Chrysotoxum bicinctum (Linnaeus, 1758):592

Chrysotoxum species have antennae elongate, sometimes longer than head; with basoflagellomere at least three times as long as broad; scape and pedicel often longer than broad; abdomen strongly convex dorsally, strongly margined, usually posterolateral angles of terga projecting.

Chrysotoxum bicinctum (Linnaeus, 1758).

Linnaeus, C. (1758) Systema naturae... Ed. 10, Vol. 1. 824 pp. L. Salvii, Holmiae [= Stockholm].

New description:

MALE.

Head: Face straight with facial tubercle, yellow with medial broad black vitta, brown ventrally until genal suture, yellow pilose; gena yellow, yellow pilose; frontal triangle black, black and yellow pilose; vertical triangle black, black pilose; antenna dark, elongate, scape and pedicel elongate, subequal; basoflagellomere longer; occiput black, silver pollinose, withish pilose ventrally, yellow pilose dorsally.

Thorax: Scutum subshiny black with two dorsomedial white pollinose vittae, yellow pilose with few black pile; postpronotum black, yellow posteriorly, bare; notopleuron mostly yellow, black laterally; scutellum black, yellow on posterior margin, yellow pilose, subscutellar fringe complete with yellow pile. Pleuron mostly black, except posterior anepisternum black on posterior third, sometimes katepisternum with a small dorsal yellow macula, golden yellow pilose; metasternum bare; calypter brownish; plumula brownish-white; halter yellow; spiracular fringes brownish. Wing: Wing membrane mostly hyaline, yellow on costal cell, cell R anterior to vein rm and very basally, with a brown macula on anterior margin from stigma, R1 and R4+5; entirely microtrichose. Alula broad, microtrichose. Legs: Entirely yellow except coxae and trochanters dark brown to black, pro- and mesofemora black on basal third, metafemur black on basal 3/4, metabasitarsomere brown basally.

Abdomen: oval, strongly convex dorsally, terga 2-5 strongly margined. 1st tergum black, yellow pilose; 2nd tergum black with 2 medial, broad (half of tergum length), arcuate yellow maculae, which reach lateral margin shortly posteriorly, and sometimes join medially; 3rd tergum black, yellow on posterior third of the lateral margins; 4th tergum black with strongly arcuate yellow fascia not reaching lateral margins; 5th tergum black with two medial, arcuate, narrow yellow fasciate maculae. Sometimes, terga 3-5 with very narrow fascia on posterior margin. Sterna brown to black, except sternum 2 yellow medially and sternum 3 with anterior yellow fascia.

Synonyms:

Musca bicinctatum Turton, 1801: 639.

Musca bicincta Linnaeus, 1758: 592.

Musca callosus Harris, 1776: 61.

Chrysotoxum tricinctum Rondani, 1845: 201.

Syrphus bicinctus Fabricius, 1775: 767.

GenBank accession number for this species are: cytochrome oxidase subunit I (COI) gene (EF127370), 5.8S ribosomal RNA gene, partial sequence and internal transcribed spacer 2, complete sequence (AY903979; AY903978; AY903977; AY903976), and partial cytochrome oxidase subunit I (COI) gene, complete tRNA-Leu gene, and partial cytochrome oxidase subunit II (COII) gene (AY903960; AY903959; AY903958).

Vockeroth (1969) and previous authors considered Chrysotoxum as monogeneric tribe, Chrysotoxini, or as a different subfamily, Chrysotoxinae (Sack 1932; Hull 1949; Coe 1953). Later Vockeroth placed it into Syrphini (Vockeroth, 1992).

Rotheray and gilbert (1989) recovered Chrysotoxum as sister group of six Syrphini genera: Dasysyrphus, Didea, Megasyrphus, Eupeodes, Scaeva, Eriozona. A similar position was reported by Rotheray and Gilbert in 1999, but this time Chrysotoxum was placed as sister group of a clade with more Syrphini genera. Ståhls et al. (2003) recovered Chrysotoxum as sister group of Paragus and Syrphus using only larval characters, as sister group of Syrphus using the adult morphology dataset and six different parameters dor the DNA dataset. In the combined analysis, Chrysotoxum was placed in a polytomy.

Hippa and Ståhls (2005) also recovered Chrysotoxum as sister group of Syrphus using only adult morphological characters. But Mengual et al. (2008), using three molecular markers, resolved Chrysotoxum as sister group of Epistrophe.

Flowers visited by adults: white umbellifers; Achillea ptarmica, Alisma plantago-aquatica, Carduus, Crataegus, Hypochoeris, Potentilla erecta, Ranunculus, Rubus.

Larvae prey for C. bicinctum are unknown, but the only reported prey for other species of Chrysotoxum are aphids (Aphididae) (Rojo et al. 2003).

The flight period for European specimens is from the end of May to September (Speight 2010).

Chrysotoxum bicinctum ranges from Fennoscandia south to Iberia and the Mediterranean, including North of Africa; through central and southern Europe (Italy, the former Yugoslavia, Bulgaria) into Turkey and European parts of Russia; and in Asiatic parts of Russia as far as central Siberia (Speight 2010).

Adults inhabit among streamside and fen vegetation; they fly fast and low; males hover at 2 - 3 m. along streams; they settle on low-growing vegetation and bushes.

Adults' preferred environment: forest/open ground; beside streams (including seasonal streams) in open areas in coniferous and deciduous forest, up to the lower levels of Abies/Picea forest; also in fen meadow/unimproved, lowland humid grassland including Molinia grassland and along streams and rivers in lowland, improved grassland (speight 2010).

Larva of C. bicinctum is undescribed, but has been reared on a diet of aphids in the laboratory (Rotheray and Gilbert, 1989).