Macrostomus unilineatus, Rafael & Marques, 2021

Rafael, José Albertino & Marques, Dayse Willkenia A., 2021, Four new species of Macrostomus Wiedemann and a checklist of Empididae s. str (Diptera) from Peru, Zootaxa 4981 (3), pp. 506-530 : 523-524

Macrostomus unilineatus sp. nov.

( Figs 13A–P , 14A–D )

http://zoobank.org/ urn:lsid:zoobank.org:act:71FB5F63-EAE2-4443-992D-6BB262A4CFEF

Diagnosis. Male. Thorax shiny yellow with a mid-longitudinal black stripe from pronotum to scutellum, between row of dorsocentral setae; hind tibia with tuft of longer anterodorsal and dorsal setae along distal third; cell bm clearer than adjacent cells; male tergite 8 with a distinct subapical neck in lateral view, basally more sclerotized with deep basal cleft; epandrium with posterodorsal lobe higher than anterodorsal lobe, emitting mesially and posterodorsally a stout and short protuberance with several distal short setae; posterior cercus trifid, all branches yellowish, inwardly curved; ventral projection of cercus downward directed and fused to each other; hypandrium with a distinct membranous area, apex with an elongate pair of less sclerotized spoon-shaped upwardly directed projections.

Description. Holotype ♂ ( Fig. 13A ). Body length 4.6 mm; wing length 5.3 mm. Head narrowly dichoptic ( Fig. 13B ). Frons shiny black, as wide as width of anterior ocellus. One pair of proclinate ocellar setae. Face slightly narrower than frons width. Postcranium shiny black, sparsely gray pruinose on ventral half, dorsally with 3 pairs of occipital setae. Inner vertical seta stouter than outer vertical seta, latter subequal in length to uniseriate postocular row of setae. Gena with 5 setae and postgena with 2 weak setae. Antenna velvety black with postpedicel short setulose ( Fig. 13B ). Proboscis around 2X longer than head, dark brown with median third yellow and apical 2/3 of labellum yellow. Palpus black. Thorax ( Figs 13A–B ) mainly shiny yellow with mid-longitudinal black stripe between dorsocentral setae, from pronotum to posterior margin of mesonotum, wider posteriorly; disc of scutum brown pruinose. Scutellum dark brown to black, brown pruinose. Thoracic chaetotaxy: 4–5 antepronotals; 1 postpronotal stout, 1 minute; 4 dorsocentrals, posterior pair longer, two median pairs approximate to each other; 1 presutural supra-alar; 1 postsutural supra-alar; 1 postalar; 1 proepisternal weak; 1 notopleural stout, 1 weak; 2 pairs of scutellars, outer pair weaker; 5 laterotergitals with 3 setae of anterior row stouter. Legs ( Fig. 13A ) shiny yellow with apex of fore tibia, apex of mid femur and tibia and hind leg from distal half of femur brown. Fore tarsus with tarsomere 1 brown, tarsomeres 2–4 bicolored, brown, and white; mid and hind tarsi brown. Hind femur slightly clavate. Legs longer setae: fore tibia with 1 anteroventral and 1 posteroventral at apex; mid tibia with 2 dorsals, being one near middle and one near apex; hind tibia with tuft of longer anterodorsal and dorsal setae along distal third; hind tarsomere 1 with 1 dorsal sub-basal. Wing ( Fig. 13A ) distinctly brown infuscate along costal margin reaching apex of cell r 4+5; veins M 1, M 2 and CuA+CuP somewhat evanescent distally. Distal section of vein M 4 slightly longer than vein dmm; cell bm clearer than adjacent cells. Cell dm somewhat projected ( Fig. 13A ). Abdomen ( Fig. 13A ) shiny black, with terminalia densely setose ( Fig. 13C ). Tergite 8 in dorsal view ( Fig. 13D ) with elongate projection distally, notched medially; basally more sclerotized with deep basal cleft; in lateral view ( Fig. 13E ) with pelican-shaped beak. Sternite 8 ( Fig. 13E ) connected anterodorsally with tergite 8; in ventral view with distinct anterior sinus and posterodorsal saddle-shaped protuberance ( Fig. 13F ). Epandrium ( Fig. 13G ) with inconspicuous anterodorsal cleft and shallow anteroventral excision; posterodorsal lobe higher than anterodorsal lobe; with distinct inward, setose posterodorsal lobe in posterior view ( Fig. 13H ). Anterior cercus in lateral view ( Fig. 13I ) upward directed, T-shaped with longer posterior setae, with stout mesial process of anterior cercus fused to each other ( Fig. 13L ); cercal bridge with small protuberance dorsally ( Fig. 13K ) and medially with hemi-cordiform plate; this plate, in lateral view, with ventral expansion forming 90º angle ( Fig. 13I ). Median cercus ( Fig. 13I ) distinctly acuminate with longer dorsal setae, besides small posterior protuberance with distal seta. Posterior cercus ( Figs 13L, M ) inwardly curved emitting three branches, each branch with yellow distal setae ( Figs 13L, M ). Ventral projection of cercus ( Fig. 13M ) somewhat sinuose, bowl-shaped, fused to each other ventrally. Dorsal hypoproctal lobe larger than ventral one, with longer setae ( Fig. 13M ). Hypandrium wide with distinct membranous area ( Fig. 13N ), with longer posterior setae, basal setae uniseriate ( Fig. 13O ); apex with subapical paired elongate projection less sclerotized, spoon-shaped and upwardly directed ( Figs 13N–O ). Ejaculatory apodeme ( Fig. 13N ) tetralamellar, all lamellae subequal in length. Phallus slightly longer than hypandrium.

Female. Paratype ♀ ( Fig. 14A ). Body length 4.7 mm; wing length 5.4 mm. Frons slightly wider than width of anterior ocellus. Face slightly narrower than frons, gray pruinose; fore tarsus brown to black; hind tibia with 2 dorsal setae along distal third; hind tarsus without longer dorsal setae; wing slightly wider. Tergite 8 ( Figs 14B, C ) with basal and distal sinus. Tergite 9+10 and sternite 10 with basal excision. Cercus cylindrical. Sternite 8 ( Figs 14B–C ) with deep lateral, less sclerotized area, apex somewhat rounded. Genital fork ( Fig. 14D ) wide with mid-distal cleft. Genital chamber membranous with two small, weakly sclerotized plates.

Geographical record. Peru (Junin).

Type Material examined. HOLOTYPE ♂, PARATYPE ♀, same pin, labelled: “ PERU, Junin, Oxapampa, 1700 m ” / “in copula, Oxapampa , 6.iii.[19]79” / “QR code: NHMUK 010864610” / “ Holotype ♂, Paratype ♀, M. unilineatus Rafael & Marques ” ( Fig. 13P ) ( NHMUK). PARATYPE: Same data as holotype, except 8.iii.[19]79 / “QR code: NHMUK 010864611” / “ Paratype ♀ Macrostomus unilineatus Rafael & Marques ” (1 ♀, NHMUK) .

Holotype condition. Pinned, double mounted. Wing with small broken piece between veins M 4 and CuA+CuP. Abdomen dissected, stored in microvial with glycerin.

Etymology. From the Latin uni = one and lineatus = of a line, which refers to the mid-longitudinal black stripe on mesonotum.

Remarks. Characters allowing a well-founded species-group placement are presently not available for M. unilineatus sp. nov. It appears to be related with M. trifidus Rafael & Marques, 2019 , described from Bolivia, as both species share the shape of tergite 8, distinct posterior inwardly setulose epandrial lobe, posterior cercus trifid, with each branch digitiform distally and hypandrium with a distal structure upwardly directed. It differs by the postcranium without dorsal pruinosity, sparsely gray pruinose on ventral half (versus entirely and sparsely gray pruinose in M. trifidus ); scutum with mid-longitudinal black stripe from pronotum to posterior margin of mesonotum (versus scutum without black stripe); one postsutural supra-alar seta (versus 2 postsutural supra-alar setae); hind tibia with distal tuft of around 15 longer dorsal setae (versus 5 longer dorsal setae along entire length); tergite 8 with elongate projection notched medially (versus tergite 8 without notable notch); epandrium with short posterior lobe inwardly directed (versus epandrium with elongate posterior lobe inwardly directed); hypandrium with distinct membranous area, apex with an elongate, less sclerotized spoon-shaped upwardly directed appendix (versus hypandrium without membranous area, apex hooked). Female specimens differ by sternite 8 without ventral keel; sternite 8 without mid-longitudinal, less sclerotized stripe and lateral perpendicular area distinct, desclerotized (versus sternite 8 with distinct ventral keel, distinct desclerotized mid-longitudinal stripe from base to the middle of sternite and without lateral perpendicular desclerotized area in M. trifidus ); genital fork wide with U-shaped mid-distal cleft (versus genital fork narrow); and genital chamber with two small sclerites (versus genital chamber without small sclerites).

Figures

FIGURE 13. Macrostomus unilineatus sp. nov., holotype ♂. A. Habitus, lateral view, before abdomen dissected; B. Head and thorax, dorsal view; C. Apex of abdomen, lateral view; D. Tergite 8, dorsal view; E. Tergite and sternite 8, lateral view; F. Sternite 8, ventral view; G. Epandrium, detached, lateral view; H. Epandrium posterior view; I. Cerci lobes, lateral view; J. Cercal bridge of anterior cercus, ventral projection of cercus and subepandrial sclerite, anterior view; K. Anterior anterior cercus and cercal bridge, anterolateral view; L. Cerci lobes, dorsal view; M. Posterior cercus, hypoproctal lobes and ventral process of cercus, posterior view; N. Hypandrium and ejaculatory apodeme, lateral view (white arrow indicating the membranous area); O. Hypandrium, posterior view (alveoli highlighted); P. Holotype and paratype labels. Scale bars, figure A = 2 mm; B = 1 mm; C, E–F, J = 0.3 mm; D, G–I, K–O= 0.2 mm. Abbreviations: a ce, anterior cercus; c brd, cercal bridge; d hyprct l, dorsal hypoproctal lobe; ej apod, ejaculatory apodeme; m ce, median cercus; mpac, mesial process of anterior cercus; p ce, posterior cercus; ph, phallus; subepand scl, subepandrial sclerite; st, sternite; t, tergite, v hyprct l, ventral hypoproctal lobe; vpc, ventral process of cerci.

FIGURE 14. Macrostomus unilineatus sp. nov., paratype ♀. A. Habitus, lateral view; B. Apex of abdomen, lateral view; C. Tergite 8, tergites 9+10 and cercus (inferior pieces), dorsal view, sternite 8, ventral view; D. Genital fork and genital chamber, ventral view. Scale bars, figures A = 2 mm; B = 0.3 mm; C–D = 0.2 mm.Abbreviations: gen ch, genital chamber; gen fk, genital fork.