Xanthandrus comtus (Harris, 1780)

This genus is very close to Melanostoma Schiner, 1860, but it differs from this by possessing larger size of the body and the abdomen elliptic, wide and flat, arista bare, central portion of the epistoma moderately proeminent, face narrow and longer and wider susrtyli. While Melanostoma has arista sometimes pubescent, not proeminent epistoma, terminalia with a susrtilus thin, straight and uniform, reduced metasternum, legs of males narrow, without bristles, and without patterns of hair or modified piles (from Borges and Pamplona 2003).

The most significant morphological characters to separate Xanthandrus specimens are: postpronotum bare, face and scutellum black, metaepisternum with some fine subappresses pile; metacoxa with a pile tuft at posteromedial apical angle; and antennal pits confluent.

Xanthandrus (Xanthandrus) comtus (Harris, 1780).

Harris, M. (1776-1780) An exposition of English insects: with curious observations and remarks, wherein each insect is particularly described; its parts and properties considered; the different sexes distinguished, and the natural history faithfully related : the whole illustrated with copper plates. 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 1776.

Synonyms:

Epistrophe undulata Cepelak, 1940: 33.

Musca comtus Harris, 1780: 47.

Epistrophe reducta Cepelak, 1940: 34.

Syrphus quadriguttulus Matsumura, 1911: 78.

Scaeva saltatrix Gravenhorst, 1807: 374.

Scaeva hyalinata Fallen, 1817: 43.

New description:

MALE.

Head: Face with distinct, round facial tubercle, black with silvery pollinosity except on shiny black tubercle, yellow pilose; gena black, yellow pilose; lunule ornage; frontal triangle black, silvery pollinose except anterior semicircular shiny black area posterior to lunule, black pilose; vertical triangle black, black pilose; antennal pits confluent; antenna brown, basoflagellomere orange ventrally; arista brown, bare; occiput black, silver pollinose, withish-yellow pilose.

Thorax: Scutum and scutellum shiny black with long yellow pile; postpronotum bare, golden pollinose; notopleuron yellow pilose, golden pollinose; subscutellar fringe complete with long yelow pile. Pleuron black, yellow pilose, golden pollinose anterodorsally; metasternum bare; metaepisternum with some fine subappresses pile; calypter yellow; plumula yellow; halter yellow, capitulum darker; spiracular fringes yellow. Wing: Wing membrane hyaline, stigma dark yellow; apically microtrichose, bare basally on 2nd costal cell and cells R, R1 and CuP, cell R bare on basal half and cell BM almost entirely bare with microtrichia apically. Alula broad, microtrichose. Legs: dark brown except pro- and mesofemora yellowish on apical half, pro- and mesotibiae yellowish and the metafemur-metatibial articulation yellow, yellow and black pilose; metacoxa with a pile tuft at posteromedial apical angle.

Abdomen: elliptic, wide and flat, unmargined. Dorsum mainly black with yellow markings on 2nd to 4th terga, black pilose dorsally and laterally except 1st tergum entirely yellow pilose, 2nd tergum yellow pilose except on dorsal black areas and 3rd tergum yellow pilose on anterior half on lateral margins and dorsally on yellow maculae; 1st tergum black, silvery pollinose; 2nd tergum black with 2 submedial round yellow maculae, silvery pollinose on anterior half; 3rd tergum black with anterior broad (about 4/5 of tergum length) yellow fascia emarginated posteromedially, not reaching lateral margins; 4th tergum similar to 3rd but fascia narrower (about 1/2 of tergum lenght) and emargination forming medialblack vittate macula not reaching anterior margin; 5th tergum black, small, difficult to see on dorsal view; 1st sterna black; 2nd sterna yellow with medial black vita; 3rd sterna yellow with lateral black margins; 4thsterna as 4th tergum; genitalia black, black pilose.

GenBank accession number for this species are: protein-coding COI gene (EF127340), rRNA 28S gene (EF127422) and 18S gene (EU431556).

Xanthandrus has been considered member of the tribe Bacchini sensu lato, although some phylogenetic analysis suggest that Baccha is the only memeber of Bacchini and the other genera commonly related to them should be included in the tribe Melanostomini. Rotheray and Gilbert (1989, 1999) included Melanostoma and Xanthandrus, which, in their analysis, were isolated from the other genera of the ‘‘traditional’’ Bacchini by the tribe Syrphini. These authors also suggested the tribe Melanostomini with only Melanostoma and Xanthandrus as Palaearctic members.

Adults visit flowers of umbellifers; Arbutus unedo, Filipendula, Juncus, Leontodon, Lonicera, Mentha aquatica, Rosa, Rubus, Succisa (Speight 2010).

The larvae are known to predate aphids (Aphididae), Psyllidae, larvae of Coleoptera and Hymenoptera, and the caterpillars of various species of Lepidoptera (see Rojo et al. 2003), both on trees and low-growing plants. They are also recognised predators of the caterpillars of the pine processionary moths (Thaumetopoea pityocampa).

The flight period for European individuals is from May to October (April to November in southern Europe), with no clear period of peak occurrence (Speight 2010).

Widespread Palaeractic species ranging from the Faroes and southern Norway south to Iberia; from Ireland eastwards through central and southern Europe to Russia and the Caucasus and on to the Pacific coast; Japan and Formosa (Speight 2010).

Adults inhabitat clearings, tracksides etc., especially where there is a thick understorey of shrubs and young trees; settles on foliage of shrubs etc.; males hover at 3 - 5 metres (Speight 2010).

Preferred environment: forest, deciduous, broad-leaved evergreen and coniferous; Fagus, Quercus, and Pinus forest and scrub (Speight 2010).

Larva is described and figured by Dusek and Laska (1967) and illustrated in colour and distinguished from larvae of related genera in the keys provided by Rotheray (1993).