Hybobathus avittatus, Miranda, 2017

Miranda, Gil Felipe Gonçalves, 2017, Revision of the Hybobathus arx and Pelecinobaccha summa species groups (Diptera: Syrphidae), Zootaxa 4338 (1), pp. 1-43 : 9-11

Hybobathus avittatus sp. nov.

Fig. 3

Description. MALE. Head ( Fig. 3c ). Yellow; face slightly darker dorsal to tubercle, with sparse white microtrichosity, with black pile, absent medially. Gena with white pile. Lunule with central black marking. Frontal triangle with inconspicuous brown vittate spot medially, and with black pile but bare medially. Base of antenna protuberant. Vertical triangle with very sparse white microtrichia, except on ocellar triangle, which is dull black, and on medial area posterior to the ocellar triangle, with several irregular rows of black pile, coalescing into a single row, ending dorsal to the anterior ocellus; ocellar triangle separate by its length from the posterior margin of the head. Eye contiguity shorter than the vertical triangle length. Eye with weak sub-triangular indentation on posterior margin positioned around the level of antennal insertions. Antenna with black pile; postpedicel slightly darker dorsally. Occiput covered by very sparse white microtrichia, with white pile, dorsal 1/3 with one row of flattened pile, ventral 2/3 with 2–3 rows, posterior row with longer pile. Thorax ( Fig. 3a ). Scutum black, but yellow laterally from postpronotum to scutellum; with barely visible white microtrichia on a central, narrow, tapering anteriorly, vitta and a sub-medial pair that tapers posteriorly; pile white and erect, longer on anterior continuous row and laterally from the notopleuron until the postpronotum. Scutellum yellow, with slightly darker medial region, with sparse, very short, black and erect pile, slightly longer baso-laterally; subscutellar fringe mostly absent, except for very few white pile upwardly curved. Pleuron yellow, dark on anterior 1/3 of posterior anepisternum, ventral 1/2 of katepisternum, meron and postero-ventral margin of katatergum; white pilose (proepimeron, anterior and posterior anepisternum, dorsal and ventral katepisternum, with pile patches joining anteriorly, anterior anepimeron, katepimeron and metaepisternum), katatergum with long microtrichia giving it a ‘velvet’ appearance. Plumula very short and pale. Calypter yellow, pile long and pale on margin of the ventral lobe and absent on margin the dorsal lobe. Halter yellow, capitulum orange. Wing ( Fig. 3b ). Light yellow, slightly darker on stigma and medially on cell r1; entirely microtrichose; alula light yellow, convex, basally 1.5 times to apically 3.5 times as broad as c cell, entirely microtrichose. Legs ( Figs 3a & b ). Legs yellow, except light brown on metacoxa, basal 2/3 of metafemur and medial 1/3 of metatibia; pile yellow, slightly longer baso-ventrally on profemur, distinctly longer and black in a posterior row on mesofemur, and black anteriorly on metacoxa, medially on metafemur, and medially on metatibia; metabasitarsomere 1/2 the length of the metatibia. Abdomen ( Fig. 3a ). Mostly dark brown and petiolate, 2.8 times the length of the thorax. Tergite 1 yellow, except for dark brown apical margin, with long, yellow and erect pile, except dark medially, and bare apically; sternite 1 yellow with yellow appressed pile. Tergite 2 long, 6 times longer than smallest width, and wholly yellow, slightly paler baso-laterally; with long, black and erect pile, except shorter and appressed dorsally; sternite 2 mostly bare, with very sparse short inconspicuous black pile. Tergite 3 trapezoidal, slightly longer than apical width and apical margin 2.5 times wider than basal margin, yellow basally and baso-laterally until the middle, and with a very narrow central yellow vitta; pile long, black and appressed; sternite 3 yellow with black and appressed pile. Tergite 4 rectangular, slightly wider than long, with yellow base and baso-lateral 1/2; remaining characteristics as on segment 3. Tergite 5 rectangular short, wider than long, yellow on margins, dark brown medially; remaining characteristics as on 4. Genitalia ( Figs 3d–h ). Cercus with 2 rows on dorso-medial margin and 1–2 rows of much sparser pile towards lateral margin; surstylus sub-triangular, in lateral view, larger at base than on apex, with pile on dorso-basal 2/3, ventral surface covered in sparse setulae except for small bare basal area; subepandrial sclerite sub-rectangular, wider than long, without apical indentation, and with slightly concave basal indentation. Hypandrium oval, in ventral view, ventral notch covering whole ventral surface, with concave basal margin, and with medial-lateral indentations slightly extending dorsally; phallapodeme wholly sclerotized; basiphallus drop-shaped, in ventral view, but basal acute extremity very short, in lateral view almost uniformly of the same height (abruptly tapering basally), distiphallus very slightly sinuous, anterior sclerotized surface tapering apically, with wider membranous area on apex, ventral surface completely membranous, basal sclerotized area extending laterally but not connecting ventrally; postgonite quadrate, shorter than other species from the H. arx group, with baso-ventral extremity extended basally, anterior margin straight but with a small concavity medially, dorsal surface straight, apico-dorsal extremity with very short acute projection, and apico-ventral extremity with long acute projection. with very short pile only baso-ventrally.

FEMALE. Unknown.

Length. Body: 14.8mm; wing: 12mm.

Distribution. Mexico (Chiapas).

Etymology. The specific epithet avittatus (without vittae) refers to the lack of vittate markings on the abdomen and should be treated as an adjective.

Comments. It seems that most of the microtrichosity was obscured dorsally on the type specimen after dissection, but it is still possible to see the common boundaries of its typical distribution in the Hybobathus arx group. This species is readily distinguished from others of this group by the lack of vittae on the abdomen ( Fig. 3a ), and its genitalia, which is unique among the group due specially to its short and sub-triangular surstylus ( Figs 3d & e ) (elongated and sub-oval on other species) and postgonite with abbreviated apico-dorsal extremity ( Fig. 3g ) (extremity more robust on other species).

Type material. HOLOTYPE: Male specimen in good conditions, microtrichosity of scutum obscured, and genitalia dissected, placed in a microtube with glycerin and pinned with the specimen; “ MEXICO: Chiapas, Municipio Teopisca, 5 km W of Teopisca, 1768m 27-XI-1976 D.E. & J.A. Breedlove Cal. Acad. Sci. Coll.” “USNMENT01243063” “ Holotype Hybobathus avittatus Miranda” [red label].

Figures

FIGURE 3. Hybobathus avittatus sp. nov., male, holotype. a. Habitus, dorsal. b. Habitus, lateral. c. Head, frontal. d – h. Genitalia: d. Epandrium, dorsal. e. Epandrium, ventral. f. Hypandrium, ventral. g. Hypandrium, lateral. h. Hypandrium, basiphallus focus, lateral. bph: Basiphallus, ind: Ventro-lateral indentation of the hypandrium, pgt: Postgonite, sscl: Subepandrial sclerite, srs: Surstylus.