Paragus (Paragus) bicolor (Fabricius)
Paragus (Paragus) bicolor (Fabricius, 1794).
Fabricius, J.C. (1794) Entomologia systematica emendata et aucta. Vol. 4,  + 472 +  pp. C. G. Proft, Hafniae [=Copenhagen].
Paragini, with the single genus Paragus, is a compact and distinctive group occurring in all continents other than South America and Antarctica. Paragus species are small, slender to moderately robust, with thorax black or with apex of scutellum pale, and abdomen usually extensively red-orange to entirely black. Paragus has postpronotum bare, antenna short, anterior anepisternum bare, abdomen parallel-side, face yellow in background colour, metaepisternum bare, scutum black laterally, at most with a poorly defined yellow polinose vitta, and metasternum bare.
The subgenus Paragus sensu Vujic et al. (2008) has eyes with vertical medial vitta of shorter pile; face with distinct facial tubercle; scutum with or without pollinose submedial vitta; scutellum without conspicuous teeth on posterior margin, rhomboidal; spurious vein ending before the meeting point of vein M1 with vein DM; abdomen short and elliptical; terga 1–2 completely fused; terga 3–5 fused laterally; male genitalia: postgonite curved posteriorly; ejaculatory apodeme with four apical ridges; minis large, lateral arms of minis short; epandrium in narrower part twice length of cercus; lateral lobe of aedeagus fused with aedeagal apodeme; aedeagus in lateral view strongly asymmetric, ‘keel-like’, with well-developedbasal part.
Existing keys do not differentiate P. bicolor from the full range of known, related, European species. At present, identification can only be reliably carried out using features of the male terminalia. The females cannot be identified with certainty, due to the potential for confusion with females of related species, for some of which females are yet to be described.
Head: Face with facial tubercle, light yellow, black on epistoma and gena, whitish-yellow pilose; frontal triangle light yellow, yellow pilose; vertical triangle black, grey pollinose anteriorly, black pilose; scape and pedicel black; basoflagellomere elongate, longer than scape and pedicel together, brown, orange ventrally; arista brown, submedial; dichoptic, eyes separated by facet width, eye pilose, pile arranged in 3 more or less vertical vittae of contrasting colour; occiput black, silver pollinose, withish-yellow pilose.
Thorax: Scutum subshiny black, punctuate, with two dorsomedial broad white pollinose vittae, yellow pilose; postpronotum bare; scutellum punctuate, black basally and yellow on apical 3/5, yellow pilose, subscutellar fringe complete with yellow pile. Pleuron black, whitish pilose with pile tuft of white long pile on dorsal katepisternum and posterior anepisternum; metasternum bare; calypter yellow; plumula yellow; halter yellow; spiracular fringes dark yellow. Wing: Wing membrane hyaline; apically microtrichose, with basal half of cells C, R1, R and BM bare. Alula broad, extensively microtrichose, bare basally. Legs: Entirely brownish-orange except fmora-tibiae joints yellow.
Abdomen: Parallel-sided, convex, punctate; terga 1–2 completely fused; terga 3–5 fused laterally. Dorsum mainly orange; tergum 1 (or its equivalent) black; tergum 2 (or its equivalent) orange; terga 3-6 orange with medial diffuse black areas; terga 3-4 with two submedial arcuate white pollinose fasciate vittae; male genitalia enlarged; surstylus strongly narrowed to slender apex; paramere slender, slightly or strongly curved, directed upward; lateral lobe of aedeagus large, exposed in lateral view.
Ecology and Distribution
Widespread species known from North America (from British Columbia and Yukon to Quebec, south to California and Virginia), Europe (from southern Sweden and Denmark [extinct in Belgium] south to the Mediterranean, from France eastwards through central and southern Europe), North of Africa to Mongolia, Iran and Afghanistan (Speigh 2010).
Adults' preferred environment: open ground; dry, unimproved, sparsely-vegetated grassland and open areas in Quercus ilex forest and maquis (Speight 2010).
Flowers visited by adults: Euphorbia, Herniaria glabra, Potentilla, Sedum, Scleranthus, Solidago (Speight 2010).
Larvae of P. bicolor have been reported feeding on Aphis craccivora, Aphis fabae and Dysaphis sp. (Rojo et al. 2003).
Flight period for European specimens: from May to July; from July to August at higher altitudes (Speight 2010).
Adults fly low among ground vegetation, settling on either bare ground or low plants; as easily detected by sweeping, or Malaise traps, as by direct observation (Speight 2010).
Larva (from Dixon 1960).
Length 7-8 mm., width about 3.25 mm., height about 2.5 mm.; dun or translucent yellow without pattern except for the heart, or light yellowish-brown, semi-transparent, with a dorsal brick-red band about one-third width of the larva and a black median heart line, a black band on either side and a more lateral wide yellowish-white band; elongate oval from above, doraoventrally flattened, gradually tapering, obtuse anteriorly, truncately rounded posteriorly; segments 5-11 with seven pairs of rounded elevations functioning as prolegs; segmental ommentation of pointed spines on processes equally as long; dorsal spines on segments 3 and 6-11 one-sixth as long as other spines. Posterior respiratory process: broader than long (Heiss), slightly longer than broad (Metcalf); basal region roughly papillose, nearly black, separated from the smooth strongly sclerotised distal region by a constriction about halfway along the length; dorsal spurs broad, long, hollowed at the base; interspiracular ornamentation inconspicuous; spiracles on well-developed carinae.
Evolution and Systematics
Nomenclature and Synonymy
Paragus ater Meigen, 1822: 182.
Syrphus bicolor Fabricius, 1794: 297.
Musca cruentatus Geoffroy, 1785: 462.
Paragus ruficauda Zetterstedt, 1843: 852.
Paragus arcuatus Meigen, 1822: 179.
Paragus taeniatus Meigen, 1822: 179.
Paragus tacchettii Rondani, 1865: 140.
Paragus testaceus Meigen, 1822: 180.
Paragus is the only genus of the tribe Paragini and its phylogenetic position is uncertain. Dusek and
Laska (1967) did not comment on the sister group of Paragus but mentioned that the genera Didea and Paragus share some characters of the adult morphology and male genitalia and they placed Paragini as one of the first branches of Syrphinae, commonly called basal clades. Shatalkin (1975) said that Paragini was a tribe aberrant in relation to all other tribes of the subfamily based on characters of the male genitalia. Rotheray and Gilbert (1989) using larval characters, resolved the genus as sister group of the tribe Pipizini. In 1999, Rotheray and Gilbert reported Paragus as sister group of the clade Eupeodes + Scaeva + Ischiodon.
Ståhls et al. (2003) using morphological and molecular characters resolved Paragus as sister group of the genera Chrysotoxum and Syrphus. Hippa and Ståhls (2005), based only on adult morphological cahracters, found a similar conclusion: Paragus as sister group of Chrysotoxum, Syrphus, Toxomerus and Sphaerophoria. Mengual et al. (2008) using only molecules, resolved Paragini as sister group of Allobaccha, a position never suggested before
Although there are recent studies about the intrageneric classification of Paragus (Kassebeer, 1999a,b, 2001; Rojo et al., 2006; Vujic et al., 2008), the placement of this tribe in the subfamily Syrphinae is unresolved as previous results disagree. Currently there are four subgenera based on the study by Vujic et al. (2008): Paragus s. str., Serratoparagus, Afroparagus and Pandasyopthalmus (the latest with two species groups, tibialis and jozanus groups).