Gimnomera Rondani

Chagnon, Marie-Eve & Sinclair, Bradley J., 2020, Revision of the Nearctic species of Gimnomera Rondani (Diptera: Scathophagidae) with morphological phylogeny and DNA barcodes, Zootaxa 4853 (3), pp. 369-403 : 372-373

Gimnomera Rondani

Gimnomera Rondani, 1866: 4 , 21. Type-species, Cordylura tarsea Fallén (original designation). Other type species designation:

Cordylura dorsata Zetterstedt ( Becker, 1894: 182, proposed type designation). See “Notes on synonymy”.

Gymnomera ( Rondani, 1866: 51; Hendel, 1930: 79; Ozerov, 1999a: 121; Šifner, 2003: 32–36) (See O’Hara et al. 2011).

Cochliarium Becker, 1894: 183 . Type-species, Cordylura cuneiventris Zetterstedt, 1846 (original designation).

Dasypleuron Malloch, 1919: 79 . Type-species, Dasypleuron tibialis Malloch, 1919 (original designation).

Paragymnomera Hendel, 1930: 80 . Type-species, Cordylura dorsata Zetterstedt, 1838 (original designation).

Rhopochilus Enderlein, 1936: 136 . Type-species, Cochliarium lasiostoma Becker, 1894 (original designation).

Langechristia Ozerov, 1999b: 510 . Type-species, Langechristia ziegleri Ozerov, 1999b (original designation) ( Ozerov 2019:

197, new synonym).

Notes on synonymy. Becker (1894: 182) listed Cordylura dorsata Zetterstedt as type species for Gimnomera even though Cordylura tarsea Fallén was already listed by original designation by Rondani (1866: 21). See O’Hara et al. (2011) for further information.

Šifner (2008: 132) also included Opsiomyia Coquillett, 1898 as a synonym of Gimnomera , citing Vockeroth (1965: 836). But this is a mistake, as on the listed page in Vockeroth’s catalogue, the genus is shown as a new synonym of Trichopalpus Rondani, 1856 .

The type species for Paragymnomera Hendel has widely been cited as Gimnomera hirta (e.g., Šifner 2008: 132). However, Hendel (1930) clearly stated in the description of Paragymnomera that the type species is Gimnomera dorsata (Zetterstedt) . In fact, Šifner (2003: 32) listed G. dorsata as the type species.

Diagnosis. Gimnomera can be distinguished from other Scathophagidae genera by the presence of a cluster of short setae on the outer margin of the postpronotum; strong apical and lateral scutellar setae; single katepisternal seta; apical half of vein R 1 usually with a row of setulae.

Description. Male. Body length 3.75–4.16 mm. Small-bodied flies variable in colour, ranging from yellow to black, either matte or shiny. Overall species weakly bristled. Head rounded with inconsistent number of vibrissae; arista micropubescent to bare, palpus slender, teardrop-shaped. Thorax with postpronotum always with cluster of short setae on outer margin, appearance can be short, stout, erect black spine-like or lightly coloured, fine soft setulae; similar setae present along anterior margin of postpronotum and scutum. Scutal setae variable in appearance and number, notopleurals, supra-alars, postalars and dorsocentrals distinct. Acrostichal setae in two rows. Scutum with fine setulae among setae. Scutellum always with strong apical and lateral setae; proepisternum with setulae; 1 katepisternal seta. Wing: dorsal surface of R 1 always (at least for Nearctic species) with row of setulae on apical half; setulae variable in number. Legs: short setae present, with no discernible pattern. Abdomen: weakly bristled with soft setulae. Sternite 5 ( Figs 29, 30 ) with two, usually short, projections with margins spinulose. Male terminalia: surstylus ( Figs 1–16 ) large, curved slightly, usually enlarged apically. Cercus ( Figs 1–16 ) large, bifid, truncate or pointed apically. Pregonite variable, broad, slender or branched; apical end usually with heavy black setae. Female. Body length 3.95–4.16 mm. Differs from male as follows: Female postabdomen ( Figs 23, 24 ): segments 5–8 laterally flattened; tergite 7 expanded ventrally, enclosing narrow sternite 7; sternite 7 divided medially; tergite and sternite 8 usually fused, completely divided medially, prolonged apically; membrane between tergites and sternites 7 and 8 with pale to dark spines (absent in G. vockerothi , Fig. 25 ); proctiger shifted dorsally between sclerites of segment 8 (apical in G. vockerothi ) (see Ovchinnikov 2009, figs 19–21); 3 spermathecae present.

Remarks. After examination of the type specimens of G. fasciventris Malloch , it was concluded that this species is not congeneric with Gimnomera and keyed out in Vockeroth (1987) to Acerocnema Becker, 1894 . This species is characterized by an elongate postpedicel, about five times as long as the pedicel, R 1 with row of only four setulae, and very different male terminalia compared to Gimnomera . Based on this evidence, Gimnomera fasciventris is transferred to the genus Acerocnema , comb. nov.

Engelmark & Haarto (2019) proposed a new subgenus, Ozerovia , for the single species, G. albipila ( Zetterstedt, 1846) . They recognized this subgenus based on differences in the head and scutal chaetotaxy. An assessment of subgeneric subdivision of Gimnomera was not possible in this study.

Key to Nearctic species of Gimnomera

1 Yellowish to brown species, pleura yellow to light brown, often the whole body yellow ( Figs 18, 20 ).................. 2

- Blackish species, pleura brown or black ( Figs 17, 19 )........................................................ 7

2 At least 4 weak to strong dorsocentrals present, at least setulae forming distinct row................................ 3

- Only postsutural pair of dorsocentrals present (prescutellar pair), not forming distinct rows......................................................................................... Gimnomera cuneiventris (Zetterstedt) [in part]

3 Scutellum yellow in contrast to brown scutum................................................ Gimnomera sp. A

- Scutellum concolourous with scutum..................................................................... 4

4 Anterior margin of scutum and postpronotum with dark setae, sometimes spine-like ( Fig. 26 ) … Gimnomera cerea (Coquillett)

- Anterior margin of scutum and postpronotum with light coloured setulae, fine and not spine-like ( Fig. 27 ).............. 5

5 One postpronotal seta; postcranium brown and postgena yellow ( Fig. 21 ); scutum shiny with distinct rows of pale acrostichal and dorsocentral setulae/ setae........................................... Gimnomera vockerothi sp. nov. [in part]

- Two postpronotal setae; postcranium same colour as postgena; scutum pruinescent with dark setae ( Fig. 27 )............. 6

6 Pedicel dark, similar to postpedicel; male rectangular in shape, with small lobe protruding laterally ( Fig. 11 )..................................................................................... Gimnomera terrywheeleri sp. nov.

- Pedicel yellow, postpedicel dark; male cercus triangular with no protrusions ( Fig. 7 ) Gimnomera incisurata Malloch [in part]

7 Antenna with postpedicel, pedicel and scape yellow ( Fig. 17 )........................ Gimnomera subvittata (Malloch)

- Antenna with postpedicel black, pedicel and scape black to yellow ( Fig. 19 )...................................... 8

8 Thorax with more than 4 pairs of dorsocentral setae, usually 2–3 presutural pairs and 2–4 postsutural pairs; if only 1 pair (prescutellar pair), dorsocentral and acrostichal setulae in distinct rows............................................. 9

- Thorax with 1 postsutural dorsocentral seta (prescutellar pair), without distinct rows of dorsocentral and acrostichal setulae............................................................... Gimnomera cuneiventris (Zetterstedt) [in part]

9 Postpronotal lobe with 1 seta........................................................................... 10

- Postpronotal lobe with 2 setae.......................................................................... 12

10 Major setae on scutum and scutellum pale; surstylus expanded apically in lateral view; female terminalia not highly sclerotized and segment 8 not prolonged posteriorly ( Fig. 25 )........................... Gimnomera vockerothi sp. nov. [in part]

- Major setae on scutum and scutellum black; if pale, surstylus not expanded apically in lateral view and female terminalia heav- ily sclerotized and segment 8 prolonged posteriorly ( Figs. 23, 24 ).............................................. 11

11 Male cerci rectangular, expanded laterally ( Fig. 1 ); female terminalia with tergite and sternite 8 not fused, both projecting posteriorly; intersegmental membrane between 7 and 8 clothed with short pale spines ( Fig. 23 ). Gimnomera aquilonia sp. nov.

- Male cerci triangular, tapered to narrow apex ( Fig. 13 ); female terminalia with tergite and sternite 8 fused, strongly projecting posterodorsally; intersegmental membrane between 7 and 8 clothed with long dark spines ( Fig. 24 )......................................................................................... Gimnomera tibialis (Malloch) [in part]

12 Scutum with pale golden setae.......................................... Gimnomera incisurata Malloch [in part]

- Scutum with black setae................................................ Gimnomera tibialis (Malloch) [in part]

Figures

FIGURES 26–30. Morphological features of Gimnomera. 26–27. View of anterior margin of postpronotum with dark spine-like setae or with light coloured setulae: 26. G. cerea (Coquillett); 27. G. terrywheeleri sp. nov.; 28. G. tibialis (Malloch), vein R1 with row of setulae; 29–30. Male sternite 5: 29. G. subvittata (Malloch); 30. G. vockerothi sp. nov..

FIGURES 1–4. Gimnomera male terminalia, posterior and lateral views. 1–2. G. aquilonia sp. nov.; 3–4. G. cerea (Coquillett). Abbreviations: cerc—cercus; epand—epandrium; hypd—hypandrium; pregt—pregonite; sur—surstylus.

FIGURES 5–8. Gimnomera male terminalia, posterior and oblique lateral views. 5–6. G. cuneiventris (Zetterstedt); 7–8. G. incisurata Malloch. Abbreviations: cerc—cercus; epand—epandrium; pregt—pregonite; sur—surstylus.

FIGURES 9–12. Gimnomera male terminalia, posterior and lateral views. 9–10. G. subvittata (Malloch); 11–12. G. terrywheeleri sp. nov. Abbreviations: cerc—cercus; epand—epandrium; hypd—hypandrium; pregt—pregonite; sur—surstylus.

FIGURES 13–16. Gimnomera male terminalia, posterior and lateral views. 13–14. G. tibialis (Malloch); 15–16. G. vockerothi sp. nov. Abbreviations: ph—phallus; pregt—pregonite.

FIGURES 23–25. Female abdomen of Gimnomera species. 23. G. aquilonia sp. nov.; 24. G. tibialis (Malloch); 25. G. vockerothi sp. nov. Abbreviations: hyprt—hypoproct; spmth—spermathecae; st—sternite.

FIGURES 17–20. Male and female Gimnomera, lateral views. 17. G. subvittata (Malloch), male; 18. Female of possible ninth species of Nearctic Gimnomera (Gimnomera sp. A); 19. G. tibialis (Malloch), female; 20. G. vockerothi sp. nov., female.

FIGURES 21–22. Gimnomera vockerothi sp. nov., female. 21. Colour patterns on the occiput; 22. Colour pattern on scutellum.