Argolepida Metz & Irwin, 2003

Irwin, Michael E. & Winterton, Shaun L., 2021, Revision of South American stiletto fly genus Argolepida Metz & Irwin (Diptera: Therevidae: Therevinae), Zootaxa 5068 (2), pp. 151-185 : 152-154

Argolepida Metz & Irwin

Argolepida Metz & Irwin in Metz et al., 2003: 233 — Holston et al., 2007: 282 (figs 2–4) [phylogeny]; Gaimari & Webb, 2009: 643 [key]; Webb et al., 2013: 24 [catalogue]; Winterton et al., 2016: 151 (fig. 3) [phylogeny]; Irwin & Winterton, 2020b: 53 [key]. Type species: Psilocephala rivulosa Kröber, 1928: 21 , by original designation.

Common name. Silver-scaled stiletto flies

Diagnosis. Small, diminutive species; body extensively covered with white scale-like setae; male and female frons width approximately equal, wider than ocellar tubercle; antennae shorter than head; setal pile present medially on prosternum and on metanepisternum; cell m 3 closed; elongate leg macrosetae; abdomen relatively narrow along entire length.

Redescription. Head length and height subequal; frons flat (male) or slightly produced anterior to eye (female), pubescent, sometimes glabrous and glossy black medially; male and female frons width (at narrowest point) much wider than ocellar tubercle, not strongly sexually dimorphic; parafacial without setae; postocular macrosetae arranged in one row (dorsally) in both sexes, white scale-like (lanceolate) setae scattered medially on occiput; antenna shorter than head, scape short, less than 3x pedicel length, narrow; flagellum conical and approximately equal to combined scape and pedicel length. Thorax with central depression of prosternum and metanepisternum (postspiracular) setose; setae sometimes present on metakatepisternum; pleuron overlain with dense greyish-silver pubescence admixed with erect, white scale-like setae; scutum with adpressed, scale-like setae; scutal chaetotaxy (pairs of macrosetae): supra alar macrosetae, 1; post alar, 1; dorsocentral, 0; scutellar, 1; scutellum rounded in profile; leg macrosetae white, elongate and narrow; pulvilli very small, claws elongate; posterior surface of midcoxa with setae sometimes present; hind coxal knob present; femora with pale filiform setae admixed with adpressed scalelike setae; anteroventral macrosetae present on all femora, frequently as a series along segment, especially on hind femur; posteroventral macrosetae setae present only on hind femur, but row of finer setae on fore and midfemora; hind femur and tibia subequal in length to fore- and midfemora and tibiae; wing cell m 3 closed; vein R 1 with setae absent; wing vein R 2+3 slight sigmoid curve to wing margin; wing hyaline with dark venation, or white translucent with distinct mottled pattern, or darkened along wing veins, sometimes sexually dimorphic and darker in female. Male genitalia with dorsal apodeme of aedeagus broad, sub-quadrangular, covering aedeagus dorsally; distiphallus of aedeagus directed ventrally, short; lateral ejaculatory apodemes present; inner gonocoxal processes present, articulated, outer gonocoxal processes absent, hypandrium small, separate from gonocoxites; ventral lobe weakly sclerotised medially; female acanthophorite setae as two sets present (A1 & A2), A1 enlarged; sternite 8 posterior margin emarginate posteromedially; two spermathecae; spermathecal sac small and rounded; female tergite 8 elongate with broad posteromedial process.

Included species. Argolepida atacama sp. n., A. camposi sp. n., A. jama sp. n., A. oasis sp. n., A. patagonia sp. n., A. rivulosa (Kröber) , A. schlingeri sp. n. and A. telteca sp. n.

Comments. Argolepida is a small genus of diminutive flies with a body length rarely more than 7.5 mm. This is a very distinctive genus with a number of distinguishing features including the eyes of both sexes being widely separated, extensive pile of adpressed silver-white and black scale-like setae over the entire body, legs with elongate pale macrosetae and claws, and pulvilli small. There is limited sexual dimorphism in this genus with the frons only slightly narrower and vestiture only slightly more extensive in the male; the main sexually dimorphic feature is the presence and shape of the frontal glabrous patch ( Fig. 32 ), which is larger and frequently characteristically shaped in the female. Males and females are also similarly sized. All species of Argolepida are restricted to the Chacoan, Monte and Patagonian provinces. Argolepida is placed in the Cerocatus genus group and is closely related to Dasythereva and Elcaribe Webb, 2006 . Dasythereva and Argolepida share features such as the wide frons in both sexes and preponderance of scale-like setae over the body. The presence of setae on the metakatepisternum is rare in stiletto flies and is known only in Argolepida (some species) and Elcaribe .

Key to Argolepida species

1. Wing membrane completely or largely hyaline (e.g., Fig. 33A )................................................. 2.

- Wing membrane with large areas of infuscation (ranging from faint to distinct), especially along wing veins (e.g., Fig. 34A ).................................................................................................... 6.

2. Male frons uniform silver pubescent, or if glabrous area present, then minute and linear shaped ( Figs 32C, G ); abdominal tergites 1–7 with white, scale-like setae (both sexes) ( Figs 7 , 15 ).................................................. 3.

- Male frons silver pubescent with small medial glabrous area lacking pubescence ( Fig. 32E ); abdominal tergites 1–5 or 1–6 only with white, scale-like setae (both sexes) (e.g., Figs 5 , 11 )...................................................... 4.

3. Male femora dark, overlain with dense white-silver scale-like adpressed setal pile; female frons with large domed, black, glossy callus; katepisternum covered with erect, white, scale-like setae on anterior 2/3 ( Figs 6–9 ).............. A. camposi sp. n.

- Male femora yellow, overlain with sparse covering of white-silver, scale-like, adpressed setae; female frons with medium sized, black, glossy callus that is not distinctly domed; katepisternum covered with erect, white scale-like setae on anterior 1/3 ( Figs 14–16 ).................................................................................... A. oasis sp. n.

4. Abdominal tergites 1–6 with white, scale-like setae ( Figs 26 ).............................. A. schlingeri sp. n. (males).

- Abdominal tergites 1–5 only with white, scale-like setae ( Figs 3 , 13 )............................................ 5.

5. Frontal pubescence silver with substantial brownish suffusion in both sexes ( Figs 32E, F ).................. A. jama sp. n.

- Frontal pubescence uniform silver in male ( Fig. 32A ), female with brown suffusion dorsally only ( Fig. 32B ).................................................................................................... A. atacama sp. n.

6. Abdominal tergites 1–6 with white, scale-like setae (e.g., Figs 18 , 28 )........................................... 7.

- Abdominal tergites 1–5 with white, scale-like setae (e.g., Figs 22 , 31 )............................................ 8.

7. Female and male frons suffused with brown dorsally, female glabrous glossy area relatively small ( Fig. 32J )................................................................................................... A. patagonia sp. n.

- Female frons grey to silver, glabrous glossy area relatively large and occupying much of frontal area ( Fig. 32N )....................................................................................... A. schlingeri sp. n. (females).

8. Femora yellow ( Fig. 22 ); male and female frons with medium-sized glabrous glossy area (smaller in male), patch dorsally extended medially and at corners ( Fig. 32K, L ).............................................. A. rivulosa (Kröber) .

- Forefemur brown, mid- and hind femora yellow to brown ( Figs 28 , 29 ); female frons with large emarginate glabrous area, glossy black and slightly domed (see Fig. 32P ), male frons entirely silver pubescent, or if bare area present, then minute, and round or linear-shaped ( Fig. 32O )............................................................ A. telteca sp. n.

Figures

FIGURE 3. Argolepida atacama sp. n.: male, lateral view.

FIGURE 5. Argolepida atacama sp. n.: female, lateral view.

FIGURE 6. Argolepida camposi sp. n.: male, oblique view.

FIGURE 7. Argolepida camposi sp. n.: male, lateral view.

FIGURE 8. Argolepida camposi sp. n.: female, oblique view.

FIGURE 9. Argolepida camposi sp. n.: female, lateral view.

FIGURE 11. Argolepida jama sp. n.: male, lateral view.

FIGURE 13. Argolepida jama sp. n.: female, lateral view.

FIGURE 14. Argolepida oasis sp. n.: male, oblique view.

FIGURE 15. Argolepida oasis sp. n.: male, lateral view.

FIGURE 16. Argolepida oasis sp. n.: female, lateral view.

FIGURE 18. Argolepida patagonia sp. n.: male, lateral view.

FIGURE 22. Argolepida rivulosa (Kröber, 1928): male, lateral view.

FIGURE 26. Argolepida schlingeri sp. n.: male, lateral view.

FIGURE 28. Argolepida schlingeri sp. n.: female, lateral view.

FIGURE 29. Argolepida telteca sp. n.: male, oblique view.

FIGURE 31. Argolepida telteca sp. n.: female, lateral view.

FIGURE 32. Argolepida spp. heads, anterior view. A. Argolepida atacama sp. n., male; B. Argolepida atacama sp. n., female; C. A. camposi sp. n., male; D. A. camposi sp. n., female; E. A. jama sp. n., male; F. A. jama sp. n., female; G. A. oasis sp. n., male; H. A. oasis sp. n., female; I. A. patagonia sp. n., male; J. A. patagonia sp. n., female; K. A. rivulosa (Kröber, 1928), male; L. A. rivulosa (Kröber, 1928), female; M. A. schlingeri sp. n., male; N. A. schlingeri sp. n., female; O. A. telteca sp. n., male; P. A. telteca sp. n., female.

FIGURE 33. Argolepida spp. wings. A. Argolepida atacama sp. n.; B. A. camposi sp. n.; C. A. jama sp. n.; D. A. oasis sp. n.

FIGURE 34. Argolepida spp. wings. A. Argolepida patagonia sp. n.; B. A. rivulosa (Kröber, 1928); C. A. schlingeri sp. n.; D. A. telteca sp. n.