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.
Following the database Systema Dipterorum (Pape and Thompson 2010), Chrysotoxum festivum is a junior sysnoym of C. arcuatum. Speight (2010) states that: "The confused history of the use of the name festivum (L.) has made European literature on this species almost unusable". Speight (2010) also says that arcuatum Linnaeus is ignored and not used by him because the confusion with this name following the ICZN, but this comment is under Chrysotoxum fasciatum (Muller, 1764).
Synonym:
Musca festiva Geoffroy, 1785: 479.
Chrysotoxum arcuatum (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, golden pollinose posteriorly; vertical triangle black, black pilose; antenna dark, elongate, scape, pedicel and basoflagellomere elongate, subequal; 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 yellow with a medial black macula, black on anterior margin, yellow and black pilose, subscutellar fringe complete with yellow pile. Pleuron mostly black, except posterior anepisternum black on posterior half, katepisternum with dorsal yellow macula, proepimeron and katatergum with yellow macula, golden yellow pilose; metasternum bare; calypter yellow; plumula yellow; halter yellow; spiracular fringes yellow. Wing: Wing membrane yellowish, yellow on anterior half; entirely microtrichose. Alula broad, microtrichose. Legs: Entirely yellow except coxae and trochanters dark brown to black, femora orangish.
Abdomen: oval, strongly convex dorsally, terga 2-5 strongly margined. 1st tergum black, yellow pilose; 2nd tergum black with two anterior, narrow, arcuate yellow maculae, which do not reach lateral margins; 3rd and 4th terga black with two anterior, strongly arcuate, yellow maculae not reaching lateral margins; 5th tergum black with with two anterior, strongly arcuate, yellow maculae. Sometimes, terga 3-5 with very narrow fascia on posterior margin, broader on tergum 5. Sterna brown to black, except sterna 3and 4 with two yellow fasciate maculae on anterior margin.
GenBank accession number for this species are: 5.8S ribosomal RNA gene, partial sequence and internal transcribed spacer 2, complete sequence (AY903989; AY903988; AY903987), and partial cytochrome oxidase subunit I (COI) gene, complete tRNA-Leu gene, and partial cytochrome oxidase subunit II (COII) gene (AY903968).
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; Calluna, Chaerophyllum, Cirsium arvense, Euphorbia, Galium, Hieracium, Hypochoeris, Narthecium, Origanum, Potentilla erecta, Ranunculus, Rosa rugosa, Rubus idaeus, Sambucus nigra, Senecio, Solidago canadensis, S.virgaurea.
Larvae prey for C. arcuatum 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 May to September, with peaks in June and August.
Wide-spread species raging from Fennoscandia south to Iberia and the Mediterranean, including North of Africa; from Ireland eastwards through much of Europe into Turkey and European parts of Russia; through Siberia to the Pacific coast; Japan; and northern India (Speight 2010 as Chrysotoxum festivum).
Adults inhabit clearings, tracksides etc.; males hover at 2- 4 m.; flies fast through scrub and bushes.
Adults' preferred environment: forest/open ground, open areas in scrub woodland and deciduous forest; unimproved grassland with scrub.
Puparium of C. arcuatum was described and figured by Speight (1976), who found the mature larva with the ant Lasius niger, beneath a stone in Corylus/Prunus scrub on old pasture.
unless otherwise stated