Orthoceratium sabulosum (Becker, 1907)

Pollet, Marc & Stark, Andreas, 2018, The quest for the identity of Orthoceratiumlacustre (Scopoli, 1763) reveals centuries of misidentifications (Diptera, Dolichopodidae), ZooKeys 782, pp. 49-79 : 49

Orthoceratium sabulosum (Becker, 1907) Figs 1, 3 C–D, 4C, E, G, 5C, 6C, 8, 9, 10A

Alloeoneurus sabulosus Becker, 1907: 112. Type locality: Tunis (Tunisia) [ZMHB] - Alloeoneurus presumably synonymized with Orthoceratium by Kertész (1909)

Musca formosa Haliday, 1832: 356. Type locality: Cheshire (Great Britain) [unknown] syn. n.

Medeterus viridipes Macquart, 1834: 452. Type locality: Bordeaux (France) [unknown] syn. n.

Notes on synonyms.

Musca formosa Haliday, 1832 and Medeterus viridipes Macquart, 1834 were previously listed as synonyms of O. lacustre by Becker (1917). Our attempts to retrieve and examine the specimens proved unsuccessful (the latter specimen could not be located, Christoph Daugeron, pers. comm.). However, taking the position of their capture localities into account (see Figure 1), there is little doubt that they are conspecific to O. sabulosum .

Diagnosis. Rather large, short-bodied, rather slender (but stouter than O. lacustre ), brilliant green species with abdomen 1.3 × as long as thorax (Fig. 3 C–D). All legs mainly dark and metallic with narrowly yellow knees. Wing smokey reddish yellow, with reddish yellow veins (Figure 5C). Apical section of vein M1 with strong sinuous bend at ½. Posterior border of wing indented at vein CuA1. Coxa I with strong white pubescence, and with one strong curved black bristle at basal 1/3 and three black bristles at apex (Figs 3 C–D). Coxa II with one to three small black apical bristles on anterior face. Pedicel with strong apical bristles, with some ventral ones 1.5 × as long as pedicel is deep (Figure 5G). Ac uniseriate, rather strong, some about ½ × as long as dc. Male: face at least 1.4 × as wide as postpedicel is long (Figure 4C). Postpedicel with variable shape, at most as long as deep (Figure 4E). TV with tapering ventral process at each side baring coalescent bristles (Figure 10A). Femur I with large avoid brownish spot in basal 2/5, about 1/4 of femur length, covered with a conspicuous yellow pubescence (Figure 6C). Femora I–II bare ventrally. Tibia II with two ad bristles, rarely with 3rd much shorter basal bristle, and with two av bristles. Tibia III with two strong and two small pd bristles. Tarsus I with only one claw, and tarsomere taI1 with metallic reflection.

Redescription.

Male. Body length: 5.5-6.2 mm (n = 54); wing length: 5.2-6.1 mm (n = 77), 0.3 × as wide as long (n = 15) mm. Head (Fig. 4C, E, G). Face silvery white, rather parallel-sided, clypeus with triangular lower margin, strongly projecting; face 1.4-1.8 × as wide as postpedicel (length), with short white pubescence. Frons with metallic green ground colour, dusted yellowish white, less on posterior 1/2 in some specimens. Occiput brilliant metallic green, with weak dusting in some specimens, convex in middle. Palp about 1/4-1/3 of eye, trapezoid - elongate triangular, dark brown, dusted whitish, with white pubescence, and apical bristle absent. Proboscis dark brown. Eyes red, with short white pubescence. Uppermost eight-eleven postocular bristles bristles erect, black, and lower bristles curved, white, forming whiskers. One pair of black postocellar bristles. Antenna entirely dark brown, with scape bare, and pedicel with apical crown of strong bristles, with some ventral bristles about 1.5 × as long as pedicel is deep; postpedicel of rather variable shape, mostly rounded triangular, rarely rather subcircular, sometimes Hydrophorus -shaped, as long as deep, 0.7-0.8 × as long as scape and pedicel combined, with distinct pubescence; arista-like stylus dorsal, inserted at middle of upper rim of postpedicel, 2.3-2.7 × as long as first three antennal segments combined, bare. Thorax (Figure 3C). Mesonotum entirely brilliant metallic green with sometimes bluish violet tinge, strongly dusted greyish white on pleura and certain zones on dorsum, only without dusting between dc and ac, and between dc and npl areas; scutellum dark green to bluish green with violet tinge, bare on dorsum, with four marginal bristles, lateral pair much smaller than median pair. Anterior spiracle with group of multiple curved, yellowish white, long setae. Thoracic bristles black. Seven dc, with 1stdc laterally off-set, and 6-7thdc stronger; six to nine ac, uniseriate, reaching till 5thdc, rather strong, some about 1/2 × as long as dc; with two strong black, and one minute white ant pprn, one internal and one external bas pprn, one psut ial, one sut ial, two npl, two spal, and one pal bristles. Upper proepisternum with a large group of long yellowish white curved setae; lower proepisternum with one strong black curved bristle and a small group of yellowish white curved setae. Wing (Figure 5C). Slightly smokey reddish yellow, with reddish yellow veins. Vein R4+5 sinuous near wing apex, there parallel with vein M1; apical section of vein M1 with strong sinuous bend at ½ (MSSC); crossvein dm-cu slightly concave; posterior border of wing indented at vein CuA1. Proximal section of vein M1 2.0 × as long as apical section. Proximal section of vein CuA1 7.1 × as long as apical section. CuAx ratio: 1.6. Halter pale, calypteral fringe yellowish white. Legs (Figs 3C, 6C). Overall dark, metallic green, with pale yellow knees in all legs, and with black bristles. Coxae I–III dark, with metallic green ground colour, strongly dusted whitish, coxae I and III with extreme apex, and coxa II with less than apical 1/4 yellow. Coxa I with dense, white pubescence and one strong black curved bristle at basal 1/3, about 0.5 × as long as coxa I is long, and three strong, black ap bristles. Coxa II with dense white pubescence on anterior face, one inclined black bristle at 1/2, and one to three smaller black bristles at apex; lateral face bare. Coxa III with black, erect external bristle, inserted at 1/2, with vertical row of white setae. Trochanters dark brown. Femora I–III brilliant metallic green, femora I–II with pale yellow knee on apical 1/8, and on apical 1/10 in femur III. Femur I with large avoid brownish pv spot in basal 2/5, about 1/4 of femur length, covered with a conspicuous yellow pubescence (MSSC); with one rather small pv preapical bristle. Femur II with one strong ad bristle, at less than apical 1/5, and one small pv preapical bristle; with one row of short inclined pv setae along entire length, white on basal 2/3 and black on apical 1/3, longest at basis and apex. Femur III with one strong ad bristle, at about apical 1/3, and with one small pv preapical bristle; with one thin erect black ds bristle at about basal 1/5, nearly 0.5 × as long as femur is deep. Tibia I brilliant metallic green, and tibia I with basal 1/8, tibia II with basal 1/9, and tibia III with basal 1/10 pale yellow. Tibia I with two ds bristles, 2-3 × as long as tibia is deep; with two small ad bristles, 1-1.5 × as long as tibia is deep, and with three pv bristles, 2 × as long as tibia is deep; with white pilosity on av face along entire length, and with two small ap bristles. Tibia II with two ad bristles, 4 × as long as tibia is deep, rarely with 3rd much shorter basal bristle; with two pd bristles, about 2.5 × as long as tibia is deep, with basal bristle shorter, and with four ap bristles; with two av bristles, at basal 1/3 and 2/3, 2 × and 1.5 × as long as tibia is deep resp.; with one pv bristle, at basal 1/6, 2 × as long as tibia is deep, and two small pv bristles in apical 1/2, not as long as tibia is deep. Tibia III with five ad bristles, about 3 × as long as tibia is deep, two strong and two small pd bristles, former about 3.5 ×, latter 2 × as long as tibia is deep, and four strong ap bristles; with distinct pd row on apical 1/2; with four to five av bristles, 1.5 × as long as tibia is deep, and multiple shorter pv setae along entire length. Tarsi I–III black, with taI–III 1 with metallic green to bluish reflection and with multiple short black vt bristles, nearly as long as taI–III 1 is deep; taI5 with long curved dorsal setae at apex, 0.8 × as long as taI5 is long; only inner claw present (MSSC). Ratio of femur/tibia/tarsomeres 1-5 in leg I: 9/10/5.4/2.1/1.5/1/1.1, in leg II: 9/11/8/3.5/2.3/1.2/1, and in leg III: 9.8/13.8/6/4.2/2.6/1.3/1. Abdomen (Figure 3C). Basal five segments pubescent, 6th bare, minute, only visible dorsally; T brilliant metallic green, with bluish or with bronze tinge in some specimens, strongly dusted whitish on lower margins, with short dense black pubescence on dorsum, with long yellowish white setae laterally, strongest on sides of TI, and TI–V with black bristles on posterior margin, strongest on TI; TV brilliant metallic green with prominent dark bristles at posterior margin, with tapering ventral process at each side baring coalescent bristles (MSSC) (Figure 10A). ST with green ground colour and strong whitish dusting, with yellowish white, erect bristles. Hypopygium (Figures 8-9) with epandrium concolorous with tergites; hypandrium rather stout with subcircular apex, with ventrally curled up sides forming a gutter; phallus slender and strongly curved; two larger and one smaller basoventral epandrial setae, apicoventral epandrial lobe pale to reddish brown, stout, elongate ovoid and close to outer surstylar lobe; surstylus with robust pale to reddish brown outer (or dorsal) lobe with subcircular bristle at apex, inner (or ventral) surstylar lobe dark, robust with tapering apex baring a few bristles; postgonites robust, dark, with apical pubescence and a ds process; cercus dark brown, medium-sized, rather rectangular, with apex nearly bare. Female. Body length: 6.4-6.6 mm (n = 47); wing length: 5.2-6.5 mm (n = 65), 0.3 × as wide as long (n = 15). As male, except for: abdomen 1.4 × as long as thorax. Face 2.0-2.3 × (n = 5) as wide as postpedicel (length). Palp about 1/5-1/4 of eye, ovoid. Uppermost six to nine postocular bristles erect, black. One pair of postocellar bristles, rarely with two pairs. Pedicel with some ventral bristles longer than pedicel is deep; postpedicel 0.8-1.0 × as long as deep; arista-like stylus 2.4-2.7 × as long as first three antennal segments combined. Thorax with five to eight ac, reaching between 4th and 5thdc. Vein R4+5 bended but straight near wing apex, there parallel with vein M1; apical section of vein M1 with weak bend (sinuous) at 1/2; crossvein dm-cu rather straight. Proximal section of M 1.7 × as long as apical section. Proximal section of CuA1 6.5 × as long as apical section. CuAx ratio: 1.5. Femur I bare ventrally. Femur III with two to four thin erect black bristles in basal 1/5, about 1/3 × as long as femur is deep. Tibia II with two large ad bristles, and often 3rd shorter basal bristle. Tarsus III black, unmetallic, taI1 with multiple short black ventral bristles ventrally, nearly as long as taI1 is deep; taI5 with both claws. Ratio of femur/tibia/tarsomeres 1-5 in leg I: 8.5/9/5.3/2/1.5/1/1, in leg II: 9/10.5/7.8/3.2/1.9/1/1, and in leg III: 10.1/14.5/6.2/4.2/2.4/1.2/1. Abdomen with five pubescent segments, 6th invisible; also STIV with strong whitish dusting.

Type specimens examined.

LECTOTYPE (here designated to fix the identity of the species) ♂, TUNISIA: [Tunis governate] “Tunis904” / “Ujhelyi”, [bottom side] "X 26"; “Alloeoneurus” / "sabulosus Beck." / "det. Becker"; [red rectangular] “Lectotypus”; "Zool. Mus." / “Berlin” [ZMHB] (TN-01). PARALECTOTYPE ♀, TUNISIA: “Tunis904” / “Ujhelyi”, [bottom side] "XI 2"; [red rectangular] “Typus”; "Zool. Mus." / “Berlin” [ZMHB] (TN-01).

Notes on type material.

The original description of this species by Becker (1907) is based on multiple specimens (males and females) from Tunis, present in the HMNH at the time of the description. A holotype was not formally designated in Becker (1907) and it remains uncertain if the two specimens from the ZMHB were part of the type series. Fact is that both specimens in the ZMHB were collected by Ujhelyi in 1904 in Tunis, where Biró (HMNH) also collected Diptera in 1903 ( Horn et al. 1990). And as indicated by Becker (1906) all Tunis specimens were examined at the same time which led to the description of the species in 1907. It is thus very likely that the ZMHB specimens, indeed, belonged to the type series. As it remains uncertain who attached the existing lectotype and paralectotype lables to the ZMHB specimens and when, a formal designation is provided here. We have no explanation, though, how they ended up in Becker’s collection (ZMHB). The Becker catalogues at the ZMHB list a few specimens that he received as a gift from Biró, but these specimens always carry according labels (Jenny Pohl, pers. comm.). However, no such labels were found on the current lectotype and paralectotype.

Other material examined.

See Suppl. material 1. List of (non-type) records of Orthoceratium .

Distribution.

Compared to O. lacustre , O. sabulosum is much more widespread in the West Palaearctic and currently known with certainty from 14 countries, although it has not (yet) been collected in the northern part of the Mediterranean basin (see Figure 1): Denmark (South Jutland), Germany (Niedersachsen), Netherlands (Friesland, Zeeland, Zuid-Holland), Belgium (West-Vlaanderen), Great Britain (Cornwall, Dorset, Essex, Glamorganshire, Kent, Norfolk, North Somerset, Suffolk, Cheshire?), Ireland?, France (Morbihan, Gironde?), Portugal (Algarve, Beira Alta, Beira Litoral, Douro Litoral), Madeira?, Spain (Alicante, Cádiz, Córdoba, Segovia, Teruel, Zaragoza-Soria), Italy (Sardinia), Greece (Attica, North Aegean Islands), Algeria (Algiers, El Tarf, Oran), Tunisia (Ben Arous, Jendouba, Tunis), Turkey (inner Western Anatolia) and Iran (East Azerbaijan). Previous doubts about the occurrence of Orthoceratium in subsaharan Africa proved incorrect. However, specimens of O. lacustre identified and recorded by Grichanov (1997) from Tanzania, in fact, proved to belong to O. sabulosum (Figure 11). These records (see Appendix) from inland forest areas far beyond its West Palaearctic distribution range remain unexplained.

Ecology.

Based on the current records, the distribution range of O. sabulosum differs significantly from that of O. lacustre . Despite that, however, both species seem to display a surprisingly similar ecological amplitude. In northwestern Europe (from Great Britain over Belgium and the Netherlands to Germany and Denmark), it is confined to humid coastal habitats, with a strong preference for salt marshes and brackish marshes. In Belgium, the species has only been collected in sea-aster ( Aster tripolium ) vegetations, bordering shallow brackish to saltwater ponds ( Pollet et al. 2017) and in wet to slightly flooded Salicornia vegetations in brackish marshes and salt marshes (Pollet, unpubl. data). Also in Greece (Lesvos), Portugal (Algarve, Douro Litoral), Spain (Alicante) and north Africa (Algeria, Tunisia), records originate from locations close to the sea. In sharp contrast, the species is also known from locations between 700 m and 1,907 m in Portugal, Spain, Turkey and Iran, mostly in (coniferous) forest habitat and often with or close to small streams or open water (lakes).