Orthonevra theta Thompson, 2024

Miranda, Gil F. G., Soares, Matheus M. M. & Thompson, Christian, 2024, The Neotropical Orthonevra Macquart, 1829 (Diptera: Syrphidae), Zootaxa 5484 (1), pp. 1-78 : 67-70

Orthonevra theta Thompson , Miranda & Soares sp. nov.

98-1. Thompson 2006: 21 (key reference)

Fig. 37 . Map: Fig. 40

Diagnosis. The posteriorly fused vittae on the scutum are only found in another species, O. roseae , and O. theta can be promptly distinguished from the former by the straight medial vitta on the eye.

Description. MALE. Head ( Fig. 37a, b, d ): metallic blue-green, face with slight convexity in profile and ventral ¼ slightly produced anteriorly as a very weak convexity, weakly regulose except on ventral ¼ and wide medial area, shiny, pile white and not scale-like; with white microtrichose elongate subtriangular macula laterally, positioned immediately ventral to antennal base and separated from it. Scape yellow, pedicel dark with slight metallic reflections and 2.5 × longer than scape, post-pedicel oval elongate and as long as pedicel; pile on pedicel black. Mala produced apico-ventrally, with weak regulae. Gena shiny, smooth, and with white pile. Frontal triangle metallic-blue, regulose but smooth around and on lunule, bare except for white pile anterior to eye contiguity and laterally following the eye margin. Vertical triangle isosceles triangle-shaped and very long, 4 × longer than eye contiguity, metallic-bluish green, bare but with very few, inconspicuous black pile on ocellar triangle and posterior to it, with a few regulae anterior to anterior ocellus; ocellar triangle more matte than vertical triangle, equilateral triangle-shaped. Occiput not visible laterally on dorsal ½, ventral ½ homogeneously covered in white microtrichia which extends until dorsal to gena, with a row of very short black pile, which becomes longer and white on ventral 1/5. Eyes holoptic; with anterior, sub-anterior (slightly sinuous ventrally) and medial straight vittae, and only with short fragments of a medial fascia, anterior and sub-anterior vittae join dorsally and ventrally, eyes darker on postero-ventral margin.

Thorax ( Fig. 37a, b ): metallic bluish-green, pile very short and inconspicuous, white, appressed and sparsely distributed, slightly longer on notopleuron; scutum with four dark matte vittae, medial pair fused on posterior ¼, and with a short narrow lateral vittate macula posterior to transverse sulcus; scutellum mostly matte dark but metallic-green on margins, with a sub-basal and sub-apical transversal linear depression, bare but tubercles of pile insertions present. Pleuron wholly metallic, smooth on proepimeron and dorso-medial anepimeron, remaining with a coarse texture, with some white microtrichia posteriorly to anterior spiracle, with white pile on antepronotum (and longer anteriorly to anterior spiracle), proepisternum, posterior anepisternum, anterior anepimeron, dorsal and ventral patches on katepisternum, katatergum, and metasternum. Dorsal lobe of calypter white with long white marginal pile, ventral lobe similar but pile 3 × longer than dorsal pile. Plumule white. Halter yellowish.

Legs ( Fig. 37b ): dark with metallic reflections, except apical tarsomeres just dark without reflection; pale on apex of femur, basal 1/3 of tibia (1/2 on mesotibia), and first two tarsomeres (dark on most of dorsal surface of metabasitarsomere). Legs covered with short white pile, longer on coxa, apex of mesotibia and mesotarsomeres with ventral black setulae, metafemur with short black setulae ventrally.

Wing ( Fig. 37b ): R2+3 abruptly bent towards C at the end, ending distinctly basally to the level where M1 meets R4+5; with a narrow dark vitta from bend on R2+3 to where M1 meets R4+5, and with fasciate macula in r4+5, and apex of r2+3 slightly darkened ( Fig. 37e , specimen might have had more markings), mostly microtrichose but with narrow bare areas on middle of r, bm and baso-anteriorly on cua immediately posterior to pseudovein; basicosta with sparse appressed white pile, without prominent setae apically. Alula slightly wider than cell c.

Abdomen ( Fig. 37b, c ): metallic light blue but matte black medially until tergum 4, remaining segment wholly metallic, pile sockets as small protuberances, pile white, appressed and short, but longer on baso-lateral ½ of tergum 2; sterna metallic, with similar pilosity but slightly longer; sternum 4 right side distinctly extended.

Genitalia ( Fig. 37f, g ): hypandrium rectangular and short; postgonites curving dorsally and with a few laminae laterally, with very few pile apically; phallus with similar height throughout its extension (not narrowing posteriorly), with a small beak-like apex but flanked by large laminae, with an expansion dorso-medially, and basal tubular process as a wide ventral opening with a short lip apically ( Fig. 37f ).

FEMALE. No females recorded.

Length. Body 3.97mm (n=1); wing 3.06mm (n=1).

Distribution. Ecuador ( Fig. 40 ).

Altitudinal range. 1880m.

Etymology. The specific epithet represents the letter Θ from the Greek alphabet, which alludes to the shape of the eye markings when viewed from the front. It should be treated as a noun in apposition.

Comments. Epandrium of the specimen was lost.

Type material examined: ECUADOR. Napo, Lago Agrio [ca 0°27’52.6”S 77°52’57.6”W], 8 km west of, Malaise trap, 28.viii.1975, Langley & Cohen (male holotype theta USNM, USNM01492695) .

Figures

FIGURE 37. Orthonevra theta sp. nov., male. a–e. Habitus: a. Dorsal. b. Lateral. c. Abdomen, apex, ventral view. d. Head, oblique lateral view. e. Wing, apex. f–g. Genitalia: f. Hypandrium, lateral view. g. Hypandrium, oblique dorsal view. Abbreviations: ave: anterior vitta (eye); btm: metabasitarsomere; btp: basal tubular process; mve: medial vitta (eye); M1: vein M1; pd: pedicel; pg: postgonite; ph: phallus; ppd: post-pedicel; R2+3: vein R2+3; R4+5: vein R4+5; sav: sub-anterior vitta; s4 pj: lobular projection of sternum 4.

FIGURE 40. Distribution map for Orthonevra gewgaw (Hull, 1941), O. gouletmasnerorum sp. nov., O. minuosetulata sp. nov., O, nebulosa sp. nov., O. neiae sp. nov., O. neotropica (Shannon, 1925), and O. theta sp. nov.