Dolichopus nimbatus Parent

Dolichopus nimbatus Parent

Dolichopus nimbatus Parent, 1927: 454.

Dolichopus thalhammeri Knézy, 1929: 19 syn. nov. Dolichopus balius Meuffels, 1981: 327 syn. nov.

Notes on synonymy. In order to establish if all species were conspecific, the female paratype of D. balius was first compared to the female holotype of D. nimbatus. Subsequently, features listed in the original description of the lost D. thalhammeri were checked in a male paratype of D. balius. All specimens were examined thoroughly.

All differences between the female holotype of D. nimbatus and female paratype of D. balius were within the range of intraspecific variability and all important diagnostic features were identical or very comparable in both specimens. Also, the male paratype of D. balius entirely matched the characters described by Knézy (1929) for the male of D. thalhammeri, except for some minor discrepancies in the chaetotaxy of the legs. The latter, however, could be explained as the mere result of a slightly different interpretation of character states by the respective authors, and/or of a slightly different accuracy. Both males also shared the important diagnostic features listed below. It could therefore be concluded that D. nimbatus, D. balius and D. thalhammeri are conspecific.

Diagnosis (both sexes). Wing (Figs 1, 2, 5) distinctly infuscate on about apical half anteriorly, at bend of M1+2 and at crossvein dm-cu. Bend of M1+2 oblique, with two short hanging veins. Insertion points of dorsocentral and other mesonotal bristles (Fig. 3), and of ad and pd bristles on tibiae II and III (Figs 2, 5) distinctly infuscate. Antenna (Fig. 3) with first flagellomere subcircular, about as wide as long. Male (Fig. 4): tibia I with one pale curved ventral preapical bristle, and tarsus I with a dense white ventral pilosity from apex of tarsomere taI1 onwards.

Redescription. Male. Body size: 4.6 mm, wing size: 4.9 mm. Head. Face silvery white, nearly parallel-sided, 1.2x as long as postpedicel (MSSC). Palpus very small, half moon-shaped, pale yellow, with black pubescence and one black apical bristle. About upper 1/3 of postoculars black, lowermost 2/3 white. Antenna (Fig. 3) with scape and pedicel yellow, scape slightly infuscate dorsally; postpedicel dark brown, subcircular, as long as wide; stylus dorsal, inserted at about apical 1/3 of postpedicel, 1.7x as long as first three antennal segments combined, with very short pubescence. Thorax. Mesonotum mainly bronze, dusted, with 2 rather wide green longitudinal bands along dorsocentral bristles, with distinct bronze insertion points of bristles; scutellum with marginal fringe of minute white setae, and a few minute setae on disk near anterior margin. Over 10 acrostichal bristles, biserial, reaching beyond 4th dorsocentral bristles. Bristle arrangement otherwise typical of Dolichopus. Wing (Figs 1, 2, 5) mainly hyaline, distinctly infuscate on about apical half anteriorly, at bend of M1+2 and at crossvein dm-cu. Vein M1+2 with oblique bend, bearing two short hanging veins (as in species of the Dolichopus ziczac Wiedemann, 1824 species group) with anterior one distinctly shorter than posterior one, slightly converging with vein R4+5 at wing apex. Proximal section of M1+2 only slightly longer than apical section. Proximal section of CuA1 2.7x as long as apical section. CuA x ratio 1.6. No anal lobe. Halter yellow, calypteral fringe with short yellowish white posterobasal setae, and long black apical setae. Legs mainly yellow to brownish yellow, except for coxae II and III, with insertion points of ad and pd bristles on tibiae II and III distinctly infuscate (Figs 2, 5). Coxa I mainly yellow, with about basal 1/3 infuscate, and frontal face dusted greyish; with less than basal ½ with white pubescence, and more than apical ½ with black bristles. Coxae II and III dark brown, sometimes with yellow apex; coxa III with one black bristle at basal 3/5, and small white setae. Trochanters I-III yellow. All bristles of legs black, unless otherwise mentioned. Femur I entirely dark yellow, with large pv zone with sparse white pubescence (MSSC). Femur II dark yellow, brownish ventrally along basal 2/3, with one large preapical ad bristle. Femur III dark yellow with dark brown knee, and extreme apex whitish yellow; with ventral ¼ (width) brownish along basal 2/3; with one ad preapical bristle and without erect basodorsal bristles. Tibia I yellow, with black apex on anterior face, with 4 strong ds and 2 vt bristles; with ad serration of short bristles mainly on apical ½; with one black ap and one curved pale (brownish at basis, white at apex) preapical av bristle (Fig. 4) (MSSC). Tibia II whitish yellow, with 4 ad, 2 pd, and 5 ap bristles, and 1 av bristle at apical 2/5. Tibia III whitish yellow, with apical 1/10 brown; with 5 ad and 4 pd bristles, one ds preapical and 2 ap bristles; with 3 small vt bristles. Tarsus I (Fig. 4) yellow, darker from apex of taI1 onwards; with dense vt white pilosity on about apical ¼ of taI1, and on taI2-5 (MSSC). Tarsus II yellow with taII1-2 darker on apex, taII3 dark on apical 1/2, and taII4-5 entirely dark. Tarsus III brownish yellow, with taIII1-4 darkened on apex, and taIII5 entirely dark; taIII1 with 1 dorsal bristle. Size (length) ratio of femur/tibia/tarsomeres1-5, in leg I: 5.3/9.5/4.3/2.2/1.7/1.2/1, in leg II: 6.6/7.6/4.3/2.7/1.6/1/1, and in leg III: 6.7/9.9/3.3/3.3/2.1/1.4/1. Abdomen with tergites brilliantly green, mainly dusted laterally, coppery near anterior and posterior margins; sternites black to coppery, tergite I with small white setae laterally. Hypopygium rather small, reaching posterior 1/3 of tergite III; without conspicuous epandrial lobes or surstylar processes, cercus small, white with narrow dark brown margin, and simple marginal bristles (Fig. 2; see also Meuffels, 1981, fig. 3). Female. Body size: 4.6 mm, wing size: 4.4– 4.8 mm. As male, except for: face 1.7x as wide as postpedicel, latter slightly wider than long. Femur I with small elongated vt bare area near base. Tibia I without curved preapical av bristle. Tarsus I pale yellow, dark brown from apical ½ of tarsomere I3 onwards, without ventral pilosity. Tarsi II and III pale yellow, with ta1-4 slightly infuscate at apex, and ta5 dark brown. Size (length) ratio of femur/tibia/tarsomeres1-5, in leg I: 9.0/9.3/4.8/2.0/1.5/1/1.3, in leg II: 7.8/8.8/4.5/1.8/1.7/1/1, in leg III: 6.7/9.6/2.9/3.0/1.9/1/1.

Type material examined. Dolichopus nimbatus: HOLOTYPE ♀ [white], “ MUSEUM PARIS ” / “ CAMP DE ZEITENLIK [Greece]” / “prês SALONIQUE” / “ ARMEE D’ORIENT” / “D’RIVET 1917”; [white] “OCTOBRE”; [white] “ Type ” / “ Dolichopus ” / “ nimbatus Parent ” / “det O. Parent (MNHN)”.

Dolichopus balius: ♂ [white], “ GARD [France]”/ “ La Capelle ” / “ 25.7.79 ”; [white] “ Dolichopus ♂ ” / “ balius Meuffels ” / “det H.G.J. Meuffels ”; [red] “ paratype (FSAG)”. ♀ [white], “GARD” / “La Capelle” / “ 20.iv.1980 ”; [white] “ Dolichopus ♀” / “ balius Meuffels ” / “det H.G.J. Meuffels”; [red] “paratype (FSAG)”.

Additional material examined. BELGIUM: 1 ♂, Province Oost-Vlaanderen, Honegem Nature Reserve (between Erpe-Mere and Lede), sampling site HELI (WID/2004/03), ES7045, open marshland, 2–8.x.2004, Malaise trap, leg. W. D'Haeseleer (Pollet 2012)— first record for Belgium. FRANCE: 1 ♀, Département du Nord (Région Nord-Pas-de-Calais), Raismes-Vicoigne, Parc Naturel Régional Scarpe-Escaut, Mare de Prussien, 50°24′29.18″N, 3°26′58.44″E, marshland, vi–viii.1997, YPT, leg. C. Sibold. GREECE: 1 ♂, Province Serres, Kerkini, Lake Kerkini, Café Elodia (sampling site), 41°12′46.8″N, 23°05′42.9″E, 40 m, 10–16.iii.2008, Malaise trap, leg. G. Ramel (all W; in MAPC).

Other records (specimens not examined). BULGARIA: 1 ♀, no additional information (Knézy 1929). GERMANY: Schleswig-Holstein (Tischler 1948; the specimen was identified by W. Emeis, and is probably currently present in W. Emeis Collection in Flensburg, Germany, but could not be examined). HUNGARY: 1 ♂, Kalocsa (Pester Komitat); 1 ♀, Gyón (Knézy 1929). TURKEY: 1 ♂, Antalya Province, Manavgat, Lake Titreyengöl, 36.757′N 31.455′E, 25.iii.2007, sweep net, leg. N. Vikhrev (ZMUM) (see http://www.diptera.info/ photogallery.php?photo_id=1374).

Remarks. From a morphological perspective, D. nimbatus does not seem related to any of its European congeners, which confirms the conclusions of the previous authors (Parent 1927; Knézy 1929; Meuffels 1981). Species like D. nitidus Fallén, D. griseipennis Stannius and D. diadema Haliday also feature an oblique M1+2 bend, however, with only the posterior hanging vein. Species of the Dolichopus ziczac species group have both hanging veins, but differ from D. nimbatus in many other ways; e.g., different hypopygial structure (Grichanov 1998; Zhang et al. 2009; Selivanova et al. 2010). The short subcircular 1st flagellomere is not shared with any other European Dolichopus species, which also holds true for the ventral pilosity of tarsus I. A strongly supported clade of Dolichopus species does show a short erect ventral pubescence on the fore tarsus (Bernasconi et al. 2006), but this is most likely not homologous with the pilosity in D. nimbatus. Moreover, all species of this clade share a dorsal bristle on metatarus II, which is absent in D. nimbatus.

Meuffels (1981) mentions another three males of D. balius from the same site collected on 20 April 1980.

Distribution. The website Fauna Europaea (Pollet 2011) currently only displays the presence of Dolichopus nimbatus in mainland Greece. The following countries can be added now: Belgium, France, Germany (?), Hungary, Bulgaria and Turkey. Although these records suggest a primarily southeastern European distribution, I assume that the species occurs all over Europe (excl. Fennoscandia), but that other factors have prevented a more extensive and representative recording (see further).

Ecology. In Belgium, D. nimbatus has been collected in an open swamp within an agricultural area. The Mare de Prussien sampling site in France comprises wetlands bordering a lake with vegetation composed of Juncus effusus, Phragmites australis, Deschampsia cespitosa, Cirsium palustre, and Eupatoria cannabinum. This site was bordered by Salix sp. and Alnus sp. along the edge of a Quercus – Betula pendula forest, and flooded from November to May (Cédrik Sibold, pers. comm.). Also in La Capelle (type locality of D. balius), the habitat is a natural shallow lake that dries up in summer (Meuffels 1981). In Greece (Kerkini), it was collected in an area of rough grassland alongside the marshes of an old river bed (Gordon Ramel, pers. comm.). The Malaise trap that produced the sample was immediately adjacent to reeds and a willow tree, about 2 m from the water surface. In Turkey, the species was swept (possibly several specimens) from grassy vegetation in a marshy site near a lake (Titreyengöl), with pastures extensively grazed by horses, and with brashes (ruderal sites with broken rocks and rubbish), wetland, and temporary pools (in March), surrounded by suburban area and pine forests on sandy dunes (Nikita Vikhrev, pers. comm.). In summary, the habitat of the species might be described as open grassland or marshland mostly bordering large stagnant water bodies, often flooded during winter and spring, and drying out during summer.

It is unclear why this seemingly widespread species has not been collected more often. One explanation might be that it is extremely stenotopic and entirely confined to its habitat which implies that this specific habitat must be investigated to encounter the species. Swamps that are flooded most of the year are not the most appealing collecting sites for dipterists. Another factor that most certainly contributes to its scarcity in collections is its seasonal activity that differs considerably from that of any other Dolichopus species in Western Europe. Not taking climatological effects at different latitudes into account, collection dates vary from March-April over July to October, with most specimens encountered in (very) early spring. As most dolichopodid workers conduct collecting mostly from late spring to late summer (May-August), activity peaks of this species might thus be missed. For that reason, it might be quite rewarding to investigate grassy habitats along lakes in early spring and late autumn.