Melanostomini
Creators: name: Montoya, Augusto L.
name: Wolff, Marta
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Syrphidae

description: Identification key to the Neotropical genera of Melanostomini and Bacchini
A key to the genera of Neotropical Melanostomini and Bacchini was prepared based on characters proposed by Fluke (1945, 1957), Thompson (1999a), Thompson (2006), Thompson et al. (2010), Huo (2014), Thompson & Skevington (2014), Young et al. (2016), Miranda & Moran (2017), Ramage et al. (2018) and Mengual (2020).
1. Postpronotum pilose (MCAD Fig. 30); male abdomen with four unmodified pregenital segments; 5 th tergum usually not visible in dorsal view (MCAD Figs 1, 4); female abdomen tergum 6 th hardened or membranous, visible, if tergum 6 th and onward visible, then these are membranous; epiproct as two plates that may be connected to the base, or as a single plate, or as a band with two projections (subfamilies Eristalinae, Microdontinae and Pipizinae).... other flower flies (“MCAD key couplet 2”)
- Postpronotum bare; male abdomen with five unmodified pregenital segments; 5 th tergum visible in dorsal view (MCAD Figs 53–61); female abdomen tergum 6 th hardened, visible; epiproct divided into two plates that may be connected to the base (subfamily Syrphinae)................................................................................. 2
2. Face and/or scutellum partially yellow or yellowish-brown in background color; phallus (aedeagus) two-segmented........................................................................................ other Syrphinae genera
- Face and scutellum entirely black in background color (some species with partly pale face or scutellum); phallus (aedeagus) simple, unsegmented (Bacchini and Melanostomini)......................................................... 3
3. Face usually straight, oral margin and antennal bases in line, without tubercle, flat, straight or convex; abdomen petiolate, distinctly narrower than thorax (Fig. 4A, MCAD Figs 59, 60); male: 2 nd tergum narrow, narrower than 3 rd and 4th terga (Mengual et al. 2018, Fig. 18); female abdominal tergum 6 th, not noticeable nor visible without dissection, tergum 6 th internal to the 5 th, tergum 5 th 1/10 of the length of tergum 4 th, almost inconspicuous (Miranda & Moran 2017, Figs 59, 80 and 90)................................................................................................ Leucopodella Hull
- Face with tubercle; abdomen parallel-sided or narrowly oval (MCAD Figs 55, 58); other characters variable; female tergum seventh visible without dissection........................................................................ 4
4. Antennal cavities broadly confluent (MCAD Fig. 24); face narrow, with distinctive, rounded facial tubercle; metathoracic pleuron with several fine subappressed pile ventral to spiracle; katepisternum with pile patches broadly separated posteriorly, but joined anteriorly; abdomen oval, wide and flat, clearly broader than scutum, usually with yellow-orange maculae on 2 nd to 4 th terga; surstyli elongated, one-lobed, digitiform or pointed, generally widened apically, postgonites small, squarish or triangular in shape (Fluke 1957: 278, Figs 119–122; Borges & Pamplona 2003); female tergum 5 th 1/3 of the length of tergum 4 th, tergum 6 th 1/3 of the length of 5 th (Miranda & Moran 2017, Figs 66, 84 and 97)................. Xanthandrus Verrall
- Antennal cavities broadly separated (MCAD Fig. 23); metathoracic pleuron bare; katepisternum with pile patches usually broadly separated throughout; abdomen variable, slender and parallel-sided, as broad as scutum; other characters variable... ................................................................................................... 5
5. Metasternum greatly reduced to a small diamond-shaped area (Figs 3A, 5J; Andersson 1970: 273, Fig. 1C, 3C; Shatalkin 1975: 118, Fig. 11; Thompson et al 2010: 771, Fig. 34; Haarto and Ståhls 2014: 95, Figs 1A; Thompson & Skevington 2014); antenna short, with scape and basoflagellomere as long as wide; face not produced below, with small tubercle, facial pollinosity neither punctate nor rippled (MCAD Fig. 28); male abdomen nearly parallel-sided, from two to five times as long as greatest width, female with abdomen varying from nearly parallel-sided to oval, from 1.7 to 2.5 times as long as greatest width; usually with triangular or subquadrate shaped yellow maculae; male genitalia with surstyli simple, one-lobed, elongate, straight and thin, with a small basomedial tubercle; postgonites (apex of hypandrium) massive, irregular or squarish in shape; female tergum 5 th 1/4 of the length of tergum 4 th, tergum 6 th 1/5 of the length of tergum 5 th ......................... Melanostoma Schiner [Note: A new species described from Cameroon by Mengual (2020) does not have the reduced metasternum]
- Metasternum entire, not reduced (Fig. 3B; MCAD Fig. 35; Haarto and Ståhls 2014: 95, Fig. 1B; SNLSA Fig. 12C); face variable, almost straight in profile with weak tubercle or moderately to strongly produced forward ventrally, sometimes with pollinosity forming punctuate or rippled pattern, other characters variable........................................ 6
6. Face produced forward into a snout, with a very prominent and abrupt tubercle closer to the antennal base than to the oral opening apex (Fig. 4N, Fluke 1943: 427, Figs 1–7); face sparsely pollinose and without punctate shiny (bare) maculae (Fig. 4N); head as long as or longer than high, wider than thorax; male eyes dichoptic or holoptic; antenna elongate, as long as or longer than face; basoflagellomere elongate, four or more times as long as broad, near equal to scape and pedicel together (Fig. 4N); notopleura without a distinct tubercle; subscutellar fringe short, thin and white; prolegs simple in male, sometimes with a curled tibial seta (Fig. 4N, Fluke 1943: 427, Figs 8–9); male genitalia with surstyli curved; superior lobes transverse and elongated; ejaculatory apodeme elongate and knobbed toward the apex (Fluke, 1957: 278, Figs 124–125; Shatalkin 1975: 118, Fig. 12); small species, shining black or blue metallic, 7mm or less.............. Platycheirus (Tuberculanostoma) Fluke
- Face straight or slightly produced anteriorly, with a low and indistinct tubercle, frequently densely pollinose and with small shiny punctate-like bare maculae; head higher than long; male eyes face not greatly produced anteriorly; basoflagellomere oval or slightly elongate, never more than twice as long as broad; notopleura with a distinct tubercle; subscutellar fringe complete; male sometimes with legs modified, either broadened or with special bristles, pile tufts, modified hairs or none; frequently medium to large flies, sometimes with pale to metallic colored markings......................................... 7
7. Face slightly receding to rather strongly produced below, with obscure to prominent tubercle, densely pollinose and sometimes with pollinosity forming a distinctive bare punctum or rippled pattern (Fig. 4M); male protibia usually with long black bristles posteriorly, sometimes protibia and/or tarsus expanded, usually with specialized setae (Fig. 4M); abdomen nearly parallel-sided in males, narrowly oval in the female; with yellow to orange or silver-gray pollinose on bluish submetallic macula, generally with quadrate markings; surstyli bifid or bilobed with a long, slightly curved lateral lobe and a short, stout basomedial lobe, superior lobes usually slender, recurved and crescent-shaped (Vockeroth 1990: Fig. 83; Thompson & Skevington 2014; Young et al. 2016); female tergum 5 th 1/3 of the length of tergum 4 th, tergum 6 th 1/5 of the length of tergum 5 th (Miranda & Moran 2017, Figs 70, 71, 86 and 100).......................................................... Platycheirus (Carposcalis)
- Face straight in profile, not produced anteriorly, usually uniformly pollinose, sometimes with shiny (bare) punctate maculae; male legs slender, without bristles, pile tufts, or modified hairs; abdomen frequently with pale-colored maculae; surstyli elongate, one-lobed, postgonites massive, irregular, elongate, triangular, or squarish in shape......................... 8
8. Antennae short, scape broader than long, scape nearly equal to pedicel, basoflagellomere large, slightly oval and apically rounded; face slightly receding to perpendicular with a well-rounded tubercle, never with transverse grooves dorsally along tubercle neither broadly (bare) punctuate (Fig. 6D); mesocoxa pilose posteriorly (Fig. 6E, SNLSA Figs 12–13); abdomen elongated or with parallel sides, with four to five pairs of large rounded to triangular markings on terga, always with small macula on 5 th tergum; male genitalia greatly enlarged and strongly sclerotized, apex of hypandrium (superior lobes) and cerci elongated, surstyli three to four times longer than wide (Fig. 6G, Fluke 1957: 278, Fig. 123; SNLSA Figs 14A–D); female tergum 5 th 1/4 of the length of tergum 4 th, tergum 6 th 1/5 of the length of tergum 5 th (SNLSA Figs 13E)...... Talahua Fluke [Note: Montoya & Wolff (2020) provided a complete redescription for Talahua, differential diagnosis, images of the habitus and illustrations of male genitalia]
- Antenna elongate, scape longer than broad; basoflagellomere oval or elongate; face straight in profile (Figs 4, 6 – 9, MCAD Fig. 22), facial tubercle low dorsally, not distinct (Figs 4, 6 – 9); mesocoxa bare posteriorly; male genitalia normal size, apex of hypandrium (superior lobes) triangular to rectangular, irregular in shape and cercus short; female tergum 5 th 1/3 of the length of tergum 4 th, tergum 6 th 1/4 of the length of tergum 5 th (Figs 5, 6 and 9)................. Argentinomyia Lynch-Arribálzaga
description: Published as part of Montoya, Augusto L. & Wolff, Marta, 2023, Taxonomic revision of the Neotropical genus Argentinomyia Lynch-Arribálzaga, 1891 (Diptera: Syrphidae), with description of 16 new species, pp. 1-157 in Zootaxa 5234 (1) on pages 12-13, DOI: 10.11646/zootaxa.5234.1.1, http://zenodo.org/record/7609993