Psilota basalis ( Walker, 1858 )

Young, Andrew D., Skevington, Jeffrey H. & Steenis, Wouter Van, 2020, Revision of the Psilota Meigen, 1822 flower flies (Diptera: Syrphidae) of Australia, Zootaxa 4737 (1), pp. 1-127 : 34-36

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Psilota basalis ( Walker, 1858 )


Psilota basalis ( Walker, 1858)

(Species plate: Fig. 12 View FIGURE 12 ; Genitalia: Fig. 41 View FIGURE 41 C–D; Map: Fig. 53A View FIGURE 53 )

Orthonevra basalis Walker, 1858: 97 . Type locality: Aru, Maluku province, Indonesia

Diagnosis: Face shining, with pollinosity restricted to two lateral triangles below antenna. Pleuron shining, free of pollinosity. Pile on anepimeron black, pile on remainder of pleuron white. Wing with an anterior brown vitta starting at stigma and ending in cell R 4+5. Hind leg simple. Tergite 2 with two yellow triangular maculae. Tergite 2 to 4 with posterior margin faintly metallic blue. Body length: 7.8–9.9 mm.

Description: MALE: Head: Head black, face shining blueish-black, with pollinosity only in two lateral triangles below antennae. Face white pilose, frons with mixed black and white pile, vertex black pilose. Scape and pedicel orange, postpedicel dark brown with ventral half orange, oval, approximately twice as long as wide. Eye densely brown pilose. Thorax: Thorax black. Legs mostly black, with extreme apices of fore- and mid femora orange, basal half of fore and mid tibia orange, and first and second more and mid tarsomeres orange. Hind leg entirely black. Hind femur unmodified, with only a few weak, black setulae apicoventrally. Pleuron shining, free of pollinosity. Pile on anepimeron black, pile on remainder of pleuron white. Pile on scutum and scutellum mostly black, with a few white pile posterior to the transverse suture on the scutum. Wing with an anterior brown vitta starting at the stigma and continuing posteriorly through the anterior 1/3 rd of cell R 1, the middle of cell R 2+3, and ending in the middle of cell R 4+5. Cell bm entirely bare, cell cua with a few scattered microtrichia apically, cell br mostly bare, with central crease microtrichose, cell c bare on basal 1/3 rd, cells r 1, r 2+3, and r 4+5 bare basally. Alula bare on basal half. Halter pale yellow. Calypter pale yellow. Abdomen: Abdomen mostly black. Tergites 2 with two triangular yellow spots, ranging from half the length of the tergite to almost the entire length of the tergite. Tergites 2 to 4 with the posterior rim faintly metallic blue. Tergites shining, free of pollinosity. Lateral sides of tergites 1 and 2, maculae on tergite 2, and apical half of tergite 4 pale pilose, otherwise tergites black pilose. Sternite 2 yellow, other sternites black. All sternites pale pilose. Genitalia: Epandrium very compact, about 1.5 times as tall as long. Cercus blunt, semicircular. Outer lobe of surstylus inserted at top of inner lobe, thick and curved smoothly downwards over its entire length. Inner lobe of surstylus short, swollen at base, sharply constricted at midlength, approximately 3.5 times as long as wide (at base), and rounded at apex. Inner lobe of surstylus also with a medial projection on the dorsal half of the inner surface running the length of the surstylus. Tip of the inner lobe of surstylus curved medially on the dorsal surface, forming a second medial projection. Phallapodeme with a downwards facing projection on the ventral surface. Postgonite elongate, extending well beyond the tip of the phallus.

FEMALE: Identical except for normal sexual dimorphism.

Specimens examined: LECTOTYPE: INDONESIA: Maluku Province: Labels read: “ Orthonevra basalis , wlk”, “basalis”, “ Holotype [red circular label]”, “Aru” Jeff _ Skevington _ Specimen _45632. (1♀, BMNH). Other ma- terial: AUSTRALIA: Queensland: 14 km W by N of Hope Vale Missn., -15.160000 144.590000, at light, 8.X.1980; 9.V.1981, coll. D.H. Colless, USNM _ENT_00249846-00249847 (2♂♂ USNM). GoogleMaps

Discussion: This species was originally described from a female specimen collected in the Aru Islands Regency (Maluku Province, Indonesia). This lectotype female is in the BMNH and is labelled “ Orthonevra basalis , wlk”, “basalis”, “ Holotype [red circular label]”, “Aru”, and “Jeff Skevington Specimen #45632”. The last label as added by the author ADY as a unique identifier for databasing purposes. This specimen is herewith designated lectotype and has been so labelled.

The above description is the first of the male of this species and the first record of this species in Australia. This male is assumed to be the conspecific with the Indonesian female lectotype due to the distinct brown vitta on the wing and the faint metallic blue markings on the abdomen, which match the lectotype very well.


Smithsonian Institution, National Museum of Natural History














Psilota basalis ( Walker, 1858 )

Young, Andrew D., Skevington, Jeffrey H. & Steenis, Wouter Van 2020

Orthonevra basalis Walker, 1858: 97

Walker, F. 1858: 97