Vockeroth (1969) gave a genus diagnosis for Syrphus.
Small to medium sized, robust species with mesonotum yellowish- or greyish-pollinose laterally and tergites with transverse yellow fasciae or pairs of maculae.
Eye usually bare, rarely sparsely or densely pilose. Front and face of male rarely slightly swollen, in this case the face broad and with indistinct tubercle. Face usually entirely yellow, rarely with a very narrow brown median vitta. Basoflagellomere usually short oval and broadly rounded apically, rarely slightly elongate and subacute. Scutum shining or subshining, aeneous to black, sometimes with faint, dark, narrow median and submedian vittae; sides of scutum and all of pleura usually slightly but distinctly yellowish- or greenish-grey pollinose. Dorsal and venrtal katepisternal pile patches joined posteriorly by narrow band of hairs. Metasternum bare. Lower lobe of squama almost always with many long erect pale pile on at least posteromedian part of upper surface, these hairs few in number or absent only in one species from Patagonia. Metacoxa with tuft of pile at posteromedian apical angle. Abdomen oval, narrow to moderately broad, slightly convex dorsally, weakly margined from about middle of tergum 2 to apex of tergum 5 or 6. Tergum 2 with a pair of yellow maculae, terga 3 and 4 with sharply defined, often somewhat undulate, narrow or broad, entire or divided, bright yellow fasciae which mayor may not extend to lateral margins. Sterna yellow.
MALE TERMINALIA. Surstylus short, broad, curved slightly ventrad, bluntly rounded apically; inner surface with weak marginal flange dorsally and posteriorly except at apex. Sternite 9 with moderate emargination posteroventrally, with long, rather slender, slightly tapering lingula which is either subcylindrical or grooved on dorsal surface and is curved very slightly to strongly ventrad near its apex. Superior lobe long, broad, directed posterodorsad, strongly compressed, with many minute setae laterally; anteroventral angle with a short recurved hook, ventrolaterally and posterolaterally with a very low compressed submarginal flange which ends posterodorsally in a short projecting tooth. Aedeagal base subtriangular in profile, deeper and slightly compressed dorsally, projecting ventrad as a flat, depressed, apically truncate or apically rounded plate which almost always bears a small to moderately large, anteriorly directed, sub lateral or lateral tooth on each side near apex. Distal portion of aedeagus subtriangular or somewhat depressed in section, flattened posterodorsally and subcarinate anteroventrally, the apex only slightly weaker and slightly to strongly flared laterally and ventrally, with many minute pale spicules anteriorly.
Head: Face with distinct tubercle, gradually sloping dorsally, more abrupt ventrally, yellow, yellow pilose with black pile dorsolaterally, yellow pollinose laterally; gena yellow, yellow pilose; lunule yellow medially; frontal triangle yellow with a medial dark brown macula not reaching posterior margin, black pilose, yellow pollinose posteriorly; holoptic, eye bare; vertical triangle black, black pilose; antenna brown, basoflagellomere orange basally; occiput black, yellowish-grey pollinose, whitish-yellow pilose.
Thorax: Scutum black, yellow-bronze pollinose except anteriorly, with lateral yellow pollinose vitta, yellow pilose; postpronotum bare; scutellum yellow, black pilose, yellow pilose basally, subscutellar fringe complete with yellow pile. Pleuron black, densely yellow pollinose, yellow pilose; anterior anepisternum bare; metasternum bare; calypter yellow, ventral lobe with many long erect pile dorsally; plumula yellow; halter yellow; spiracular fringes yellow. Wing: Wing membrane hyaline, entirely microtrichose. Alula broad, microtrichose. Legs: Entirely yellow with pro- and mesofemora black on basal 1/4; metafemur brown to black on basal half; metatibia dark yellow, slightly arcuate; tarsi brown.
Abdomen: Slightly oval, terga 2, 3 and 4 vaguely margined. Dorsum mainly black, black pilose dorsally and laterally except 1st tergum yellow pilose and 2nd tergum yellow pilose on basal 1/2; tergum 1 black; tergum 2 black with 2 mesolateral round yellow maculae, extended forward laterally to anterolateral tergum margin (like “golf club” shaped spots); terga 3 and 4 black with anteromedial broad yellow fascia, with posterior margin sinuose, tergum 4 with yellow fascia on posterior margin; 5th tergum yellow with medial black macula; sterna mainly yellow, dark yellow posteriorly on terga 3 and 4, yellow pilose.
Whether the enigmatic, European, female specimens referable to S. rectus Osten Sacken represent a distinct species or a variant of S. vitripennis is as yet unclear, but whatever they represent, using existing keys except those of Speight (1988a) and Goeldlin (1996) such specimens would be misdetermined as S. ribesii, since their legs are yellow as in female S. ribesii. They may easily be distinguished by the large areas bare of microtrichia on their wings, which are entirely covered in microtrichia in S. ribesii. Boyes et al (1971) show that over much of Europe there are two chromosome races of S. ribesii, as currently defined, one with 2n = 8, the other with 2n = 10. It is not known if these races have any taxonomic significance (Speight 2010).
Dusek and Laska (1967) placed Syrphus in their tribe Syrphini, with Leucozona and Ischyrosyrphus as sister groups. Vockeroth (1969) considered it also Syrphini, and following his disposition within his work, Syrphus was somewhat related with Epistrophe and Epistrophella.
Rotheray and Gilbert (1989) recovered Syrphus as sister group of many genera, with Meliscaeva as sister group of these genera plus Syrphus. Rotheray and Gilbert (1999) recovered Syrphus in a different position: Syrphus was resolved in a polytomy with Fagisyrphus, Parasyrphus and Melangyna as siter group of many genera, being Meliscaeva the sister group of these genera plus Syrphus.
Ståhls et al. (2003) recovered Syrphus as related with Chrysotoxum, but their taxon sampling was not done thinking on Syrphinae. The same result was obtained by Hippa and Ståhls (2005). Mengual et al. (2008) resolved Syrphus as sister group of Parasyrphus, and both as sister group of Eupeodes and Scaeva clade.
Adults visits a wide range of yellow, white, pink and blue flowers, including composites and umbellifers and the flowers of many trees and shrubs (see extended list in de Buck, 1990).
Larvae of S. ribesii have been reported feeding on Adelgidae, Aphididae, larvae and eggs of Melasoma aenea (Coleoptera) and larvae of Lepidoptera (see a full list of species in Rojo et al. 2003).
Flight period for European specimens is from April to mid November (plus March in southern Europe), with peaks in May and August (Speight 2010).
S. ribesii ranges from Iceland and Fennoscandia south to Iberia and the Mediterranean; Canary Isles; from Ireland eastwards through most of Europe into Turkey, European parts of Russia and Afghanistan; from the Urals to the Pacific coast (Kuril Isles); Japan. In North America, from Alaska to New Brunswick, south to Mexico (Speight 2010; Thompson 2010).
Adults inhabitat gardens, tracksides, clearings, hedgerows etc.; flies up to 5 m from ground; males hover at 2-5 m (Speight 2010).
Preferred environment by adults: anthropophilic, occurring in farmland, orchards, horticultural land, suburban gardens and parks, conifer plantations; also in most types of deciduous and coniferous forest (Speight 2010).
Larva of S. ribesii was described and figured by Dusek and Laska (1964); it is aphid feeding on various herbaceous plants (e.g. Carduus, Eryngium, Sonchus, umbellifers), including some crops (Beta, Triticum, Vicia, Zea), bushes (e.g. Rubus spp.) and shrubs. The larva of this species apparently occurs in a number of distinct colour forms, as illustrated in colour by Rotheray (1993) and Bartsch et al (2009a). Egg: Chandler (1968). The morphology of the chorion of the egg is figured by Kuznetzov (1988). Laboratory culture detailed by Bombosch (1957).
Egg (from Chandler 1968).
White, greying slightly on development; mean length 957 µ (n = 230, range 820-1110 µ), mean width 427 µ; strongly tapering towards one end; marked surface projections dorsally and laterally. Chorionic sculpturing: dorsally, projections mushroom-shaped, neck wider than long, appearance of units dendritic, ramification with extensive contact between branches of neighbouring units; ventrally, sculpturing of large dots and rods not aggregated into discrete groups. Ecological notes: Common; eggs found from May to October; wide host acceptance range; eggs laid singly.
Third instar larva (from Dixon 1960).
Length 9.0-11.5 mm., width 2.5 mm., height 2 mm. ; from a fine cream line on either side of heart line five segmentally arranged postero-laterally directed oval groups of white to bright yellow adipose tissue; adipose tissue occasionally entirely pink in some specimens, gut contents appearing black beneath adipose tissue; subcylindrical, tapering anteriorly, cuspidate posteriorly; felashy projections and prominences absent ; integumental vestiture restricted to a few fine dark hairs round mouth; body papillose; segmental ornamentation typical. Posterior respiratory process: half as long as broad; smooth; sclerotized; constricted one third length from base; circular plates round; dorsal spurs prominent and broadly triangular in side view; interspiracular ornamentation consisting of four pairs of well-developed nodules; spiracles straight, equidistant, mounted on dark carinae; I and 111 slightly less than 180º apart; a fringe of hairs present on inner border of spiracles.
Source of material: collected from trees, shrubs and herbs at Silwood Park from June to October.
This species is highly migratory (Speight 2010).