Revision of the Nearctic Species of the Shore-Fly Genus Scatophila Becker (Diptera: Ephydridae) Author Zatwarnicki, Tadeusz 0000-0003-2163-0143 Institute of Biology, Opole University, ul. Oleska 22, 45 - 052 Opole, Poland zatwar @ uni. opole. pl; https: // orcid. org / 0000 - 0003 - 2163 - 0143 zatwar@uni.opole.pl Author Mathis, Wayne N. 0000-0003-2163-0143 Institute of Biology, Opole University, ul. Oleska 22, 45 - 052 Opole, Poland zatwar @ uni. opole. pl; https: // orcid. org / 0000 - 0003 - 2163 - 0143 & Department of Entomology, PO BOX 37012, MRC 169, Smithsonian Institution, Washington, DC 20013 - 7012, USA mathisw @ si. edu; https: // orcid. org / 0000 - 0002 - 5012 - 1762 & Institute of Biology, Opole University, ul. Oleska 22, 45 - 052 Opole, Poland zatwar @ uni. opole. pl; https: // orcid. org / 0000 - 0003 - 2163 - 0143 zatwar@uni.opole.pl text Zootaxa 2024 2024-07-30 5487 1 1 100 http://dx.doi.org/10.11646/zootaxa.5487.1.1 journal article 10.11646/zootaxa.5487.1.1 1175-5334 13210771 50AC1672-FC20-4502-8D8A-4BCAE95F719B Genus Scatophila Becker Scatophila Becker 1896: 237–245 . Type species: Ephydra caviceps Stenhammar 1844 , by original designation.— Becker 1905: 212–214 [Palearctic catalog]; 1926: 86–91 [review of Palearctic species].— Cresson 1930: 128–131 [notes].— Sturtevant and Wheeler 1954: 183–201 [revision of Nearctic species ].— Wirth 1965: 758–759 [catalog of Nearctic species ]; 1968: 27–28 [catalog of Neotropical species].— Dahl 1959: 127–130 [review of Scandinavian species].— Papp 1975b: 123–128 [review of Hungarian species].— Cogan 1984: 169–171 [catalog of Palearctic species].— Zatwarnicki 1987: 277–298 [notes, synonymies of species].— Zatwarnicki and Mathis 1994: 351–370 [classification, phylogeny].— Mathis and Zatwarnicki 1995: 281–288 [world catalog]. Centromeromyia Frey 1954: 40 . Type species: Centromeromyia eremita Frey 1954 , original designation.—Zatwarnicki 1991: 329 [synonymy]. Diagnosis. Scatophila is distinguished from other genera of the tribe Scatellini by the following combination of characters: 1 fronto-orbital seta (some Neotropical species have 2); costa relatively short, extended to vein R 4+5 ; crossvein r-m distinctly distal to subcostal break. Description. Tiny to moderately small shore flies, body length 0.80–2.70 mm . Head : Frons dull usually with distinct, subshiny to shiny ocellar triangle; generally 1 fronto-orbital seta (some Neotropical species with 2). Antenna short, dark colored; pedicel setae typical; basal flagellomere round; arista almost bare, without long dorsal branches. Face projected, sometimes central portion membranous and distinctly incised or oral margin with a protruded, narrow, sometimes spine-like projection (sexual dimorphism is frequently evident in the conformation of the face); facial setae conspicuous, lateral facial setae ventrally curved, usually indistinctly from medial facial setae, inserted mostly in the middle and ventral portions of face, 4–8 setae on the oral margin. Eye nearly round or obliquely ovate. Genal seta generally present; genal height short to high, gena-to-eye ratio 0.14–0.55. Maxillary palpus elongate, mostly dark, yellow as an exception; proboscis of Scatophila is generally typical for Scatellini with rounded posterodorsal margin of the rostrum ( Fig. 3 ), and 5 pseudotracheae (as mentioned by Bolwig (1941) for S. unicornis Czerny ); pseudotracheal rings ended by attachments ( Tuxen (1944) called these “scrapers”); in most Scatellini the cibarium bears 2 dorsolateral parallel bands, as shown by Andersson (1967 , figs. 1 A –1C, page 109) and Zatwarnicki (2023 , fig. 23, page 668), which are reduced in Scatophila ( Fig. 4 ). FIGURES 3–5 . Morphological structures of Scatophila . 3. S. ordinaria Sturtevant & Wheeler , proboscis, lateral view. 4. S. ordinaria Sturtevant & Wheeler , cibarium, posterior view. 5. S. contaminata (Stenhammar) , head and thorax, dorsal view. Scale bar = 0.1 mm (3–4), 0.2 mm (5). Thorax : Mesonotum microtomentose, appearing with a multicolored pattern of bands and/or spots in many species; postsutural dorsocentral setae usually 2, rarely 3 (then with 1 presutural seta); acrostichal setae in 2 rows, extended to scutellum, equal in length; scutellum flat, disc bare, bearing 2 posterior setae laterally, basal scutellar setae smaller than apical setae; pleurae generally gray, lighter than mesonotum, posterior anepisternal seta well developed. Wing faintly to conspicuously infuscate with white spots distributed over most of wing, but exceptionally within cell r 1 ; costa short, extended to vein R 4+5 ; crossvein r-m distinctly distal to subcostal break; wings reduced in a few species; stem of halter short, head oval, white. Legs typical, usually without distinct setae (ventral row of spinulae on mid tibiae of males of some species); color of tarsi variable; tarsal claws conspicuously curved and pulvilli present below each claw. Abdomen: Tergites gray, microtomentose, sometimes with lighter posterior margins, or entirely shiny black. Male terminalia: Sternite 5 present, sternite 6 absent. Epandrium a closed plate; cercal opening circular to oval; cerci lunate to hemispherical; dorsal epandrial margin rounded, ventral epandrial margin straight or slightly convex to incised medially forming two lateral lobate process; phallapodeme elongate, curved or angular, sometimes with slightly raised keel; postgonites V-shaped, asymmetrical, usually sharply terminated posteriorly, sometimes bearing setae on dorsal margin of anterior portion; hypandrium, when present, as an inverted V-shaped structure bounded with the postgonites or as a more or less sinuous band; phallapodeme in lateral view shallowly curved or angulate, keel not evident or shallow, in ventral view usually T-shaped, with basal crossbar; aedeagus shoe-shaped in lateral view, in most species bearing narrow, un- or paired sinuous ventral process that originates from ventral side of distal aedeagal margin; ejaculatory apodeme lacking. Female Terminalia: sternite 8 divided, as 2 lateral, subquadrate sclerites, bearing a long seta on posterior margin; female cerci without prominent setae. Operculum of ventral receptacle helmet-like, somewhat round, covering extended process. Natural history.—Like most taxa included in the tribe Scatellini , the habitats where adults of Scatophila are found have sandy or muddy shores that are associated with lentic, freshwater systems, although some species are associated with inland alkaline or saline habitats. Deonier (1974) suggested that adults feed on algae and bacteria. Immature stages are known for only two species: Scatophila unicornis and Scatophila iowana ( Bolwig 1940a , Deonier 1974 ). Among shore flies, brachyptery is disproportionally expressed in species of the tribe Scatellini , including Scatophila , which has two described species with brachypterous wings: S. gorodkovi ( Krivosheina and Ozerov 2016 ; Russia . Chukotka : Wrangel Island. Mineeva Mountains; near lemming hole), and S. stenoptera ( Papp 1979 ; Papua New Guinea . Mount Wilhelm, slightly below Brass Tarn). In addition to these described species, at least two undescribed brachypterous species are known from the austral Neotropics. Discussion.— Scatophila currently comprises 50 species of which most occur in the Holarctic Region ( Mathis and Zatwarnicki 1995 and electronic updates). Zatwarnicki and Mathis (1994) proposed nine species groups for these species on a global basis, and of the nine species groups, five include species that are found in the Nearctic Region. The species groups were characterized primarily using structures of the male terminalia and these structures are likewise used extensively herein to recognize species. To facilitate the identification of species and to provide morphological evidence for how these species are classified, we provide detailed illustrations and descriptions of these structures, most for the first time. In addition, numerous photographs of key external characters are included. A key to the five species groups found in the Nearctic Region follows this discussion and is immediately followed by a key to the known Nearctic species. Key to Species Groups of Scatophila Occurring in the Nearctic Region based primarily on structures of the male terminalia 1. Aedeagus lacking a ventral process ( Figs. 13 , 20 , 29 , 36 )...................................................... 2 - Aedeagus with a ventral process, sinuous ( Figs. 44 , 55 , 63 , 70 , 80 , 88 , 99 , 106 , 118 , 124 , 136 , 144 , 155 , 166 , 174 , 182 , 190 , 201 , 207 , 214 , 228 , 235 )................................................................................ 3 2. Neohypandrium absent ( Figs. 28–29 ; 35–36 )................................................ The despecta Group - Neohypandrium present ( Figs. 12–13 , 19–20 )............................................. The contaminata Group 3. Fold on dorsal aedeagal opening convex with lateral processes ( Figs. 43 , 54 , 62 , 69 , 79 , 87 )....... The mesogramma Group - Fold on dorsal aedeagal opening generally angulate, sometimes incised medially, but without lateral processes ( Figs. 99 , 106 , 118 , 124 , 136 , 144 , 155 , 166 , 174 , 182 , 190 , 201 , 207 , 214 , 228 , 235 )............................................ 4 4. Fold on dorsal aedeagal opening incised medially or broadly semicircular ( Figs. 98 , 105 , 117 , 123 , 135 ); sometimes distal margin of epandrium with lateral processes or with broad medial projection ( Figs. 97 , 104 , 116 , 122 , 134 )..................................................................................................... The noctula Group - Fold on dorsal aedeagal opening with medial process or exceptionally flat ( Figs. 143 , 154 , 165 , 173 , 181 , 189 , 200 , 206 , 213 , 227 , 234 ), often distal margin of epandrium with sharp medial process, sometimes concave ( Figs. 164 , 180 , 188 , 199 , 205 , 233 )............................................................................. The quadriguttata Group Key to Nearctic Species of Scatophila (some couplets for males) 1. A presutural pair of dorsocentral setae present ( Figs. 175, 177 )................................................. 2 - Presutural dorsocentral setae lacking ( Fig. 5 , 10 , 22 , 31 , 45 , 58–60 , 74 , 89 , 107 , 119–121 , 137 , 145 , 156 , 176 , 202 , 217 , 223– 225 )................................................................................................ 3 2. Cell r 1 with 2–3 white spots; wing spots generally conspicuous ( Fig. 147 ); halter and basal tarsomeres pale; fronto-orbital plate not densely microtomentose ( Fig. 160, 162 )................................................. S. bisignata Cresson - Cell r 1 lacking spots; wing spots small and indistinct ( Fig. 158 ); halter and tarsi dark; fronto-orbital plate densely microtomentose, appearing velvety black ( Fig. 178 )..................................................... S. cribrata (Stenhammar) 3. Cell r 1 with 2 or more distinct white spots ( Figs. 109 , 204 )..................................................... 4 - Cell r 1 lacking spots, or with a single, weak, basal white area, or wings very pale, not appearing spotted ( Figs. 8–9 , 23–24 , 32–33 , 46–47 , 75–76 , 90–91 , 108 , 138–139 , 146 , 157 , 192–193 , 203 , 218–219 ).................................... 5 4. Scutellum with a distinct basal gray triangle ( Fig. 223 ); face of ♂ flat, the oral margin with 2–3 stout setae on each side, above them a cluster of smaller setulae arising from a brown area ( Figs. 215–216 )............... S. picta Sturtevant and Wheeler - Scutellum indistinctly marked ( Fig. 121 ); face of ♂ with a snout-like protuberance ventromedially ( Figs. 125–126 )............................................................................................ S. unicornis Czerny 5. Quadrate white spot of cell r 3 with a prominent dark center ( Fig. 218 ); face yellowish ( Fig. 221–222 )............................................................................................. S. pulchra Sturtevant and Wheeler - Large, quadrate white spot of cell r 3 lacking a dark center ( Figs. 8–9 , 23–24 , 32–33 , 46–47 , 75–76 , 90–91 , 108 , 138–139 , 146 , 157 , 192–193 , 203 , 219 ); facial coloration variable, dark to whitish gray ( Figs. 38–41 , 49–52 , 65–66 , 82–85 , 93–96 , 100–103 , 111–114 , 130–133 , 140–141 , 149–152 , 168–171 , 184–187 , 195–198 , 208–211 , 229–232 )............................ 6 6. Larger facial seta inserted toward posteroventral corner curved upward and outward ( Fig. 1 , 16–17 , 25–26 ), as in Scatella ; midfemora of ♂ bearing a row of short spine-like setae along posteroventral margin................................ 7 - Lower facial seta not oriented upward and outward ( Figs. 14 , 38, 40 , 49, 51 , 56 , 72 , 82, 84 , 93, 95 , 100, 102 , 111, 113 , 130, 132 , 195, 197 , 229, 231 ); midfemora of ♂ lacking row of spine-like setae............................................. 8 7. Epandrium diamond-shaped in posterior view, ventral third in posterior view conspicuously narrowed ( Fig. 27 ), width about equal to width of cercal cavity, ventral emargination shallow, rounded vertex; postgonites in ventral view nearly straight, tapered from wider base ( Fig. 28 ).......................................................... S. angusta sp. nov. - Epandrium ovate in posterior view with ventral third conspicuously wider than width of cercal cavity ( Fig. 34 ), ventral emargination wide, deeply and broadly V-shaped, vertex angulate; postgonites in ventral view conspicuously curved medially ( Fig. 35 )............................................................................ S. variabilis Cresson 8. Body tan, brown, or black, usually with some lighter markings, scutellar disc mostly dark but often with basal and sometimes with apical areas gray ( Figs. 5 , 10 , 45 , 58–59 , 74 , 89 , 107 , 119–120. 137 , 202 , 225 )................................. 9 - Body mostly whitish to grayish white, usually with some darker markings, scutellar disc mostly to entirely whitish ( Fig. 60 , 145 , 156 , 176 , 191 , 217 )............................................................................... 21 9. Body short, body length 1.10–1.60 mm , extensively blackish brown to black ( Fig. 5 ); tergites shiny black; knob of halter blackish; gena very short, gena-to-eye ratio 0.12 ( Fig. 7 )............................... S. contaminata (Stenhammar) - Body size variable but usually larger, mesonotum with some grayish areas ( Figs. 10 , 45 , 58–59 , 74 , 89 , 107 , 119–120. 137 , 202 , 225 ); tergites not entirely shiny; knob of halter pale, usually yellowish; gena higher, usually above 0.20 ( Figs. 15, 17 , 39, 41 , 50, 52 , 57 , 73 , 83, 85 , 94, 96 , 101, 103 , 112, 114 , 131, 133 , 196, 198 , 230, 232 )................................... 10 10. Acrostichal setae of uniform, small size, arranged in 2 regular rows ( Figs. 59 , 74 ); scutum generally tannish with scutal pattern not or barely evident.................................................................................. 11 - Acrostichal setae usually irregular in size and arrangement, rarely formed in 2 regular rows ( Fig. 10 , 45 , 58 , 89 , 107 , 119–120. 137 , 202 , 225 ), scutal pattern usually evident ( Fig. 10 , 45 , 58 , 89 , 107 , 119–120 , 137 , 202 , 225 )...................... 12 11. Epandrium with ventral margin widely concave, width much wider than width of cercal cavity ( Fig. 77 ), produced laterally as a thumb-like, short, process................................................. S. ordinaria Sturtevant and Wheeler - Epandrium with ventral margin truncate, width about equal to width of cercal cavity, not produced laterally ( Fig. 61 )............................................................................................ S. iowana Wheeler 12. A prescutellar pair of acrostichal setae well developed, subequal to length of ocellar setae ( Fig. 10 ); small species, length 1.40– 1.55 mm , scutal pattern gray ( Fig. 10 ); wings highly spotted ( Fig. 9 ); legs black; cephalic setae well developed ( Fig. 14–15 ); ♂ and ♀ with similar faces.................................................................... S. exilis Cresson - Presutural acrostichal setae at most slightly enlarged ( Fig. 45 , 58–59 , 74 , 89 , 107 , 119–120. 137 , 202 , 225 ); face of ♂ and ♀ sexually dimorphic, ♂ concave, flattened, protuberant, incised, tuberculate or otherwise modified from female type ( Figs. 38–41 , 49–52 , 82–85 , 93–96 , 100–103 , 111–114 , 195–198 , 229–232 )........................................... 13 13. Abdomen black, noticeably shiny, especially on posterior tergites, basal tergites at most thinly microtomentose.......... 14 - Abdomen brown to black, rather heavily microtomentose, rarely subshiny....................................... 18 14. Wing yellow at base, otherwise with a conspicuous pattern of white spots in largely infuscate remigium ( Fig. 33 ); scutellum with a distinct basal, gray triangle ( Fig. 58 ); face of ♂ flat to concave ( Figs. 49–50 ), the margin protuberant, grayish to more golden yellow............................................................. S. hesperia Sturtevant and Wheeler - Wing not strongly yellow at base ( Figs. 90–91 , 108 , 138 ); scutellum with indistinct basal, gray area or none ( Figs. 107 , 119– 120 , 137 ); face more brown than yellow, that of ♂ not shaped as above ( Figs. 93–94 , 100–101 , 111–112 , 130–131 )....... 15 15. Face of ♂ with a stout medial conical tubercle nearly as large as basal flagellomere ( Figs. 100–101 ), invested with setulae. Ventral epandrial margin essentially truncate, not bifurcate medially or with ventrolateral extensions.......................................................................................... S. hirtirostris Sturtevant and Wheeler - Face of ♂ not as above ( Figs. 93–94 , 111–112 , 130–131 ). Ventral epandrial margin with ventrolateral extensions or bifurcate medially........................................................................................... 16 16. Scutum subshiny ( Figs. 107 , 137 ); tarsi often yellow basally; face of ♂ brown, protuberant at ventral margin, with an elongate, medial depression bordered by dense curly setulae ( Figs. 93–94 , 130–131 ), especially laterally; face of ♀ with some subshiny luster ( Figs. 95–96 , 132–133 ); ventral epandrial margin with ventrolateral extensions, these narrow ( Figs. 97 , 134 )....... 17 - Scutum wholly densely microtomentose, appearing dull ( Fig. 120 ); tarsi mostly brown or black; face of ♂ with a low medial ridge invested with fine setulae ( Figs. 111–112 ); face of ♀ brown, microtomentose, not subshiny or lustrous ( Figs. 113–114 ); ventral epandrial margin bifurcate medially, each lateral lobe robustly developed ( Fig. 115 )......... S. tuberculosa Cresson 17. Epandrium with ventrolateral extensions small, narrow, length about equal to width of a cercus ( Fig. 97 ); aedeagus in ventral view ( Fig. 98 ) pentagonal; keel of phallapodeme small, thumb-like................................ S. bolwigi sp. nov. - Epandrium with ventrolateral extensions large, length equal to height of a cercus ( Fig. 134 ); aedeagus in ventral view ( Fig. 135 ) rectangular; keel of phallapodeme robust, length almost as long as either arm of phallapodeme.............................................................................................. S. variofacialis Sturtevant and Wheeler 18. Distance between reclinate fronto-orbital seta and medial vertical seta subequal to that between inner and lateral vertical setae ( Figs. 38, 40 ); tarsi usually, and sometimes tibiae, pale; face of ♂ with medial indentation at margin ( Fig. 38 ) and bearing cluster of long setulae and setae on each side................................................. S. adamsi Cresson - Reclinate fronto-orbital farther from medial vertical seta than the latter is from the lateral vertical seta ( Fig. 84 , 195, 197 , 229, 231 ); tarsi usually dark but paler in viridella ; face of ♂ not as above ( Figs. 82–83 , 195–196 , 229–230 )................. 19 19. Gena about as high as width of basal flagellomere ( Fig. 83, 84 ); frontal triangle scarcely differentiated in color from anterior non-fronto-orbital plate ( Fig. 82, 84 ); scutum usually with an olive tint ( Fig. 89 ); maxillary palpus pale; tarsi usually partially pale..................................................................... S. viridella Sturtevant and Wheeler - Gena shorter than width of basal flagellomere ( Figs. 196, 198 , 230, 232 ); frontal triangle and fronto-orbital plate dull brown, leaving black triangular areas along anterior margin of frons ( Figs. 195, 197 , 229, 231 ); maxillary palpus and tarsi mostly dark............................................................................................... 20 20. Scutum with medial anterior dark stripe almost black ( Fig. 202 ), pale areas on each side of it scarcely visible; dorsum of postpronotum noticeably microtomentose; face of ♂ flat in center, never membranous, the oral margin rather straight ( Figs. 195–196 ).................................................................. S. hirsuta Sturtevant and Wheeler - Scutum with medial anterior dark stripe not much darker than other markings ( Fig. 225 ); pale marks over postpronotum continuous with dorsal marks on each side of medial stripe; face of ♂ sunken in middle, usually membranous to a noticeable degree; oral margin protuberant ( Figs. 229–230 ).............................. S. rubribrunnea Sturtevant and Wheeler 21. Wings mostly pale, whitish, a spotted pattern scarcely evident ( Fig. 47 ); gena broad, more than twice as wide as width of basal flagellomere ( Fig. 66 ); coastal species................................................... S. mesogramma (Loew) - Wings darker, a spotted pattern usually evident ( Figs. 139 , 146 , 192 , 203 ; but pale in S. conifera , Fig. 157 ); gena narrower than above ( Figs. 141 , 150, 152 , 169, 171 , 185, 187 , 209, 211 ); western to southwestern species.......................... 22 22. Face of ♂ flat or concave in middle ( Fig. 145 , 184–185 ); pedicel thickly setulose along medial margin................. 23 - Face of ♂ prominently convex medially ( Fig. 149–150 , 168–169 , 208–209 ); pedicel with sparse setulae; face of ♀ without a pair of divergent setae on upper carina ( Figs. 151–152 , 170–171 , 210–211 )...................................... 24 23. Face of ♂ flat to slightly concave medially, not membranous ( Fig. 145 ); 2–3 facial setae along margin at each side rather pale and weak; coloration nearly uniformly whitish, abdomen mostly whitish microtomentose; face of ♀ silvery gray, gena wider than width of basal flagellomere ( Figs. 140–141 )............................................. S. arenaria Cresson - Face of ♂ concave, membranous medially behind oral margin ( Fig. 184–185 ); 2–3 stout black setae on each side stronger than those of S. arenaria ; less whitish, especially on abdomen; face of ♀ with a pair of divergent setae on upper carina ( Figs. 186–187 )............................................................................. S. disjuncta Cresson 24. Face of ♂ evenly arched in middle ( Figs. 149–150 ), thickly setulose, especially 2 large lateral clusters in which 3–5 are stronger; wing spots distinct, including apical spot of cell r 3 ( Fig. 146 ); face of ♀ gray with some brownish discoloration ( Figs. 151–152 )................................................................ S. bipiliaris Sturtevant and Wheeler - Face of ♂ protuberant, medial portion forming a broad cone that involves the oral margin ( Figs. 168–169 , 208–209 ), broad cone surrounded by clustered setae except at margin; wing spots rather indistinct ( Figs. 157 , 203 )......................... 25 25. Facial protuberance of ♂ pronounced ( Fig. 208–209 ), bearing numerous prominent curved black setulae, postgonite in ventral view ( Fig. 206 ) with basal margin excavated, very broadly V-shaped; phallapodeme in ventral with crossbar shallowly concave............................................................................. S. mystacina sp. nov. - Facial protuberance of ♂ and setulae on each side of protuberance smaller ( Figs. 168–169 ). Postgonite in ventral view ( Fig. 173 ) with basal margin sloped toward apex, not excavated; phallapodeme in ventral with crossbar nearly straight, not concave........................................................................ S. conifera Sturtevant and Wheeler