Orthonevra quadristriata ( Shannon & Aubertin, 1933 )

Miranda, Gil F. G., Soares, Matheus M. M. & Thompson, Christian, 2024, The Neotropical Orthonevra Macquart, 1829 (Diptera: Syrphidae), Zootaxa 5484 (1), pp. 1-78 : 57-59

Orthonevra quadristriata ( Shannon & Aubertin, 1933)

Chrysogaster quadristriata Shannon & Aubertin 1933: 140 . Type-locality:Argentina, Bariloche [ca 41°08'49.0"S 71°20'20.9"W] (HT male USNM). Stuardo 1946: 125 (catalog citation); Fluke 1957: 50 (catalog citation); Etcheverry 1963: 28 (republished original description, synonymy).

Orthonevra quadristriata . Thompson et al. 1976: 91 (catalog citation); Thompson 2006: 121 (catalog citation), 21 (key reference).

Fig. 31 . Map: Fig. 39

Redescription. MALE. Head ( Fig. 31a–c ): metallic blue, face wide, almost straight in profile and ventral ¼ produced anteriorly as a strong convexity, regulose except for smooth ventral 1/3, shiny, with white pile but sparse ventrally; with large white microtrichose subtriangular macula laterally, positioned immediately ventral to antennal base and almost reaching it. Antenna dark, except pedicel pale apically and post-pedicel pale baso-ventrally; pedicel short but slightly longer than scape, postpedicel with mostly straight dorsal surface and convex ventral surface, with a shallow concavity pre-apically on dorsal surface, 2.5 × longer than the pedicel. Mala greatly produced apico-ventrally, smooth. Gena shiny, smooth, and with white pile. Frontal triangle shiny, rugose, uniformly covered with erect and sub-appressed white pile, without median longitudinal groove. Vertical triangle equilateral triangle-shaped, dark blue metallic, uniformly covered with long, erect, black pile on ocellar triangle and posterior to it. Occiput visible laterally on dorsal 1/3, although narrow, homogeneously covered in white microtrichia, and with one row of white pile. Eyes dichoptic; with a slightly sinuous sub-anterior vitta and a medial fascia extending from the posterior margin until the sub-anterior vitta.

Thorax ( Fig. 31a, b ): metallic blue, homogeneously covered with densely distributed, short, black pile, longer and white on notopleuron; scutum with four complete separate dark matte vittae, with a short narrow lateral vittate macula posterior to transverse sulcus; scutellum metallic blue and somewhat darker medially, slightly depressed on apical margin, covered with white pile. Pleuron metallic blue, mostly smooth with few areas with fine microsculpturing, with short white pile on proepisternum, proepimeron, posterior anepisternum, anteriorly on anepimeron, very few on a dorsal and ventral patch on katepisternum, and on katatergum, metasternum bare. Calypter white with long white marginal pile. Plumule white. Halter yellowish.

Legs ( Fig. 31a, b ): metallic dark, except all tibiae pale. Legs covered with white pile, longer ventrally on femora, apex of mesotibia and mesotarsomeres with ventral black setulae, metafemur with ventral surface covered in black setulae.

Wing ( Fig. 31 a, b ): hyaline, without vittate maculation but with some fasciate maculae in cells r2+3, r4+5 and dm; stem vein and vein C paler until crossvein h; vein R2+3 ends on C apically to the level of the intersection of M1 with R4+5, vein M1 recurrent; wholly microtrichose; basicosta with dense appressed pale pile, with two more prominent (apical moreso) pale setae apically. Alula large, 2.5 × the width of the cell c.

Abdomen ( Fig. 31a, b ): metallic blue, but with large matte black area medially from terga 1 to 4; pile white, appressed, longer baso-laterally on tergum 2; sterna dark metallic, with longer white appressed pile, erect on sternum 2; sternum 4 with apical margin straight.

Genitalia ( Fig. 31e–j ): surstylus straight, mostly narrow but base extends ventrally,base with a small protuberance dorsally, ending on a small acute apex, mostly with long pile but bare on base and apico-dorsal 1/5 ( Fig. 31e–g ); subepandrial sclerite arms wide; cercus slightly oval, with an unpigmented medial division ( Fig. 31e ), and not extended as in other Orthonevra . Hypandrium basal 2/3 oval, apical 1/3 straight, covering the phallus as a sheath, membranous dorsally but apex separated into two lobes ( Fig. 31j ), with anterior ventral notch flanked by short acute laminae that leave the notch as a short ventral slit ( Fig. 31h, i ); postgonites widening towards apex and with medial margin with irregular serration, with short and wide peduncle and rising dorsal to the ventral notch laminae ( Fig. 31h–j ); phallus beak-shaped apically, with two ventro-medial prongs directed dorsally (directed ventrally in all other Orthonevra ) anterior to basal tubular process, basal tubular process short and medially positioned.

FEMALE. No females recorded.

Length. Body 4.92mm (n=1), wing 3.78mm (n=1).

Distribution. Argentina ( Fig. 39 ).

Altitudinal range. 1150m.

Comments. This is the first time that the male genitalia of O. quadristriata is depicted. Clearly close to O. chilensis but with eyes more clearly dichoptic, ventral ¼ of face featuring a stronger convexity and distinct male genitalia (see key for other distinct characters). The male cercus resembles that found in the pictipennis group of Sedman (1966a), with the clear division of the cercus by an unpigmented line (a characteristic not found in other species from the current study); furthermore, the baso-ventral extension of the cerci is similar to O. pictipennis (Loew) .

This is the Orthonevra species with the southernmost record among the material studied. The female specimens that Shannon & Aubertin (1933) mention in the description (“…from the following localities: Argentina, L. Correntoso and Bariloche ; Chile, Perales”) were not found in the USNM collection, regardless, those authors found it “impossible to decide whether they are all the same species, and whether they are conspecific with the male”, so we assume that they were not conspecific with the type.

Since the original description of this species, there were no other confirmed records of O. quadristriata in the literature or online (the record for Colombia at CEUA was a misidentification).

Type material examined: ARGENTINA. Rio Negro, Bariloche [ca 41’08'4”.0"S71’20'2”.9"W], “AgrNov1926” [sic], ??. xi.1926, R. & E. Shannon (male holotype quadristriata USNM, USNMENT 01754724) .

Figures

FIGURE 31. Orthonevra quadristriata (Shannon & Aubertin, 1933), male, holotype. a. Habitus dorsal. b. Habitus lateral. c. Head, oblique lateral view. d. Labels. e–j. Genitalia: e. Epandrium, lateral view. f. Epandrium, oblique lateral view, medial surface of right surstylus. g. Epandrium, dorsal view. h. Hypandrium, oblique lateral view. i. Hypandrium, ventral view. j. Hypandrium, dorsal view. Abbreviations: btp: basal tubular process; cerc: cercus; hypl: ventral lamina of the hypandrium; lba: apical lobe of the hypandrium; pg: postgonite; ph: phallus; sur: surstylus; umd: unpigmented medial division.

FIGURE 39. Distribution map for Orthonevra argentina (Brèthes, 1922), O. batman sp. nov., O. chilensis Thompson, 1999, O. cthulhu sp. nov., O. quadristriata (Shannon & Aubertin, 1933), O. roseae sp. nov., O. shannoni (Curran, 1926), and O. thompsoni sp. nov.