Toxomerus basalis (Walker)

Mengual, Ximo, 2011, Black-tie dress code: two new species of the genus Toxomerus (Diptera, Syrphidae), ZooKeys 140, pp. 1-26 : 8

Toxomerus basalis (Walker)

Syrphus basalis Walker 1836: 345. Type Locality: Brazil, St. Paul Island [HT ♂, BMNH].

Syrphus portius Walker 1852: 239. Type Locality: Brazil [T ♂, BMNH].

Mesogramma rhea Hull 1949: 228. Type Locality: Brazil [ST ♂, AMNH].

Mesogramma harlequina Hull 1951: 69. Type Locality: Brazil, São Paulo [HT ♀, MZSP].

Differential diagnosis.

Species with yellow face. Scutum black, bronze pollinose with a medial bluish pollinose vitta, yellow pilose; postpronotum yellow and notopleuron black with a small yellow macula posteriorly. Metacoxa yellow and metafemur black, yellow on basal 1/4-1/3. Abdomen shiny black with a medial black pollinose vitta on terga 2 to 5; terga 2, 3, 4 and 5 with triangular yellow macula on anterior 1/2-2/3 of lateral margins (see Borges and Couri 2009: 17, Figs 22 and 23). Diffuse, dark yellow markings might be observed in some pale forms in the center of terga 3 to 5. Toxomerus basalis has the wing partially bare, with costal cell bare on basal half, cell R1 bare basal to bifurcation RS, cell R bare basal to bifurcation RS and vein bm-cu, cell BM bare on anterior margin and on basal half of posterior margin, and cell CuP bare on anterior margin.

Length

(4): body, 6.0-6.5 (6.3) mm; wing, 5.0-5.2 (5.1) mm.

Distribution.

Southeastern Brazil.

Material examined.

3♂ 1♀.

Remarks.

The illustration of Mesogramma portia in Hull (1943: 31, Fig. 17) has two submedial short yellow vittae on terga 3, 4 and 5, forming a U-shaped macula on tergum 5. These submedial yellow vittae are at both sides of the medial black pollinose vitta. This illustration refers to a paler form of Toxomerus basalis .