Chersodromia nubifera Coquillett
Creators: name: Maeda, Takuya
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Hybotidae
Chersodromia
Chersodromia nubifera

description: Chersodromia nubifera (Coquillett)
(Figs. 9, 12, 16, 19, 41–49)
Tachydromia nubifera Coquillett, 1899: 343; Melander, 1902: 342; Aldrich, 1905: 313.
Coloboneura nubifera (Coquillett): Coquillett, 1903: 265; Melander, 1910: 52, 1928: 294, 1945: 81, 82; Curran, 1931: 11 (in key).
Tachista nubifera (Coquillett): Kertész, 1909: 142.
Chersodromia kamtchatkiana Chvála, 1970: 388 –390, figs. 6–8; Chvála, 1978: 71 –73, figs. 10–12; Shamshev, 2001: 278 (in key). syn. nov.
Chersodromia nubifera (Coquillett): Chvála, 1970: 390, fig. 9; 1978: 74; Shamshev, 2001: 278 (in key).
Diagnosis. A large, black species measuring more than 2.5 mm, with wide gena. Stylus long. Polished area on katepisternum small. Vein R1 meeting costa after midway of wing. Fore tibia swollen, with distinct gland. Male terminalia heavily sclerotized with right surstylus composed of 3 distinct lobes and large, spatulate left cercus. Long, black vertical setae (2 pairs) and supra-alar setae present; posthumeral setae absent. Hind femur with anteroventral row of somewhat erect setae mainly in apical half.
Description. Male (Fig. 9). Body length 2.55–2.85 mm; head width 0.43–0.52; wing length 2.55–2.75 mm. Head (Fig. 41) black in ground-colour and greyish pollinose; palpus brown in ground-colour and greyish pollinose; proboscis brown, slightly shining; antenna dark brown; all setae and setulae on head black. Frons relatively narrow; in frontal view face below antennal sockets wider than frons. Ocellar setae (2 pairs) moderate in length, as long as scape, pedicel and postpedicel combined. Vertical setae (2 pairs) longer than ocellar setae. In frontal view gena very wide, 1/2.5 as wide as maximum eye height. Occiput with setulae (some on its lateral side long). Antenna (Fig. 42): postpedicel round in lateral view, bearing brown setulae on anterior margin; extension of postpedicel present dorsoapically; stylus long, ca. 2.5 times as long as pedicel and postpedicel combined. Palpus sparsely covered with ca. 15 setulae (apical one longest) and sensory pit visible without preparation in wet specimens.
Thorax (Fig. 43) black in ground-colour, greyish pollinose; all setae and setulae black. Katepisternum with small polished area. Vestiture on thorax: 2–3 setulae on each proepisternum; 1 pair of long, inflected postpronotal setae; no posthumeral setae; 4–5 pairs of notopleural setae; 1 pair of supra-alar setae; 1 pair of long postalar setae; 2–3 pairs of dorsocentral setae in rows near median line; many dorsocentral setulae in multiple rows; 1 pair of incomplete rows of acrostichal setulae; 1 pair of inflected apically scutellar setae; 1 pair of tiny subapical scutellar setulae.
Wing (Fig. 16) normally developed, somewhat narrow and entirely clear with grey tinge on anterior part, with pale brown veins. Basicosta with 1 or 2 dark brown setae and some black setulae; costa with small, brown setulae along anterior margin, ending at connection with vein M1+2; subcosta absent; R1 meeting costa after midway of wing; radial sector moderate in length; CuA1 connected to wing margin; anal vein reduced to pale, fold-like line. Calypter whitish with brown tinge. Halter brown, partially whitish.
Legs stout, dark brown; all setae and setulae on legs black. Fore femur covered with short setulae except on ventral surface, with 1 anterior seta, anteroventral row of 12–17 long setulae, strong preapical setulae (1 posterodorsal preapical, 1 posterior preapical, 1 or 2 posteroventral), posteroventral row of long setulae and long, dense whitish microtrichia on ventral surface. Fore tibia swollen in dorsal view, covered with setulae (especially dense on anterior surface), with 1 anteroventral preapical seta and 1 posteroventral preapical seta, posteroventral row of curved setulae, and whitish microtrichia on ventral surface. Fore tibial gland distinct (Fig. 19). Mid femur covered with setulae, with anteroventral row of ca. 15 tiny, black spinulae, 1 anterior seta, posteroventral row of strong setulae mainly in apical half. Mid tibia covered with setulae, with anteroventral row of many short, black spinulae (distances between adjoining spinulae very close to one another, with row appearing as comb), 3–4 anterior setae near base, 1 anterior preapical seta, 1 anterodorsal seta, 1 anteroventral preapical seta, 1 posteroventral preapical seta and 1 posterior seta. Hind femur densely covered with setulae, with 1 ventral seta near base, anteroventral row of 3–6 somewhat erect setae mainly in apical half and 1 anterior seta near apex. Hind tibia covered with setulae (strong, short setulae present on ventral surface mainly in apical half), with anteroventral row of 5 setae, 1 anterior preapical seta, anterior row of 5 setae, 2 anterodorsal preapical setae, anterodorsal row of 4 setae, dorsal row of 4 setae and 1 ventral preapical seta. Fore, mid and hind tarsomeres densely covered with setulae, fore and mid tarsomeres greyish pollinose.
Preabdomen covered with dark brown setulae; tergites and sternites dark brown in ground-colour, sparsely whitish pollinose; membrane pale brown in ground-colour, sparsely whitish pollinose. Tergites 1–7 each with 2 plaques laterally and 1 pair of small shiny pits dorsolaterally. Tergite 7 with many setae along posterior margin. Eighth segment hidden, with many setae along posterior margin.
Terminalia (Figs. 44–48). Coloration: right epandrial lamella dark brown in ground-colour and greyish pollinose; right cercus shiny light brown; left cercus shiny black; left surstylus shiny black/brown; left epandrial lamella and hypandrium dark brown. Right surstylus composed of 3 lobes with distinct boundary line between right epandrial lamella in both dry and wet specimens (Figs. 44, 47); apical lobe shiny black, elongate with round tip (Fig. 44); median lobe shiny pale brown, flattened with 2 long setulae at apex (Figs. 44, 47); basalmost lobe shiny brown, flattened (Fig. 47). Right epandrial lamella with dark brown setae. Left surstylus consisting of several lobes; outermost lobe small, trifurcate, tip of median projection rounded (Fig. 46). Right cercus small, sclerotized (Fig. 48); left cercus conspicuously large, heavily sclerotized and spatulate (Fig. 45), with apical setae.
Female. Body length 2.43–2.50 mm; head width 0.48–0.50 mm; wing length 2.60–2.66 mm. Resembling males except in structures of fore and mid legs and terminalia. Fore tibia more slender than in males, without posteroventral row of curved setulae. Mid femur without anteroventral row of spinulae (but alternative row of long setulae present). Mid tibia without anteroventral row of spinulae. Cercus brown.
Material examined. The above description is not based on the type material (Commander Is.) but specimens collected in the southern part of Primorsk Territory. Specimens examined here are deposited in IBSS, USNM, OUMNH and TMC.
Dried specimens: 20 3, 20 Ƥ, S. Primorye, Gamov Pen., Astaf’ev Bay (bare sands), 26.viii.2010. Alcohol specimens: 6 3, 7 Ƥ, S. Primorye, Gamov Pen., Astaf’ev Bay (bare sands), 26.viii.2010; 3 3, 1 Ƥ, same loc. (scrub zone), 26.viii.2010; 1 3, 1 Ƥ, Gamov Pen., Vityaz’ Bay, 23.viii.2010; 2 Ƥ, same loc., 24.viii.2010; 24 3, 44 Ƥ, Nazimov Cape, 28.viii.2010.
Type material. 1 3, 2 Ƥ syntypes of C. nubifera labelled: Bering island, L. Stejinger coll., vi-viii. 1897; USNM-2054080. The male is here designated as the lectotype and the two females as the paralectotypes.
Paratypes of C. kamtchatkiana (OUMNH-2007-060): 1 3 and 1 individual (abdomen missing) labelled: Bolscherjetsk, Kamtschatka, Y. Wuorentaus coll., 19.viii.1917.
Distribution. Russian Far East: Primorsk Territory (new record), Kamchatka Peninsula and Commander Islands.
Remarks. In the present survey, this species was not collected on the shores along bays. The adults were quite abundant on sandy shores facing the open sea (Figs. 3, 5), running about on washed up debris, comprised mainly of seaweeds.
Chersodromia kamtchatkiana is herein considered a junior synonym of C. nubifera. Coquillett (1899) described C. nubifera, based on three specimens (syntypes), one male and two females. Later C. nubifera was redescribed by Chvála (1970), and provided an illustration of the male syntype (Chvála 1970, fig. 9) drawn by a curator working in the museum it was deposited in. When the same male syntype was observed (Fig. 12), I found an error in the illustration of the terminalia. The structure of the left surstylus in Chvála’s illustration differs from that of the syntype specimen, probably because the artist misunderstood the configuration of some parts in particular the outermost lobe and inner lobes. Since the difference is slight but important for identification, the structure is redrawn (Fig. 49). The terminalia are actually similar to those of C. kamtchatkiana given in papers by Chvála (1970, 1978) except in the structure of right epandrial lamella. Finally after examining a paratype of C. kamtchatkiana, it is clearly conspecific with C. nubifera, on the basis of the structure of the right surstylus. In Chvála (1970), the drawing is from an angle where the basalmost lobe of the right epandrial lamella cannot be observed.
Although Chvála (1970) mentioned differences in wing venation and size of the polished area on the katepisternum between C. kamtchatkiana and C. nubifera, I consider these differences are due to variation within C. nubifera.
An undescribed species from Hokkaido, Japan (Saigusa 2008) is probably C. nubifera because the diagnostic characters of the former are very similar to those of C. nubifera.
description: Published as part of Maeda, Takuya, 2011, New species of Chersodromia from the Russian Far East (Diptera: Empidoidea: Hybotidae: Tachydromiinae), pp. 1-24 in Zootaxa 2979 on pages 14-17, DOI: 10.5281/zenodo.202911