Musca formosa Haliday, 1832 and Medeterus viridipes Macquart, 1834, previously listed as synonyms of O. lacustre, clearly refer to O. sabulosum (see further).

Large, short-bodied, slender, entirely green species with abdomen 1.6 × as long as thorax (Figs 2, 3A, B). All legs mainly dark and metallic with narrowly yellow knees. Wing smokey reddish yellow, with reddish yellow veins (Fig. 5A, B). Apical section of vein M₁ with strong sinous bend at ½. Posterior border of wing indented at vein CuA₁. Coxa I with strong white pubescence, and with three black bristles only at apex. Coxa II with only pale bristles at apex anteriorly. Pedicel with short apical bristles (Figure 4F). Ac uniseriate, rather small, at most 1/3 as long as dc. Male: face not as wide as postpedicel is long (Figure 4A). Postpedicel elongate triangular, at least 1.2 × as long as deep (Figure 4D). T_V with blunt ventral process at each side bearing short dark separate bristles (Figure 10B). Femur I with small ovoid brownish yellow pv tuft just beyond basal 1/4, about 1/8 of femur length (Figure 6A). Femora I–II with multiple rows of very short white erect setae on basal ½. Tibia II with three ad bristles, with basal bristle shorter, and with one av bristle. Tibia III with four strong and one small pd bristles. Tarsus I with only one claw, and tarsomere taI₁ mostly unmetallic (Figure 6B).

Figure 3. 

Orthoceratium lacustre, habitus (W): A male B female. Orthoceratium sabulosum, habitus: C male D female. Same scale in all pictures.

Figure 4. 

Orthoceratium lacustre, head: A face (male) B face (female) D antenna (male) F pedicel, posterior view (male). Orthoceratium sabulosum, head: C face (male) E antenna (male) G pedicel, posterior view (male).

Figure 5. 

Orthoceratium lacustre, wing and halter: A male B female. Orthoceratium sabulosum: C wing (male). Veins R₄₊₅, M₁, CuA₁, and dm-cu indicated.

Figure 6. 

Orthoceratium lacustre, male: A femur I (posteroventral view) B tarsomere I₅, with left tarsus on the left and right tarsus on the right hand side (dorsal view). Orthoceratium sabulosum, male: C femur I (posteroventral view).

Male. Body length: 5.0–5.7 mm (n = 25); wing length: 5.2–6.2 mm (n = 44), 0.3 × as wide as long. Head (Fig. 4A, B, D, F). Face silvery white, slightly narrowing towards middle of face, then widening towards clypeus, latter with triangular lower margin, weakly projecting; face 0.9 × as wide as postpedicel (length), with short white pubescence. Frons with metallic green ground colour, strongly dusted yellowish white. Occiput with metallic green ground colour, dusted whitish, convex in middle. Palp 1/5–1/4 of eye, triangular, dark brown, strongly dusted whitish, with white pubescence, and apical bristle absent. Proboscis dark brown. Eyes red, with short white pubescence. Uppermost seven to nine postocular 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 short bristles; postpedicel dark brown, elongate triangular, with blunt apex, 1.2–1.4 × as long as deep, 0.9–1.3 × as long as scape and pedicel combined, with short pubescence; arista-like stylus dorsal, inserted at middle of upper rim of postpedicel, 2.0–2.4 × as long as first three antennal segments combined, bare. Thorax (Figs 2, 3A). 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 bluish violet, 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 1^stdc laterally off-set, and 6–7^thdc stronger; three to five ac, uniseriate, reaching level between 5^th and 6^thdc, rather small, at most 1/3 × 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 5A). 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 sinous bend at ½ (MSSC); crossvein dm-cu rather straight; posterior border of wing indented at vein CuA₁. Proximal section of vein M₁ 1.9 × as long as apical section. Proximal section of vein CuA₁ 8.5 × as long as apical section. CuA_x ratio: 1.7. Halter pale, calypteral fringe yellowish white. Legs (Figs 2, 3A, 6A–B). Overall dark, metallic green to violet, with pale yellow knees in all legs, and with black bristles. Coxae dark, with metallic green ground colour and strongly dusted whitish, coxae I–II with about apical 1/4 yellow, coxa III with about apical 1/3 yellow. Coxa I with dense, white pubescence and three rather small, black ap bristles. Coxa II with dense white pubescence on anterior face, and one black inclined bristle at 1/2 on margin; lateral face bare. Coxa III with one black, erect external bristle, inserted at 1/2, with vertical row of white setae. Trochanters dark brown. Femora I–III brilliant metallic green, sometimes with violet tinge, femora I–II with pale yellow knee on apical 1/8, and on apical 1/10 in femur III. Femur I with multiple rows of very short white erect setae on basal ½ (MSSC); with small ovoid brownish yellow pv tuft just beyond basal 1/4, about 1/8 of femur length (MSSC); with one rather small pv preapical bristle. Femur II with one strong ad preapical bristle, at less than apical 1/5, and with one small pv preapical bristle; with one row of very short white erect vt setae on basal 1/3 (MSSC), and 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 preapical bristle, at about apical 1/3, and one small pv preapical bristle; sometimes with some thin inclined (thus not erect!) ds bristles in basal 1/5. Tibiae I–III brilliant metallic green to violet, tibia I with basal 1/8, tibia II with basal 1/9, and tibia III with less than 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 two to three pv bristles, 2–3 × as long as tibia is deep; with white pilosity on av face along entire length, and with two small ap bristles. Tibia II with three ad bristles, about 3 × as long as tibia is deep, with basal bristle shorter; with two pd bristles, 2 × as long as tibia is deep, with basal bristle shorter, and with four ap bristles; with one av bristle at basal 2/3 and one pv bristle at basal 1/5, both 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 2.5 × as long as tibia is deep, four strong and one small pd bristles, former about 2.5 x, latter not as long as tibia is deep, and four strong ap bristles; with distinct pd row on apical 1/2; with three-four av bristles, 1–1.5 × as long as tibia is deep, and with multiple shorter pv setae along entire length. Tarsi I–III dark brown, with taI₁ mostly unmetallic and taII₁ and taIII₁ with metallic green to violet reflection. Tarsus I with taI₁ with pale ventral pubescence (MSSC) with some darker short bristles; taI₅ with long curved dorsal setae at apex, 0.7 × as long as taI₅ length; only inner claw present (MSSC). Tarsus II with taII₁ with multiple short vt bristles, nearly as long as taII₁ is deep. Tarsus III with taIII₁ with multiple inclined vt bristles, longest about as long as taIII₁ is deep. Ratio of femur/tibia/tarsomeres 1–5 in leg I: 10.3/11.4/6.3/2.2/1.5/1/1.1, in leg II: 9.5/12.2/8.4/3.7/2.4/1.3/1, and in leg III: 10.6/15.3/6.7/4.6/2.8/1.4/1. Abdomen (Figure 2, 3A). Basal five segments pubescent, 6^th 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, long yellowish white setae laterally, strongest on sides of T_I, and T_I–IV with black bristles on posterior margin, strongest on T_I; T_V brilliant metallic green without prominent dark bristles on posterior margin, with blunt ventral process at each side, with short dark separate bristles (MSSC) (Figure 10B). ST with green ground colour, strongly dusted whitish, with yellowish white, erect bristles. Hypopygium (Figure 7) with epandrium concolorous with tergites; hypandrium rather stout with subcircular apex, with ventrally curled up sides forming a gutter; phallus slender and strongly curved; three basoventral epandrial setae of subequal size, and apicoventral epandrial lobe pale reddish yellow, stout, narrowing towards apex and adjacent to outer surstylar lobe; surstylus with robust pale reddish yellow outer (or dorsal) lobe with area of minute spines near apex and 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 vt process; cercus dark brown, medium-sized, rather rectangular, apex large subcircular, with dense yellow pubescence, dark brown. Female (Figure 3B). Body length: 5.4–6.2 mm (n = 23); wing length: 5.2–6.7 mm (n = 51), 0.3 × as wide as long. As male, except for: abdomen 1.4 × as long as thorax, slender. Face 1.7–2.3 × as wide as postpedicel (length). Frons ground colour metallic green, strongly dusted yellowish white. Palp ovoid. Uppermost eight to ten postocular bristles black. Antenna dark brown, with scape sometimes paler (yellowish brown); postpedicel triangular, with blunt apex, 0.9–1.1 × as long as deep, 0.8–0.9 × as long as scape and pedicel combined; arista-like stylus 2.4–2.7 × as long as first three antennal segments combined. Thorax with four to five ac, reaching between 4^th or 5^thdc. Wing (Figure 5B) with 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 straight. Proximal section of M 1.7 × as long as apical section. Proximal section of CuA₁ 6.9 × as long as apical section. CuA_x ratio: 1.6. Coxa I with two to three rather small, black ap bristles. Femur I bare ventrally. Femur III often with some thin inclined ds bristles in basal 1/5. Tibiae I–II with basal 1/10 pale yellow; tibia I with three pv bristles. Tibia II with two av bristles at basal 2/5 and 2/3, 2–2.5 × as long as tibia is deep, and four small pv bristles on entirely length, not as long as tibia is deep. Tibia III with ad bristles about 3 × as long as tibia is deep, and with four strong pd bristles, 2.5–4 × as long as tibia is deep. Tibia III with av bristles 1.5–2.0 × as long as tibia is deep. Tarsus I with taI₁ with multiple short black ventral bristles, nearly as long as taI₁ is deep; taI₅ with both claws. Ratio of femur/tibia/tarsomeres 1–5 in leg I: 8.6/9.5/5.7/2.3/1.5/1/1.1, in leg II: 9.1/11.6/8.1/3.4/2/1.2/1, and in leg III: 10.6/15/6.4/4.3/2.6/1.4/1. Abdomen with five pubescent segments, 6^th invisible; also ST_IV with strong whitish dusting.

Figure 7. 

Orthoceratium lacustre, hypopygium: A left lateral view B ventral view. Abbreviations: hyp: hypandrium, ph: phallus, bv eps: basoventral epandrial setae, apv epl: apicoventral epandrial lobe, dsur: dorsal surstylar lobe, pgo: postgonites, cerc: cercus. Scale bars: 0.1 mm.

ITALY: NEOTYPE (here designated to fix the identity of the species) ♂, [brownish rectangular] “Liancalus/ lacustris Scp”/ “Görz.” [= Gorizia, in Friuli-Venezia Giulia region]; “Zool. Mus.”/ “Berlin”; “Orthoceratium lacustre”/ “(Scopoli, 1763)”/ “det. Marc Pollet, 2017”; [red rectangular] “NEOTYPE” / “des. Marc Pollet, 2018” (2017 on initial label in Figure 1) [ZMHB] (IT-04).

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

In order to fix the identity of the species, a neotype of O. lacustre was selected on the basis of the locality (closest to the original type locality or region), and the preservation status of the specimen (see Figure 2).

Of all examined specimens (n = 131) one Trieste specimen featured a strong curved black bristle on the right fore coxa.

As a result of the taxonomic mix-up between both species in the past, previous distribution records of O. lacustre in the literature – many of which refer to O. sabulosum in reality – must be considered unreliable. Our present study revealed that O. lacustre has been collected nearly exclusively along the northern border of the Mediterranean basin (incl. adjacent islands), both in coastal habitats and inland (montane) habitats (see Figure 1). Its current distribution range includes: France (depts Hérault, Var, Bouches-du-Rhône, Gard), Italy (Sardinia, Gorizia, Livorno, Syracuse, Taranto, Veneto), Slovenia (see Scopoli 1763), Montenegro (Central Region), Croatia (Dubrovnik-Neretva Co.), Greece (Ionian and North Aegean Islands, Serres, Thessaloniki, Trikala), Bulgaria (Burgas), and Algeria (Oran). Its range overlaps with that of O. sabulosum only in Oran (Algeria), and on the islands of Sardinia (Italy) and Lesvos (Greece). In the latter site, both species have been collected (in different years by different collectors) in the same area.

Previous records from Austria, Ireland, Madeira or Crimea (Ukraine) could not be verified due to a lack of specimens, but it is very likely that the Irish and Madeiran records refer to O. sabulosum (see Figure 1).

With only two clear exceptions, O. lacustre has been recorded from mostly lowland locations in a 25 km zone along the Mediterranean coast, where it seems to occur along inland lakes which also corresponds with the description of the habitat of the type specimens (Scopoli 1763). Only on Sardinia (at 480m) and in Greece (prov. Serres) has the species been collected in habitats less or not affected by the sea. At the two Greek sites, both above 1,100m, and presumably also in Sardinia, the species occurred along small streams in mixed forest (beech and spruce forest in Greece).

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. 3C–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 3C–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). T_V 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 3^rd 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.

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 1^stdc laterally off-set, and 6–7^thdc stronger; six to nine ac, uniseriate, reaching till 5^thdc, 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. CuA_x 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 3^rd 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–III₁ with metallic green to bluish reflection and with multiple short black vt bristles, nearly as long as taI–III₁ 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, 6^th 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 T_I, and T_I–V with black bristles on posterior margin, strongest on T_I; T_V 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 4^th and 5^thdc. 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. CuA_x 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 3^rd 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, 6^th invisible; also ST_IV with strong whitish dusting.

Figure 8. 

Orthoceratium sabulosum, hypopygium (left lateral view). Abbreviations: hyp: hypandrium, ph: phallus, bv eps: basoventral epandrial setae, apv epl: apicoventral epandrial lobe, dsur: dorsal surstylar lobe, pgo: postgonites, cerc: cercus. Scale bar: 0.1 mm.

Figure 9. 

Orthoceratium sabulosum, hypopygial appendages: A hypandrium (hyp), phallus (ph) and postgonites (pgo) (right lateral view) B apicoventral epandrial lobe (apv epl), dorsal (dsur) and ventral surstylar lobes (vsur) (inner view of left surstylus). Scale bar 0.1 mm (applicable for A, B).

Figure 10. 

Posteroventral process on 5^th tergite, male: A O. sabulosum B Orthoceratium lacustre. Scale bars: 0.5 mm (tergites) and 0.1 mm (processes).

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).

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.

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

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.

Figure 11. 

Orthoceratium sabulosum from Kimboza Forest Reserve, Tanzania: A male specimen B labels (photos by Zoltán Soltész).

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).