Baccha, Mengual & Miranda & Thompson, 2018

Mengual, Ximo, Miranda, Gil Felipe G. & Thompson, F. Christian, 2018, Unraveling Ocyptamus and the Baccha legacy (Diptera: Syrphidae): redefinition of groups and new species descriptions, Zootaxa 4461 (1), pp. 1-44 : 4-7

Key to the New World groups of “ Baccha ” of authors

The identification key includes all the taxonomic groups from the New World that have been considered at some point as part of Baccha sensu lato by previous authors, or groups that comprise or have comprised species originally described as Baccha species, mostly due to the elongate and/or petiolate abdomen. The key is helpful to identify all the different genera and the significant species groups within them. Two species are keyed out due to their unique combination of morphological features: i.e., Ocyptamus pola ( Curran, 1939) and Ocyptamus maximus Thompson sp. nov., and a third species is keyed out because its genus is monotypic, Atylobaccha flukiella ( Curran, 1941) . Moreover, species left as incertae sedis appear in the identification key without any assigned genus name, i.e., grata Curran , conjunctus Wiedemann , sargoides Macquart , and placiva Williston. The only exception to this procedure with incertae sedis species is Ocyptamus maximus Thompson sp. nov., here placed under Ocyptamus but we acknowledge that its generic affinities are uncertain. Please refer to the below section ‘Nomenclatural acts arranged alphabetically by valid name’ for more information about these species.

1 Metafemur without spinose setae ( Fig. 1). Postmetacoxal bridge incomplete ( Fig. 11) or complete ( Figs 3, 4). Vein M1 at most slightly sinuate; vein R4+5 straight; rarely both veins strongly sinuate, but then without spinose setae on metafemur........ 3

- Metafemur with distinct anteroventral and posteroventral rows of spinose setae on apical 1/2 ( Fig. 2). Metepimera continuous behind metacoxae and forming a complete postmetacoxal bridge ( Figs 3, 4). Vein M1 very abruptly and strongly sinuate; vein R4+5 slightly to strongly sinuate ( Figs 5, 6).................................................................. 2

2 Vein R4+5 strongly sinuate ( Fig. 5). Abdominal tergum 1 produced laterally into a strong spur ( Figs 3, 9). Postmetacoxal bridge complete, wide ( Fig. 3). Dorsal occiput pile reduced to a single row............................ Salpingogaster Schiner

- Vein R4+5 only slightly sinuate ( Fig. 6). Abdominal tergum 1 with a small spur ( Fig. 10). Postmetacoxal bridge complete with a less sclerotized medial line (semi-membranous) ( Fig. 4). Dorsal occipital pile in 3–4 rows........... Eosalpingogaster Hull

3 Anterior anepisternum usually with some distinct short pile posterodorsally ( Figs 7, 8); metaepisternum usually with some long erect or subappressed pile ventrad to spiracle ( Fig. 11); always with pile on one of these two areas................. 5

- Anterior anepisternum ( Fig. 12) and metaepisternum bare...................................................... 4

4 Oral margin at the same level of facial tubercle, in lateral view ( Fig. 12); facial tubercle always present and in line with oral margin. Thorax without yellow markings except on scutellum..................................... Dioprosopa Hull

- Oral margin anterior to facial tubercle, in lateral view ( Fig. 13); if facial tubercle is missing, then face always pointed forward and oral margin beyond the medial point between oral margin and antennal bases ( Fig. 14). Postpronotum yellow; notopleuron usually yellow; pleuron more extensively yellow ( Fig. 13)....................................... Rhinoprosopa Hull

5 Male genitalia: phallus (aedeagus) simple, unsegmented. Face usually straight, oral margin and antennal bases in line, without tubercle ( Figs 15, 18). Abdomen petiolate; abdominal tergum 2 narrow, narrower than terga 3 and 4 ( Fig. 18). Female: abdominal segment 6 not noticeable nor visible without dissection, internal to segment 5.................... Leucopodella Hull [Note: Two undescribed species of Leucopodella have tuberculate face.]

- Male genitalia: phallus segmented into basiphallus and distiphallus ( Figs 58–60, 111). Face usually with a facial tubercle ( Figs 16, 32), at least slightly convex ( Figs 17). Abdomen variable. Female: abdominal segment 6 conspicuous, easily visible.... 6

6 Face gently convex; facial tubercle weak ( Fig. 17); metaepisternum bare; abdomen petiolate ( Fig. 19)............................................................................................... Atylobaccha flukiella (Curran)

- Face with distinct medial tubercle and/or more convex; metaepisternum bare or pilose; abdomen variable................ 7

7 Eye with a distinct triangular emargination on posterior margin ( Fig. 20). Ocellar triangle distanced from eye contiguity on male ( Fig. 21). Face convex or produced anteriorly ( Figs 20, 22). Abdomen usually oval or parallel-sided, never strongly petiolate or very long and narrow; abdominal markings usually constituted of apical dark fascia with a medial pair of dark vittae directed towards base in a yellow background ( Fig. 23) or a pattern derived from that ( Fig. 24), including entirely dark terga (Mengual 2011). Male genitalia with sclerotized, very short to long, triangular process arising from fused surstylar apodemes and projecting apically between bases of surstyli ( Figs 25, 26).................................. Toxomerus Macquart

- Posterior margin of eye with emargination usually indistinct or shallow and rounded ( Figs 27, 32). Ocellar triangle touching eye contiguity on male ( Figs 28, 57, 79). Face never produced anteriorly. Abdomen variable; abdominal markings never derived from medial pair of stripes as above ( Figs 29, 30). Male genitalia without such single acute sclerotized process, at most with a bilobate process ( Fig. 31).......................................................................... 8

8. Very large dark flies, larger than 20 mm. Abdomen petiolate, mostly dark; abdominal tergum 2 with two hyaline maculae basolaterally; sternum 2 translucent on basal 2/3 ( Figs 32, 33, 35, 37)... Ocyptamus maximus Thompson sp. nov. [incertae sedis]

- Flies never so large, less than 20 mm. Abdomen variable; if tergum 2 with hyaline maculae basolaterally, then fly pale and abdomen not petiolate ( Fig. 38).......................................................................... 9

9. Basoflagellomere deeply incised, forming dorsal and ventral lobes ( Fig. 40). Male tergum 4 concave apically, so apical abdominal segments can be flexed dorsally; male sternum 4 produced greatly ventrally ( Figs 40, 41, 42). Female abdominal segment 5 slightly asymmetric; female spermatheca large but abruptly narrowed on the end connected to the spermathecal duct, paddleshaped, covered in spine-like protuberances ( Fig. 43)................................... grata Curran [incertae sedis]

- Basoflagellomere oval to elongate ( Figs 27, 45). Male abdomen not so modified. Female abdominal segment 5 symmetric; female spermatheca not so modified...................................................................... 10

10. Antennal segments of similar length, subequal; antenna elongate ( Fig. 27). Abdominal terga 3 and 4 with a subbasal yellow fascia and a pair of oblique, pale vittae ( Fig. 44).............................. conjunctus Wiedemann [incertae sedis]

- Scape and pedicel each much shorter than basoflagellomere; antenna not elongate ( Figs 47, 54). Abdominal terga differently marked (except for placiva )............................................................................ 11

11. Abdomen parallel-sided, elongate, mainly orange and without a distinct pattern of markings ( Fig. 38); tergum 2 with basolateral hyaline areas. Metafemur pale with long, thick, mostly orange pile on dorsal and ventral surface ( Fig. 39), with a few long black pile basoventrally..................................................... sargoides Macquart [incertae sedis]

- Abdomen variable; abdominal segment 2 without hyaline areas. If metafemur pale with long, thick pile, then pile black ( Fig. 103) and abdominal terga with four pale vittae............................................................. 12

12. Wing almost completely bare, microtrichose on apical 1/4 ( Fig. 46)........................... Pseudoscaeva Vockeroth

- Wing extensively microtrichose......................................................................... 13

13. Pedicel with narrow projection over basoflagellomere ( Fig. 45); basoflagellomere sub-triangular, usually large on female. Scutum with a distinct anterior row of longer pile, i.e. mesonotal collar ( Fig. 49). Abdomen parallel-sided to slightly oval............................................................................. Ocyptamus Macquart sensu stricto

- Apical margin of pedicel straight, rounded, without an extension over basoflagellomere ( Fig. 51); basoflagellomere oval to round. Scutum usually without an anterior row of longer pile. Abdomen variable................................. 14

14. Eye sometimes pilose ( Figs 52, 54). Abdomen spatulate, never Syrphus -like ( Fig. 53). Wing mostly dark with hyaline areas on basomedial cells ( Figs 52, 53).................................................................... Styxia Hull

- Eye usually bare; if eye pilose, then abdominal pattern Syrphus -like ( Fig. 55). Wing never as above................... 15

15. Metasternum pilose. Face broad, broader than a 1/3 of the head’s width ( Fig. 57). Flies with oval, parallel-sided or slightly petiolate abdomens ( Figs 55, 56); some species with an abdominal pattern similar to the abdominal pattern of genus Syrphus ( Fig. 55). Male phallus with long spines apically ( Fig. 58d) or postgonite bifurcate ( Fig. 60c) or postgonite tooth-like ( Fig. 58c, 5 9c)............................................................................... Orphnabaccha Hull , in part [Note: There are species with very few pile and it is not uncommon for them to eventually fall, making the metasternum look bare (e.g. species from the O. coerulea species group).]

- Metasternum never pilose. Face narrower, usually around a 1/3 or less of head’s width. Abdomen variable, never similar to Syrphus . Male genitalia never with long spines on phallus, never with a bifurcate or tooth-like postgonite............... 16

16. Abdominal terga 3 and 4 with yellow ‘L’ shaped markings ( Fig. 30). Male genitalia usually enlarged.............................................................................................. Ocyptamus callidus species group

- Abdominal terga never as above. Male genitalia variable..................................................... 17

17. Metaepisternum bare. Abdomen parallel-sided to slightly constricted, with inverted V-shaped yellow fascia on terga 3 and 4, sometimes interrupted medially ( Fig. 61)................................................. Pipunculosyrphus Hull

- Metaepisternum usually pilose ( Fig. 11); if metaepisternum bare, then abdomen differently marked................... 18

18. Vein M1 sinuous ( Figs 71, 72, 73); other characters not found in the combination below............................. 20

- Vein M1 straight, joining vein R4+5 perpendicularly ( Figs 62, 65); wing either hyaline with an apical brown macula, or uniformly yellowish to brown. Small flies usually with short abdomen, shorter than wings............................. 19

19. Scutum shining black with three narrow white pollinose vittae, medial vitta longer ( Fig. 63). Wing hyaline with apical dark macula, extensively bare ( Fig. 62). Scutellum partially black. Abdominal terga 3 and 4, at least, black with five narrow pale vittae ( Fig. 63)........................................................................ Calostigma Shannon

- Scutum usually dull ( Fig. 67); if shining black, then without distinct pattern ( Fig. 64). Wing never as above, usually brownish yellow, extensively microtrichose ( Fig. 65). Abdominal terga mostly pale with three apical dark vittae ( Fig. 66) or dark with at most four pale vittae ( Figs 67, 68, 69), never with five pale vittae................ Ocyptamus lepidus species group, in part

20. Vein R4+5 almost straight; vein M1 not strongly sigmoid ( Figs 73, 94). Male genitalia never with enlarged nor elongate cercus. Other characters not found in the combination below........................................................ 22

- Vein R4+5 and M1 distinctly sinuous ( Figs 71, 72): vein R4+5 with shallow dip into cell r4+5, and vein M1 strongly sigmoid. Frontoantennal area protruded, prominent ( Fig. 75). Abdomen strongly petiolate ( Figs 71, 72). Male genitalia enlarged ( Fig. 74)..................................................................................................... 21

21. Metacoxa and metatrochanter with tuft of thick pile ( Fig. 74). Male genitalia with cercus greatly enlarged ( Fig. 76). Basoflagellomere elongate, much longer than broad, acute apically ( Figs 72, 74). Large flies, greater than 12 mm ... Mimocalla Hull

- Metacoxa and metatrochanter without tuft of thick pile ( Fig. 75). Male genitalia with normal-sized cercus ( Fig. 77). Basoflagellomere oval, about as long as broad ( Figs 71, 75). Medium-sized flies, about 11 mm .... placiva Williston [incertae sedis]

22. Ocellar triangle never contrasted as below, either entirely pale pollinose ( Fig. 79) or with sparse pollinosity ( Fig. 80). Dorsal occiput pilosity variable............................................................................... 24

- Ocellar triangle dull black pollinose, surrounded by dense pale pollinosity ( Fig. 78). Dorsal occiput with a single row of pile ( Fig. 78) ( Hybobathus )................................................................................ 23

23. Scutum covered by dense pale pollinosity, with sub-shining vittae ( Figs 73, 81). Medium-sized flies (7–10 mm)................................................................................... Hybobathus Enderlein sensu stricto

- Scutum black with three golden pollinose vittae that merge posteriorly into a pollinose area anterior to scutellum ( Fig. 82). Larger flies (11–18 mm)........................................................ Hybobathus arx species group

24. Abdomen long, almost as long as wing, parallel-sided with subbasal yellow fascia on terga 3–5 ( Fig. 83). Alula narrow and linear (almost uniform width throughout), approximate length:width ratio = 5:1 (see Vockeroth 1969: Fig. 13); wing infuscate ( Fig. 83).......................................................... Hermesomyia wulpiana (Lynch Arribálzaga)

- Abdomen variable, never with the above character combination. Alula variable................................... 25

25. Orange flies with narrow abdomen ( Fig. 85). Male with a pair of long apicolateral extensions on sternum 4............................................................................. Ocyptamus melanorrhinus species group, in part

- If the abdomen is narrow, then the overall body color is dark brown to black ( Figs 86, 87), never orange. Male without such extensions on sternum 4............................................................................... 26

26. Abdomen usually petiolate, with narrow base and abruptly widening ( Fig. 89) or very narrow and very long, delicate (2nd abdominal segment ≥ 8 times longer than wide; Fig. 84); if abdomen parallel-sided, narrow and elongated, then tergum 3 never with a pair of subbasal quadrangular / triangular maculae..................................................... 28

- Abdomen parallel-sided, narrow but not delicate (2nd abdominal segment ≤ 6 times longer than wide) and elongated ( Figs 87, 88), slightly expanding apically; tergum 3 with subbasal pair of quadrangular / triangular maculae that sometimes form a complete fascia.......................................................................................... 27

27. Wing hyaline with a central, triangular dark vitta; alula present ( Figs 86, 88)......... Ocyptamus fascipennis species group

- Wing either entirely hyaline or light brown; alula absent ( Fig. 87)......... Ocyptamus melanorrhinus species group, in part

28. Scutum yellow laterally ( Fig. 64); scutellum usually yellow, rarely mostly dark. Wing usually light yellow. Abdomen either spatulate, parallel-sided or petiolate ( Figs 67, 68, 69 respectively), never narrow and delicate. Male genitalia: subepandrial sclerite extended beyond base of surstyli as pair of lobes ( Fig. 31); if subepandrial sclerite not extended beyond base of surstyli, then M1 joining R4+5 at right angle ( Fig. 65).................................. Ocyptamus lepidus species group

- Scutum and scutellum usually entirely black ( Fig. 90); if scutum yellow laterally or scutellum mostly yellow, then either scutum with a distinct pattern of golden pollinose vittae on a black background and abdominal terga with a central pair of pale oval-shaped vittae ( Fig. 91), or abdomen very narrow and delicate (2nd abdominal segment ≥ 8 times longer than wide; Figs 70, 84). Wings hyaline or mostly dark brown. Abdomen either petiolate ( Fig. 91) or very narrow, long and delicate ( Figs 70, 84). Male genitalia: subepandrial sclerite never extended beyond base of surstyli as pair of lobes and vein M1 never straight.... 29 29. Abdomen very narrow and delicate through all its extent (2nd abdominal segment ≥ 8 times longer than wide; Figs 70, 84). Frons or frontal triangle usually rugose ( Figs 70, 92). Alula absent ( Fig. 94). Male surstylus quadrangular and either with extended apex or apical filiform projection ( Fig. 95); female tergum 7 without apodemes ( Fig. 97)............................................................................................ Ocyptamus stenogaster species group

- Abdomen usually petiolate ( Fig. 91). If alula absent, abdomen very narrow and delicate, and frons and frontal triangle rugose, then face mostly dark ( Fig. 93), male surstylus subtriangular without projection ( Fig. 96), and female tergum 7 with long basolateral apodemes ( Fig. 98).............................................................................. 30

30. Scutum usually pale laterally, with three golden pollinose vittae on a black background: middle vitta usually complete and narrow, others tapered and incomplete, not reaching the scutellum ( Figs 91, 99). Female segment 6 usually with weak fusion line at least on basal 1/2 ( Fig. 101)................................................. Pelecinobaccha Shannon , in part [Note: The P. summa species group keys out here.]

- Scutum without distinct patterns of pollinosity and entirely dark ( Figs 89, 100). Female segment 6 divided into tergum and sternum or as a single conical sclerite ( Fig. 102)............................................................ 31

31. Metabasitarsomere with at least basal 1/2 dark or mostly dark ( Fig. 103)......................................... 33

- Metabasitarsomere wholly pale or mostly pale ( Fig. 104)..................................................... 32

32. Pro and mesolegs mostly dark ( Figs 104, 105). Abdomen dark with flat, scale-like, shinning pile ( Figs 56, 105).......................................................................................... Orphnabaccha Hull , in part [Note: Orphnabaccha species, mostly from the O. coerulea species group, may key out here if the male genitalia characters are not checked or the metasternum pilosity is overlooked or looks bare.]

- Pro and mesolegs mostly pale. Abdomen with yellow vittae and dark pile ( Fig. 112)............................................................................................. Ocyptamus pola (Curran) [ O. lepidus species group] [Note: Ocyptamus pola belongs to the O. lepidus species group, but its particular morphology may create confusion with Pelecinobaccha or Relictanum . It is keyed out here to avoid misidentification.]

33. Dorsal occiput with two or more rows of pile, anterior row sometimes short but still distinct ( Figs 7, 106). Female segment 6 usually modified into a single conical sclerite with no distinction between tergum and sternum ( Fig. 102)........................................................................................... Pelecinobaccha Shannon , in part

- Dorsal occiput with a single row of pile ( Fig. 107). Female 6th segment divided into tergum and sternum...................................................................................................... Relictanum Miranda