Swammerdamella gracilis, Xiao & Hong & Li & Yang, 2025

Xiao, Yishen, Hong, Dawei, Li, Zhu & Yang, Ding, 2025, First report of the genus Swammerdamella Enderlein, 1912 (Diptera: Scatopsidae) in China, with descriptions of nine new species, Zootaxa 5723 (1), pp. 49-70 : 55-57

6. Swammerdamella gracilis sp. nov. DZAEDzĸxü

( Figs. 3A–3F )

Diagnosis. M fork shorter than stem with M 1 and M 2 close to each other. Male sternite 6 unmodified, posteriorly with a row of setae. Posterior margin of male tergite 7 modified and with a triangular projection. Aedeagus plate sclerotised. Aedeagus long and thin.

Description. Male ( Fig. 3A ). Body length 1.6–2.0 mm, wing length 1.3–1.5 mm.

Head. Dull brown, slightly higher than long; antennae 10-segmented and relatively slender; flagellum 8- segmented, each flagellomere with a whorl of microtrichia; last flagellomere distinctly elongate, twice as long as preceding one; eyes holoptic; palpus one-segmented, brown, and pointed at apex.

Thorax. Dull brown, stout and shining; scutum short yellowish brown pilose.Anterior spiracular sclerite obvious and triangular. Halters darker than scutum, with several setae on stem. Legs short, concolorous with body; tarsus and apical part of hind tibia yellowish brown.

Wing ( Fig. 3B ). Membrane nearly hyaline; anterior veins sclerotised and yellowish brown, R 1 and R 4+5 short, joining costa vein very close to each other; M fork complete and narrow, shorter than stem; CuA sigmoid, bent smoothly towards posterior margin; a row of black microtrichia present on posterior margin of wing.

Abdomen. Strong and dull brown; segments 1–6 visible; sternite 6 ( Fig. 3C ) densely setose, posterior margin unmodified and with a row of setae; tergite 6 ( Fig. 3D ) densely setose, posterior margin with an obvious, triangular projection with its margin sclerotised. Segment 7 ( Fig. 3F ) retracted into segment 6; tergite 7 thick, folded, with both arms densely setose, ventral process long and rectangular; sternite 7 rounded in general shape, both arms setose, with a highly sclerotised median concavity on inner margin.

Male terminalia ( Fig. 3E ). Longer than wide; aedeagus plate highly sclerotised and circular concave; aedeagus long and slender, swollen apically. Both sides of aedeagus plate with 2 oval, setose projections.

Female. Unknown.

Type Material. HOLOTYPE: ♂, China, Hubei Province, Shennongjia Forestry District [ öṝĕū区], Dajiuhu [ 大九ª] [ 31°28’ N, 110°1’ E, 1767m], collected by sweep net, 2023. VI. 19, Xingnong Xu ( CAU) . PARATYPES: 1♂ 3♀, same data as holotype .

Other Material. 2♂ 2♀, China, Heilongjiang Province, Heihe [ Dzñ], Pingshan Tree Farm [ ṮƜū场] [ 49°34’N, 126°56’ E, 302m], collected by sweep net, 2024. VII. 6, Yuetian Gao ( CAU) ; 4♂ 3♀, China, Heilongjiang Province, Heihe [ Dzñ], Pingshan Tree Farm [ ṮƜū场] [ 49°34’ N, 126°56’ E, 302m], collected by sweep net, 2024. VII. 6, Xingnong Xu ( CAU) .

Distribution. China ( Heilongjiang Province; Hubei Province).

Etymology. This specific name is derived from the Latin adjective “gracilis ”, which means “slender” or “thin”, referring to the shape of aedeagus.

Remarks. S. gracilis has distinctive morphological characters that differ from all known Swammerdamella species, and the general shape of male terminalia is a bit similar to the North American species S. confusa Cook, 1956 . Surprisingly, this species has a wide distribution among China and was discovered from 31°27’ N to 50°7’ N, across the Oriental and the Palaearctic Regions. It can be easily recognized by sclerotized aedeagus plate and a remarkably long aedeagus. Segment 7 of male is also highly sclerotized and densely setose.

Figures

FIGURE 3A–3B. 3A. Swammerdamella gracilis sp. nov., male adult. 3B. Wing. 3C. Male sternite 6. 3D. Male tergite 6. 3E. Male terminalia. 3F. Male segment 7. Scale bar 1.0 mm (3A–3B), 0.1 mm (3C–3F).