Episyrphus balteatus (De Geer, 1776):116

Episyrphus can usually be readily recognized by the peculiar double-banded pattern of the terga. It is almost certainly closely related to Meliscaeva, the only other genus consistently with discrete black sclerotized dots along the posterior wing margin. It is by far the most widespread of the strictly Old World genera, but I know of only one species in Europe and two in Africa. It is surprising that a genus with at least one species [balteatus (De Geer)] extremely abundant and widespread (England to Japan and India), and with migratory habits, has not spread to the New World. It is also absent from much of the Pacific, apparently not extending farther east than Bonin Is., Solomon Is., New Hebrides, and New Caledonia (from VOckeroth 1969).

Episyrphus s. str. species have eye bare, antenna short, abdomen suboval, metasternum pilose, wing margin with a series of minute closely spaced black maculae on posterior margin, metacoxa without tuft of pile, and anterior anepisternum pilose at least posterodorsally.

Episyrphus (Episyrphus) balteatus (De Geer, 1776).

de Geer, C. (1776) Memoires pour servir a l'histoire des insectes. P. Hesselberg, Stockholm. Vol. 6, viii + 523 pp., 30 pls.

Some authors (Hippa 1968; van Veen 2004) have treated the species of the genus Meliscaeva as species of Episyrphus.

Episyrphus balteatus is sometimes called the marmalade hoverfly.

Synonyms:

Syrphus nectareus Fabricius, 1787: 341.

Syrphus pleuralis Thomson, 1869: 497.

Syrphus proximus Abreu, 1924: 40.

Musca balteata De Geer, 1776: 116.

Syrphus signatus Abreu, 1924: 41.

Musca alternata Schrank, 1781: 448.

Musca cannabina Scopoli, 1763: 344.

Musca scitule Harris, 1780: 111.

Syrphus andalusiacus Strobl, 1899: 145.

Episyrphus fallaciosus Matsumura, 1917: 18.

Episyrphus hirayamae Matsumura, 1918: 12.

Musca scitulus Harris, 1780: 105.

Musca nectarina Gmelin, 1790: 2876.

Syrphus cretensis Becker, 1921: 52.

Musca palustris Scopoli, 1763: 345.

Musca elegans Villers, 1789: 464.

Syrphus alternatus Rossi, 1790: 297.

New description:

MALE.

Head: Face with facial tubercle, yellow, yellow pilose, broadly white pollinose; gena yellow, whitish pilose; lunule yellow with a black dot dorsad to each antenna; frontal triangle yellow, yellow and black pilose; holoptic, eye bare; vertical triangle black, black pilose; antenna orangish-yellow, basoflagellomere orange, darker dorsally; occiput black, white pollinose, withish-yellow pilose.

Thorax: Scutum bronze with dorsomedial narrow silvery pollinose vitta and two submedial broad silvery pollinose vittae, with broad area silvery pollinose anterior to scutellum, yellow pilose; postpronotum yellow, bare; notopleuron densely yellow pollinose, yellow pilose; scutellum yellow, black pilose posteriorly, yellow pilose anteriorly and laterally, subscutellar fringe complete with yellow pile. Pleuron black, yellow pollinose, yellow pilose; anterior anepisternum pilose; metasternum pilose; calypter yellow; plumula yellow; halter yellow; spiracular fringes yellow. Wing: Wing membrane hyaline; apically microtrichose, cell BM bare, microtrichose only on apical 1/4; cells R and R1 bare basally before RS furcation. Alula broad, microtrichose. Legs: Entirely yellow, coxae brownish.

Abdomen: Parallel-sided, unmargined. Dorsum mainly yellow, black pilose dorsally and laterally except 1st tergum yellow pilose and 2nd tergum yellow pilose except posterior 1/5, 3rd tergum black pilose except anterolateral 1/5. 1st tergum yellow, black anteromedially; 2nd tergum yellow with black fascia on posterior margin and medial black fasciate macula that reaches anterior margin with a black vitta on anterior half; 3rd tergum yellow with black fascia on posterior margin and two medial black, arcuate, fasciate maculae that can be joined medially forming a fascia; 4th tergum yellow with black fascia on posterior half (but not on posterior margin) and two medial black, arcuate, fasciate maculae that can be joined medially forming a fascia; 5th tergum yellow; sterna yellow, sterna 2-4 with medial black rounded macula; male genitalia small.

FEMALE.

Similar to male, with frons densely yellow pollinose laterally.

GenBank accession number for this species are: putative torso protein (tor) mRNA (HM044920), gstd1 gene (AJ843575), zerknullt mRNA (DQ323932; EU999029; EU999030; EU999031), putative hunchback (hb) mRNA (FJ387227; FJ387228; FJ387229), putative orthodenticle (otd) mRNA (FJ387225), putative nanos (nos) mRNA (FJ387226), putative caudal (cad) mRNA (FJ387230), even-skipped mRNA (AY645031), hairy mRNA (AY645032), putative huckebein protein (hkb) mRNA (HM067828), putative bicoid protein (bcd) mRNA (HM044914), putative giant protein (gt) mRNA (HM044915), putative knirps protein (kni) mRNA (HM044916), putative knirps related (knrl) mRNA (HM044917), putative Kruppel protein (Kr) mRNA (HM044918), putative tailless protein (tll) mRNA (HM044919), rRNA 12S gene (AY573076; ), 16S gene (AY573115), 28S gene (EF127416; EU241788), 18S gene (EU241840), protein-coding COI gene (EF127335; EU241740), COII gene (AY573151).

The genus Episyrphus has been always related with Meliscaeva. Rotheray and Gilbert (1989) recovered Episyrphus as sister group of Meliscaeva plus a group of Syrphini genera. A different placement was suggested by Rothery and Gilbert (1999), with Meliscaeva as sister group of Episyrphus plus Betasyrphus.

A very new phylogenetic position was suggested by Mengual et al. (2008a). They recovered Episyrphus as sister group of Meliscaeva, being Asarkina the sister group of both. These three genera were placed as sister group of Allograpta+Sphaerophoria, a similar result obtained by Mengual et al. (2008b).

Flowers visited by adults: visits a wide range of white and yellow flowers, from trees to low-growing plants and including nectarless flowers; also visits pink flowers such as Cirsium and Succisa (see de Buck 1990 for an extended list of plants visited by this species). In October/November the species uses flowers of plants such as Arbutus unedo, Hedera and Viburnum tinus. Aspects of the use of flowers by E. balteatus are discussed by various authors, e.g. Sutherland et al (1999) (from Speight 2010).

Larvae of E. balteatus are generalist about species, and thay have been reported feeding on many different species of Aphididae, and some Adelgidae, Psyllidae, larvae of Lepidoptera, and on Coccidae and Phylloxera quercus ( Phylloxeridae) (Rojo et al. 2003).

Flight period for European specimnes is from February to November, with a number of overlapping generations; overwinters as an adult and may be found hibernating among ivy, or in caves etc. On exceptionally mild, sunny days in mid-winter this species can sometimes be found in flight - presumably specimens that have been hibernating. Sarthou et al (2006) show that the occurrence of E. balteatus adults under these conditions is linked to availability of shelter and potential resting/hibernation sites (in forest), in an agricultural landscape. This species is a pronounced migrant (from Speigth 2010).

E. balteatus is probably one of the most wide-spread species of Syrphidae, ranging from Fennoscandia to the Mediterranean; Canary Isles, Azores and North of Africa; Ireland through Eurasia to the Pacific coast; south through the Oriental region to Sri Lanka; and Australia. This is an extremely migratory species and records from offshore islands of northern Europe, such as the Faroes (Jensen, 2001) are assumed to be due to annual immigration, rather than indicative of the occurrence of resident populations.

Adults usually fly within 2 m. of the ground; active under cloudy conditions as much as in the sun; highly migratory; males hover up to 4 - 5 m., usually over paths in woodland, or similar situations (Speight 2010).

Adults' preferred environment: highly anthropophilic and almost ubiquitous.

The larva of E. balteatus has been described and figured by various authors, notably by Bhatia (1939). It is incorporated into the keys provided by Rotheray (1994), who also figures the larva in colour. The morphology of the chorion of the egg is figured by Kuznetzov (1988). Egg morphology is described by Chandler (1968), oviposition behaviour by Bargen et al (1998) and Scholz and Poehling (2000) and various aspects of egg development are detailed by Branquart and Hemptinne (2000), who establish that a female of this species can lay between 2000 and 4,500 eggs during its adult life. The larva is aphidophagous on a wide range of low-growing plants including various crops (e.g. Beta, Lactuca, Solanum, Trifolium spp., Triticum), shrubs (e.g. Buddleja, Euonymus, Sambucus) and trees; Kula (1982) records that E. balteatus shows a preference for aphid colonies low down among the foliage, when its larvae are found on spruce (Picea). Dusek and Laska (1974) and Bargen et al (1998) escribe elements of larval biology and Bombosch (1957) and Tanke (1976) give accounts of laboratory culture of the species. Branquart (1999) shows that development time (from egg-laying to eclosion of adult) in this species can be as little as 3 weeks.

An extensive literature has grown up around this species, because it may be readily cultured under laboratory conditions. It has to be recognised that, although larvae of this species may occur abundantly in crops their presence does not necessarily lead to abundant adults - pesticides used to control aphids can lead to 100% mortality of E. balteatus larvae. There can also be sublethal effects of pesticides on the insects, for instance reduction of fecundity, in females that have developed in treated crops (see, for instance, Colignon et al, 2003). Barkemeyer (1994) provides an extensive and comprehensive review of the literature concerning this species and its biology. While it has been long recognised that this species can overwinter as an adult, only recently has it been established thsat it can also overwinter as a larva (Sarthou et al, 2006).

Egg (Chandler 1938).

White, usually greying slightly on development; mean length 1029 µ (n = 233, range 880-1120 µ), mean width 387 µ, lightly rounded at both ends, surface patterning of frosted white plates with wavy edges. Chorionic sculpturing: dorsally, particulate central area with fine side branches frequently in contact with those of neighbouring units, axes obscure or absent; ventrally, discrete particulate units, more irregularly margined than those in Meliscaeva auricollis and with fine-pointed, inconspicuous side-branches mid-ventrally as well as lateroventrally. Ecological notes: Found from March to October; not common during spring, but abundant from June to August; very wide host acceptance range; eggs not always laid singly.

Larva (Dixon 1960).

Length 10-11 mm., width 2.5 mm., height 2.5 mm.; adipose tissue white, distinctive superficial pattern of five groups of two consecutive transverse bars of adipose tissue present connecting a sometimes incomplete fine line of adipose tissue on either side of heart line; Malpighian tubules appearing orange through integument; subcylindrical, tapering anteriorly, cuspidate posteriorly; fleahy projections and prominences absent; integumental vestiture absent; body papillose; segmental ornamentation of fine cone-like pegs on slightly enlarged papillae. Posterior respiratory process: three-fourths as long as broad; completely sclerotized, smooth; constricted one-third distance from the base; circular plates large and oval; dorsal spurs reduced to (L small fold on inner borders of circular plates; interspiracular ornamentation of four pairs of inconspicuous nodules; spiracles equidistant, raised on carinae slightly above level of spiracular plates; III parallel to median groove, angle between I and III 135°; fringe of hairs present on inner border of spiracles. Source of material: Collected from trees, shrubs and herbs at Silwood Park from, June to September.