Nigranitida irwini Webb

Webb, Donald W. & Metz, Mark A., 2004, The South American genus Nigranitida Metz (Diptera: Therevidae: Therevinae) with the description of three new species, Zootaxa 757, pp. 1-16 : 10-12

Nigranitida irwini Webb spec. nov.

Etymology: This species is named after Dr. Michael E. Irwin, who was involved in the collection this species in Argentina.

Diagnosis. Like Nigranitida costata and N. gibba in lacking setae on the katepisternum. Like N. gibba in having the halter and maxillary palpus yellow and the posterior margin of the hypoproct ending distal to the apex of the cercus. It differs from N. gibba in having the male setae on the mesonotum dark brown intermixed with brownish gold setae; the gonostylus lacking a basodorsal lobe and lateral pointed flange; the anterior margin of the male ventral apodeme being deeply emarginate and lacking a pair of short, ventromedial projections; and the male ejaculatory apodeme extending beyond the anterior margin of the dorsal apodeme. The female frons is dark reddish brown, glossy with silver pruinescence ventrally and gray pruinescence along the lateral margin and on the ocellar tubercle.

Description of holotype male (MEI 106759).

Morphological variation (n = 2).

Body length 6.5 mm (6.5–6.7, 6.6 mm).

Head. Length 0.92 mm. Frons pruinescence silver gray ventrally becoming dark brown dorsally. Antenna dark brown, pruinescence gray, Ant./HL 0.85 (0.76–0.85, 0.80); scape length 0.20 mm, length/width 1.8 (1.7–1.8, 1.7), scape/pedicel length 2.0 (1.7–2.0, 1.8), scape/flagellum width 0.79 (0.75–0.79, 0.77), setae dark brown; pedicel length 0.10 mm (0.08–0.10, 0.09 mm), length/width 0.7; first flagellomere oval, tapered apically, flagellum length 0.48 mm (0.42–0.48, 0.45 mm), length/width 3.4 (2.6–3.4, 3.0), flagellum/ scape length 2.4 (2.1–2.4, 2.3). Parafacial pruinescence silver gray. Maxillary palpus yellow, brown basally; length 0.44 mm (0.38–0.44, 0.41 mm), length/width 5.5 (5.5–6.3, 5.9); setae yellow. Genal setae white. Occipital setae white ventrally becoming appressed, lanceolate dorsolaterally; macrosetae dark reddish brown, scattered.

Thorax. Macrosetae 3 np, 2 sa, 1 pa, 0 dc, 2 sc. Mesonotum dark brown, pruinescence gray; vittae dark brown separated by brownish gray pruinescent stripe; setae dark brown, erect intermixed with brownish gold, appressed, lanceolate setae. Pleuron dark brown, pruinescence white (occasionally glossy on anterodorsal third); setae white on propleuron, anepisternum, laterotergite, metanepisternum, and scutellum, absent on katepisternum. Wing. Length 5.5 mm (5.3–5.5, 5.4 mm), length/width 2.8 (2.8–2.9, 2.9); membrane opaque; veins pale brown; pterostigma dark brown. Halter pale yellow (dark brown on MEI 106756). Legs. Femora dark reddish brown, pruinescence white; ventral setae white; av 6:2:7 (6:2:5–7), pv 0:0:3 (0:0:1–3). Tibiae dark yellowish brown, dark brown apically. Tarsi dark brown.

Abdomen. Cuticle black, tergites 1–3 with posterolateral area dark yellow, pruinescence white across posterior margin of tergite 1, in broad posteromedial area on tergites 2– 5, over entire area of tergites 6–8; dorsal setae white, lanceolate, appressed; lateral setae white, erect. Terminalia . Epandrium ( Fig. 19 ) quadrate, anterior margin truncate, posterolateral margin tapering to thick point, setae dark yellow. Hypoproct ( Fig. 19 ), posterior margin slightly emarginate, ending distal to cercus. Gonocoxite ventral view ( Fig. 20 ) quadrate, lateral margin tapered posteriorly, median margin emarginate then tapering posteriorly to short, thick point, setae dark yellow with setae in mediolateral concavity directed ventrally; dorsal view ( Fig. 21 ) gonocoxal bridge large, pointed; lateral view ( Fig. 22 ) oval, tapering apically to broad point. Gonostylus ( Fig. 23 ) lacking basodorsal lobe; ventral margin rounded, setae dark yellowish brown. Aedeagus with dorsal apodeme ( Fig. 24 ) quadrate, tapered posteriorly; ventral apodeme ( Fig. 25 ), anterior margin deeply emarginate, tapered laterally to narrow point, ventral surface lacking pair of short, ventromedial projections; distiphallus ( Fig. 24 ) tapered posteriorly, lateral view ( Fig. 26 ), sinuate; ejaculatory apodeme ( Fig. 24 ) with posterior half bulbous, anterior half quadrate, anterior margin slightly emarginate, extending beyond anterior margin of dorsal apodeme.

Description of female.

Similar to male except for following.

Morphological variation (n=4).

Body length 6.8–7.2, 7.0 mm.

Head. Length 0.86–1.00, 0.94 mm. Frons dark reddish brown, glossy with silver pruinescence ventrally and grayish black pruinescence laterally and on ocellar tubercle; setae variable, dark reddish brown, short, in single row dorsally along margin on eye (MEI 106760), dark brown short, scattered on ventral fourth (MEI 121134), or absent (MEI 106761). Antenna varying from dark brown to dark yellowish brown; Ant./HL 0.69–0.85, 0.77; scape length 0.19–0.24, 0.22 mm, length/width 1.6–2.0, 1.9 mm, scape/pedicel length, 2.4–3.0, 2.8, scape/flagellum width 0.7–1.0, 0.8; pedicel length 0.08 mm, length/ width 0.7; flagellum length 0.42 mm, length/width 2.5–3.5, 2.9, flagellum/scape length 1.8–2.2, 1.9. Maxillary palpus length 0.34–0.42, 0.39 mm, length/width 4.8–7.0, 6.0. Occipital setae white ventrally becoming whitish pink, appressed, lanceolate dorsally.

Thorax. Macrosetae 3 np, 1–2 sa, 1 pa, 0 dc, 2 sc. Wing. Length 5.20–5.80, 5.50 mm, length/width 2.9–3.3, 3.0. Legs. Anteroventral macrosetae 3–5:1–3:3–10, pv 0:0:1–4.

Abdomen. Cuticle dark reddish brown, glossy, posterolateral corners of tergites 2–7 slightly orange­brown; dorsal setae dark reddish brown, appressed with white, elongate, appressed setae across posterior margin of tergites 1–4. Terminalia . Furca ( Fig. 27 ), length 0.38 mm, width 0.28 mm; spermathecal sac elongate, lobate, spermatheca spherical ( Fig. 27 ).

Biology. Nigranitida irwini has been hand netted on inland dunes and a white sand area, and in Malaise traps from 9 September to 22 March.

Specimens Examined. Type Specimen. The holotype male of Nigranitida irwini Webb (MEI 106759) was collected in ARGENTINA, Catamarca Prov., 28 km SE Tinogasta, 1,100 m, 17.X.1997, inland dunes, M.E. Irwin, F.D. Parker, S. Roig, 28.2450º S., 67.4557º W. and is deposited in the CAS (Type No. 18024). PARATYPES: ARGENTINA. CATA­ MARCA. San Fernando, Rio Belen, [­27.307, ­66.894], 1463 m, 17.X.1997, M. E. Irwin, F. D. Parker, S. Roig, 1 female MEI 106761 (CAS). LA RIOJA. General Lavalle, 10 km N Villa Union, [­29.222, ­68.246], 1234 m, 13–15.X.1997, M. E. Irwin, F. D. Parker, S. Roig, 1 male MEI 106758, 1 female 106760 (INHS), Malaise trap. MENDOZA. Lavalle, Parque Provincial Telteca, [­32.382, ­68.055], 9–17.IX.1999, M. E. Irwin, F. D. Parker, 1 female MEI 121134 (MEI), Malaise trap, dunes. TUCUMAN. Casa del Campo, km 992 along Highway 40, [­26.547, ­66.023], 1804 m, 18.X.1997, M. E. Irwin, F. D. Parker, S. Roig, 1 female MEI 106757 (MEI), white sand area.

Figures

FIGURES 19 – 27. Nigranitida irwini spec. nov. 19. Tergite 8, epandrium, cerci, hypoproct, dorsal view (MEI 106758). 20. Sternite 8, hypandrium, gonocoxite ventral view. 21. Gonocoxite, hypandrium, dorsal view. 22. Gonocoxite, left lateral view. 23. Gonostylus, left lateral view. 24. Aedeagus, dorsal view (inset ejaculatory apodeme cross­section). 25. Aedeagus, ventral view. 26. Aedeagus, left lateral view. 27. Female internal reproductive organs (MEI 106761). Scale = 0.1 mm.