum (35-37), and I. myops (38-39): aedeagus in lateral and in ventral view. Scale bar: 1.0 mm.