Rhopalosyrphus (s.l.) oreokawensis Reemer

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 118-119

Rhopalosyrphus (s.l.) oreokawensis Reemer sp. n. Figs 347-351, 355

Type specimens.

HOLOTYPE. Adult male. FRENCH GUYANA. Label 1: "FRENCH GUYANA / Kaw Mountains / 04°32.893"N-52°10.245"W / 27.XI.2002. leg. V. Soon". Coll. RMNH.

Diagnosis.

Within Rhopalosyrphus s.l. this species is singular because of its short antenna (slightly shorter than distance between antennal fossa and anterior oral margin) and the shape of the ventral part of the face.

Description (based on holotype).

Adult male. Body size: 13 mm.

Head. Face occupying a little more than 1/3 of head width in frontal view; black; entirely white pilose; ventral part of face anteriad of oral margin with lateral bulges, medially separated by shallow, smooth sulcus. Gena black, white pilose. Lateral oral margins slightly produced. Frons, vertex and occiput black; white pilose, except for sparse black pile on frons. Eye bare. Antennal fossa about as high as wide. Antenna brown; antennal ratio approximately as 4:1:3; slightly shorter than distance between antennal fossa and anterior oral margin.

Thorax. Black. Mesoscutum black pilose, except for fasciae of white pile along anterior margin and transverse suture, and patches of white pile posterolaterally. Postpronotum and postalar callus white pilose. Scutellum semicircular; white pilose; with small calcars with mutual distance about equal to 1/4 of width of scutellum. Anepisternum with deep sulcus; black pilose anterodorsally, white pilose posteriorly, widely bare in between. Anepimeron entirely white pilose. Katepisternum white pilose dorsally, bare ventrally. Katatergum long microtrichose, anatergum short microtrichose. Calypter yellow. Halter brown.

Wing: Hyaline, but infuscated at apical 1/2 of cell c, cell sc, around vein r-m, around vein R4+5 and posterior appendix of that vein, around vein dm-cu and around bm-cu. Microtrichose, except bare on cell bc, basal 1/2 of cell c, basal 1/2 of cell r1, basal 1/3 of cell r2+3, posterobasal 1/4 of cell r4+5, entirely bare on cell br, basal 9/10 of cell bm, basal 2/3 of cell cup, and entirely on alula.

Legs: Front and mid legs orange brown, except mid femur blackish brown on basal 2/5; white pilose, except front tibia black pilose on apicodorsal 1/4, tarsi dorsally black pilose and mid femur on apical 1/2 posterodorsally with sparse bristle-like pile among long white pile. Hind leg black, except basal 1/2 of tibia and apical four tarsomeres dark brown; white pilose, except tarsus dorsally black pilose and femur on apical 1/5 with row of short, black, bristle-like pile anteroventrally; femur swollen: about 2.5 times as wide as mid femur. Front coxa brown, mid and hind coxae black; all coxae white pilose. Front and mid trochanters brown, hind trochanter black; all trochanters white pilose.

Abdomen. Constricted, narrower than thorax, with narrowest point at transition between segments 2 and 3. Tergites black, except tergite 2 with pair of large elongate yellow maculae on basal 3/5 and narrowly yellow along posterior margin, and tergite 3 vaguely brownish yellow along anterior margin. Tergite 1 white pilose. Tergite 2 short black pilose, except with long white pile anterolaterally and with thick, appressed white pile along posterior margin. Tergite 3 short black pilose, except for medially interrupted fasciae of thick, appressed white pile along anterior and posterior margins. Tergite 4 yellow pilose on lateral 1/4 and posterior 3/5, black pilose anteromedially and on narrow median vitta on posterior 3/5. Sternite 1 black; bare. Sternite 2 yellow except black along posterior margin; with sparse long white pile. Sternite 3 yellow at anterior 3/5, black posteriorly; short black pilose on posterior 1/2 to 3/5, long, thick white pilose along posterior and posterolateral margins. Sternite 4 brown; black pilose medially, yellow pilose laterally. Male genitalia as in Fig. 355.

Female. Unknown.

Etymology.

The specific epithet (noun in the genitive case) is composed of the Greek oreos (mountain) and Kaw, the name of the French Guyanan mountain region in which the species was found.

Notes.

This species is very aberrant from other known species of Rhopalosyrphus because of the short antenna, the straight facial profile, the bare katepisternum and the long and slender second abdominal segment. These characters suggest that the species may not belong in Rhopalosyrphus . However, it is certainly related to that genus, considering the structure of the male genitalia and the constricted abdomen. If a new genus were to be erected for this species, more evidence on its phylogenetic affinities to Rhopalosyrphus and other related genera (e.g. Pseudomicrodon ) should be available.