Macrostomus trifidus, Rafael & Marques, 2019

Rafael, José Albertino & Marques, Dayse Willkenia Almeida, 2019, Five new species of Macrostomus Wiedemann and a checklist of Empididae (s. str.) (Diptera) from Bolivia, Zootaxa 4567 (2), pp. 251-275 : 267-269

Macrostomus trifidus sp. nov.

( Figs 11 A–O, 12A–E)

urn:lsid:zoobank.org:act:809DA5CB-62C5-4153-873D-8097436197E1

Diagnosis. Thorax shiny yellow with scutellum and mediotergite brown, gray-yellow pruinosity denser on disc of scutum and on scutellum. Wing brown, infuscation darker along costal and r 1 cells and apex of cell r 2+3. Tergite 8 elongate distally, basally more sclerotized with a sclerotized protuberance at base of the projection connecting with mesial cercal bridge of anterior cercus. Sternite 8 with shallow basal medial sinus, with saddle-shaped posterodorsal protuberance. Epandrium with longer setae posteriorly and mainly on posterior lobe. Anterior cercus multilobate, with few longer setae posterodorsally; posterior cercus trifid, all branch yellowish, inwardly curved; ventral projection of cercus downwardly directed, horizontally placed distally when viewed anteriorly or posteriorly, glabrous and not touching each other. Hypandrium well sclerotized, same width throughout, with a hook distally.

Description. Holotype ♂ ( Fig. 11A ). Body length 3.3 mm; wing length 3.8 mm. Head narrowly dichoptic. Frons shiny black, slightly narrower than anterior ocellus width. One pair of proclinate ocellar setae. Face slightly narrower than frons width. Postcranium shiny black, entirely and sparsely gray pruinose. Inner vertical seta stouter than outer vertical seta, latter subequal in length to uniseriate postocular row of setae; 2 pairs of dorsal occipital setae. Gena with 2 setae and postgena with 1 weak seta. Antenna velvety black with postpedicel short pubescent. Proboscis dark brown with median third yellow and apical 2/3 of labellum yellow. Palpus black. Thorax shiny yellow with scutellum and mediotergite brown; scutum gray-yellow pruinose posteriorly and on scutellum. Thoracic chaetotaxy: 3 antepronotals; 1 postpronotal stout and 2 minutes; 3–4 dorsocentral setae; 1 presutural supra-alar; 0 postsutural supra-alar; 1 postalar; 4 proepisternals weak; 1 notopleural stout, 1 weak; 2 pairs of scutellars, the outer pair weaker; 4 laterotergitals. Legs shiny yellow with apex of fore and mid tarsi, distal 1/3 of hind femur, entire hind tibia and tarsus brown to black. Hind femur slightly clavate. Legs longer setae: hind femur with 1 slightly stouter anteroventral seta; hind tibia with 5 longer dorsal setae being with one at basal fourth, one near middle and three along distal third; hind tarsomere 1 with 1 longer median dorsal seta. Wing ( Fig. 11A ) brown infuscated, darker along costal and r 1 cells and apex of cell r 2+3. Veins M 1, M 2 and CuA+CuP weakly evanescent distally. Last section of vein M 4 slightly longer than posterior length of elongate and blunt cell dm. Anal lobe very narrow. Halter light yellow. Abdomen shiny black. Tergite 1–2 with longer setae posteriorly. Tergite 8 in lateral view ( Figs 11B, D ) curved, with sclerotized protuberance at base of projection connecting with mesial cercal bridge of anterior cercus; in dorsal view ( Fig. 11C ) distally with elongate projection (setae broken on projection); basally more sclerotized with deep basal cleft. Sternite 8 ( Figs 11D, E ) with shallow basal medial sinus, with saddle-shaped posterodorsal protuberance. Tergite 8 and sternite 8 strongly connected anteriorly. Epandrium ( Figs 11F, G ) with very small anterodorsal excision and very small anteroventral excision; longer setae posteriorly and mainly on posterior lobe; anterior and posterior lobes of same length; epandrium in posterior view ( Fig. 11G ) with stout protuberance mesially and several yellow distal short setae posterodorsally. Anterior cercus well sclerotized, upwardly directed, multilobate, with few longer setae posterodorsally; when viewed anteriorly ( Figs 11H, K ) cercal bridge V-shaped, fused medially and ventrally. Median cercus ( Fig. 11I ) inverted C-shaped, with elongate setae, less sclerotized distally. Posterior cercus ( Fig. 11J ) trifid, all branches yellow, inwardly curved, apical two setose. Ventral projection of cercus ( Fig. 11K ) downwardly directed, horizontally placed distally when viewed anteriorly or posteriorly, glabrous and not touching each other. Dorsal lobe of hypoproct ( Fig. 11K ) larger with longer setae than narrower ventral lobe. Hypandrium ( Figs 11M, N ) well sclerotized, same width throughout, with hook distally, longer setae restricted to posterior median third. Ejaculatory apodeme ( Fig. 11M ) tetralamellar, all lamella subequal. Phallus ( Figs 11M, N ) slightly longer than hypandrium.

Female. Body length 4.1 mm; wing length 3.8 mm. Frons slightly wider than anterior ocellus width. Face narrower than frons width. Wing slightly darker and wider ( Fig. 12A ). Tergite 8 ( Figs 12B, C ) with shallow basal and deeper distal sinus. Sternite 8 ( Figs 12B, D ) with distinct protuberance ventrally; in ventral view with less sclerotized mid-longitudinal stripe from base to middle. Genital fork ( Fig. 12E ) thin, elongated, bifid at apex. Genital chamber membranous.

Geographical records. Bolivia (La Paz).

Type material examined. HOLOTYPE ♂, paratype ♀, on same pin: “ BOLIVIA, La Paz, Rio Beni, San Buenaventura, 270 m ”; “in copula, San Buenaventura , 22.iv. [19]79”; “QR code: NHMUK 010864590 ”; “ Holotype ♂ Paratype ♀ Macrostomus trifidus Rafael & Marques ” ( Fig. 11O ) (NHMUK).

Holotype condition. Good, pinned, double mounted, abdomen dissected, in microvial with glycerin.

Etymology. From the Latin tri = three and - fid = suffix denoting division, which refers to the three digitiform branch of posterior cercus.

Remarks. Characters allowing a well-founded placement are presently not available for M. trifidus sp. nov. It differs remarkably from other known Macrostomus species by the epandrium emitting mesially and porterodorsally a stout protuberance with several distal short setae; by the posterior cercus trifid with each branch digitiform and by the cercal bridge of anterior cercus V-shaped, fused medially and ventrally.

Figures

FIGURE 11. Macrostomus trifidus sp. nov., holotype ♂. A. Habitus, lateral view; B. Apex of abdomen after macerated, lateral view (pieces with white outline); C. Tergite 8, dorsal view; D. Tergite and sternite 8, lateral view; E. Sternite 8, ventral view; F. Epandrium detached, lateral view; G. Epandrium detached, posterior view; H. Terminalia, posterior view; I. Terminalia (epandrium, hypandrium and phallus removed), right lateral view; J. Branchs of posterior cerci, posterolateral view (black arrows indicating the three branchs); K. Detail of cercal bridge of anterior cercus, ventral projection of cercus and dorsal lobe of hypoproct, anterior view; L. Posterior cercus, posterior view; M. Hypandrium, ejaculatory apodeme and phallus, lateral view; N. Hypandrium, posterior view; O. Holotype labels. Scale bars, figures A = 1 mm; B–N = 0.2 mm. Abbreviations: cbrd, cercal bridge of anterior cercus; vpc, ventral projection of cercus; DHyL, Dorsal hypoproctal lobe;

FIGURE 12. Macrostomus trifidus sp. nov., paratype ♀. A. Habitus, lateral view; B. apex of abdomen, lateral view; C. Tergite 8, 9+10 and cerci, dorsal view; D. Sternite 8, ventral view; E. genital fork and genital chamber, ventral view. Scale bars, figures A = 1 mm; B–E = 0.2 mm.