Xanthogramma species have eye bare or pilose; postpronotum bare; basoflagellomere oval; vein R4+5 straight; anepisternum yellow posteriorly; male trochanter simple; wing extensively microtrichose, bare basally, usually dark anteriorly; scutum and katepisternum with sharply defined bright yellow maculae, not pollinose; scutellum always broadly black basally; abdomen margined; metaepisternum bare; and anterior anepisternum bare.
Little is known about the larval biology of this species. Larvae were recorded from Lasius ant colonies (Hoelldobler, 1929; Dixon, 1960) where they may feed on ant-associated aphids (Chandler, 1968). The larval biology has been documented by Pontin (1960). The larvae are predators of the "herds" of root aphids tended by ants of the genus Lasius (Speight 2010).
Synonyms:
Xanthogramma bilobatum Szilady, 1940: 64.
Xanthogramma nobilitatum Frey, 1946: 161.
Xanthogramma nigripes Szilady, 1940: 64.
Xanthogramma flavifrons Szilady, 1940: 64.
Xanthogramma flavipleura Coe, 1957 : 62.
Syrphus ornatus Meigen, 1822 : 298.
Doros decoratus Zetterstedt, 1843: 694.
Musca pedissequus Harris, 1776: 61.
Syrphus dives Rondani, 1857: 136.
Scaeva flavicincta Gravenhorst, 1807: 375.
Syrphus pulcher Meigen, 1835: 69.
Xanthogramma pedissequum (Harris, 1776).
Harris, M. (1776-1780) An exposition of English insects ... Decad I, pp. 1-40, 2 pls. + pls. 1-10 [1776.??.??]; Decad II, pp. 41-72, pls. 11-20 [1778.??.??]; Decads III, IV, pp. 73-99, 100-138, pls. 21-30, 31-40 [after 1779.12.24]; Decad V, pp. 139-166, pls. 41-50 + 1 pl. [1780.??.??]. Robson Co., London.
New description:
MALE.
Head: Face with distinct tubercle, more protruded forward than antennal bases, yellow, yellow pilose with some black hairs on the tubercle and laterodorsally; gena and lateroventral part of the face brown to black; frontal triangle yellow with a brownish macula dorsad to antennal bases, yellow pilose posteriorly and black pilose on anterior half; vertical triangle black, black pilose; antenna orangish, basoflagellomere oval, arista subbasal; occiput black, silver pollinose, whitish-yellow pilose.
Thorax: Scutum and pleuron dark brown to black, with long yellow pile, except scutum with lateral broad yellow vitta from posterior half of postpronotum to postalar callus, and posterior anepisternum yellow on posterior half. Scutellum black, yellow on apical half, without subscutellar fringe, yellow pilose. Anterior anepisternum and metasternum bare; calypter brown; halter brown; spiracular fringes brown. Wing: Wing membrane mostly hyaline, with dark brown macula on vein R1 between furcation of RS and the end of stigma; entirely microtrichose. Alula broad, microtrichose. Legs: Coxae and Trochanters black, pro- and mesoleg yellow; metafemur yellow, brownish on apical 1/2-1/3; metatibia and metatarsi orange; metatibia with brownish ring medially.
Abdomen: Parallel-sided, slightly oval, terga 2 to 5 margined. Dorsum mainly black, black pilose except 1st tergum yellow pilose laterally and 2nd tergum yellow pilose on basal half; 1st tergum black; 2nd tergum black with 2 mesolateral triangular (rounded tip) yellow maculae; 3rd and 4th terga black with anterior narrow arcuate yellow fascia interrupted in the middle; 4th tergum with yellow line on posterior margin; 5th tergum yellow with posterior triangular black macula reaching lateral margins. Sternum 1 black, yellow on posterior half; sternum 2 yellow, black on posterior half; sternum 3 black, yellow on anterior third; sternum 4 black with two yellow macula on anterior margin; sternum 5 black.
GenBank accession number for this species are: protein-coding COI gene (EF127339; EF127295), rRNA 28S gene (EU431470) and 18S gene (EU431557).
Dusek and Laska (1967) designated the tribe Xanthogrammini to include Xanthogramma, Olbiosyrphus (= Xanthogramma) and Doros. Wirth et al. (1965) and Vockeroth (1969) considered this genus as Syrphini and Vockeroth realted it with Citrogramma.
Rotheray and Gilbert (1989) recovered Xanthogramma as the sister group of all the Syrphini genera, except Sphaerophoria. Ten years later, Rotheray and Gilbert (1999) recovered Xanthogramma as sister group of Doros.
Mengual et al. (2008) reported Xanthogramma as sister group of Epistrophella. This position is not consistent with larval evidence.
Flowers visited by adults: umbellifers, yellow composites; Berberis, Caltha, Crataegus, Euphorbia, Lamium, Ligustrum, Potentilla erecta, Pulicaria, Ranunculus, Rosa, Rubus, Sambucus nigra, Stellaria, Ulmus (Speight 2010).
Larvae of this species have been reported feeding on Forda formicaria, Forda sp. and Trama sp. (Aphididae) (Rojo et al. 2003).
Flight period of X. pedissequum is from May to September, with a peak in July (Speight 2010).
The range of X. pedissequum is uncertain due to confusion until recently with both X. dives and X. stackelbergi, but known from Britain and Atlantic seaboard countries south to central France and into central Europe to the Alps (France, Switzerland). It seems that in the Mediterranean zone X. pedissequum is largely replaced by X. dives and X. stackelbergi and the southern European distribution of X. pedissequum is particularly in need of review (Speight 2010). Thompson (2010) considers dives a junior synonym of pedissequum.
Adults fly low among tall grass etc. and settles on foliage of low-growing plants (Speight 2010).
Preferred environment by adults: open ground; unimproved montane grassland and unimproved, lowland humid grassland and open areas along streams in thermophilous Quercus forest and mesophilous Fagus forest; occasionally along grassy road verges or canal banks, or in suburban parks and gardens. This species is almost invariably in well-drained situations, even when close to water (Speight 2010).
Speight (1990) distinguishes the puparium from that of X. citrofasciatum.
Larva of the genus Xanthogramma (from Rotheray and Gilbert 1989).
Diagnosis. Up to 12 mm long; oval in cross-section; off-white colour pattern; vestiture of close-set dome-like papillae; spots on first abdominal segment and pupal horns absent; sensilla pair 11 not on locomotory prominences and anterior to sensilla 10; anal segment with four lobes; prp smooth and rounded and domelike in profile; spiracular slits long, wavy and not mounted on carinae; dorsal spurs absent; interspiracular setae small and set in circular pits.
Recognition features. The off-white colour pattern and wavy spiracles distinguish this genus. Doros larvae are probably similar in many characters and can be separated from Xanthogramma in that the spiracular slits of the former larvae are straight and several interspicular setae are present in each circular pit.
Third instar larvae (from Dixon 1960).
Length 10 mm., width 5 mm., height 4 mm. (1 specimen); uniform cream without markings, smooth, shining; subcylindrical, tapering anteriorly, rounded posteriorly; segmentation indistinct ; transverse wrinkles fine and equally spaced; longitudinal wrinkles and ridges absent; prolegs and claws and fleshy projections and prominences absent; integumental vestiture and papillae absent; segmental ornamentation of minute conical hairs on papillae of equal length. Posterior respiratory process: postero-dorsal; as long as broad; rounded at apex, entirely sclerotized, and constricted halfway along length; spiracular plates not separated by a median groove; circular plates extremely small, slightly larger than pits of interspiracular ornamentation; dorsal spurs absent; interspiracular ornamentation of four pairs of single fine heirs each arising in a small circular pit set well in from the periphery of spiracular plates; three pairs of convoluted spiracles not mounted on carinae, but radiating from circular plates.Source of material: Collected in Oxford in June by Dr. A. J. Pontin from a nest of Lasius niger containing Tram sp.
unless otherwise stated