Acerocnema fasciventris ( Malloch, 1920 )

Chagnon, Marie-Eve & Sinclair, Bradley J., 2021, Revision of Nearctic species of Acerocnema Becker (Diptera: Scathophagidae), Zootaxa 4952 (3), pp. 523-539 : 525-527

Acerocnema fasciventris ( Malloch, 1920)

( Figs 1, 2 , 9, 14 , 15 , 19 , 23 )

Gimnomera fasciventris Malloch, 1920: 38 . Type locality: Meredosia, Illinois, USA.

Gimnomera fasciventris: Vockeroth, 1965: 840 .

Acerocnema fasciventris: Chagnon & Sinclair, 2020: 372 (new combination).

Type material examined. HOLOTYPE ♂, labelled: “ INHS / Insect Collection/ 238,602 [white label]”; “Meredosia, Ill [39°49′48″N 90°33′30″W]/ May 20, [19]17”; “Type/ Gimnomera / fasciventris/ ♂ Malloch [red label]”; “Gimnomera/ fasciventris/ Mall type”; “ Acerocnema / fasciventris/ det. M.-E. Chagnon 2018” ( INHS) . ALLOTYPE: “ INHS / Insect Collection/ 238, 601 [white label]”; “Meredosia, Ill/ May 29, [19]17”; “ Allotype / Gimnomera / fasciventris/ ♀ Malloch [blue label]”; “ Acerocnema / fasciventris/ det. M.-E. Chagnon 2018” (1♀, INHS) . PARATYPE: “Meredosia, Ill/ May 29, [19]17”; “ Paratype / Gimnomera / fasciventris/ ♀ Malloch [blue label]”; “ INHS / Insect Collection/ 713,428 [white label]”; “ Acerocnema / fasciventris/ det. M.-E. Chagnon 2018” (1♀, INHS) .

Additional material examined. CANADA. British Columbia: 10 km W Kamloops , 50.643° -120.517°, 13.vi.2013, Malaise, C. Simon, BIOUG07043 -H02 (1♀, barcode associated, CBG) ; same data except, 50.663° - 120.504°, 11.vii.2013, BIOUG07943 -B11 (1♀, barcode associated, CBG) ; Mount Revelstoke National Park , 51.018° -118.205°, 26.vi.2014, Malaise, S. Devita, BIOUG19445 -E10 (1♀, barcode associated, CBG) ; same data except, BIOUG19445 -F02 (1♀, barcode associated, CBG) ; same data except, BIOUG19538 -H03 (1♀, barcode associated, CBG) ; Summit Lake [58°39.054′N 124°39.089′W], 4500 ft, 26–27.vi.1959, E.E. McDougall (1♂, CNC) [homotype compared to type by Vockeroth 1963]; same data (1♀, CNC) ; Summit Lake [58°39.054′N 124°39.089′W], 4500 ft, 23–24.vi.1959, E.E. MacDougall (1♂, CNC) . Newfoundland and Labrador: Goose Bay, 53.21408° - 60.45044°, Repl. 2 wet, Malaise , 18–21.vi.2010, NBP Field Party (1♂, LEM) , same data except, CCBD-33863-G10 (1♀, barcoded [sequence not available], LEM) . Northwest Territories: Yellowknife, 62.51591° -113.39146°, 230 m, Repl. 3 wet, Malaise , 15–18.vi.2011, NBP Field Party (1♀, LEM) . Ontario: Elizabethtown , 44.621°, -75.773°, 17.vi.2010, J. Sones, BIOUG00866 -B06 (1♀, barcode associated, CBG) ; Frontenac Co., Cranberry Lake, Runtz Property , 44.441111°N 76.290556°W, 18–24.v.2007, Malaise, J. Skevington, H. Douglas, D. Runtz (1♀, 3♂, CNC) ; 7 km E Griffith [45°14′38.5″N 77°09′58.7″W], 8.vi.1990, B.E. Cooper (1♀, 2♂, CNC) ; Metcalfe [45°13′13.7″N 75°27′53.0″W], 14.vii.1981, B.E. Cooper (1♀, CNC) ; Mer Bleu [45°23′36.9″N 75°30′43.1″W], Malaise, 7.vii.1966, D.D. Munroe (1♂, CNC) . Quebec: Mont St. Hilaire, 45°32′N 73°09′W, 25.v.2001, T. A. Wheeler (1♂, LEM) . Saskatchewan: Cantyre , 53°23′N 101°50′W, 12.ix.1959, J. R. Vockeroth (3♀, CNC) . Yukon: Dempster Hwy, nr North Fork Pass, 64.59736° -138.31009°, 1180 m, Repl. 2 wet, Malaise , 24–27.vi.2011, NBP Field Party, CCDB-21325- G09 (1♀, 1♂, barcoded, LEM) ; Dempster Hwy, nr North Fork Pass, 64.59915° 138.30611°, 1216 m, Repl. 2 mesic, Malaise , 24–27.vi.2011, NBP Field Party, CCDB-21325-G10 (1♀, barcoded, LEM) ; km 416 Dempster Hwy [64°35′50.496″N 138°18′36.324″W], 750 m, 22–28.vi.1980, Wood & Lafontaine (6♂, CNC) ; N Whitehorse, 60.841° -135.208°, 6.vii.2014, Malaise, M. Whitley, BIOUG25710 -G12 (1♀, barcode associated, CBG) . USA. Maryland: Laurel [39°05′42.3″N 76°51′01.0″W], 10.v.1967, D. R. Smith (1♀, USNM) ; Plummers [38°58′9″N 77°10′36″W], 23.iv.1914, R.C. Shannon (1♀, USNM) . Pr. Frederick, Scientist Cliffs [38°31.043′N 76°30.793′W], 16–17.iv.1977, Wood & Shewell (7♂, CNC) . Texas: Kerrville [30°02′53.7″N 99°08′35.7″W], 7.iv.1959, Becker & Howden (1♀, CNC) . Virginia: Chain Bridge [38°55′45.0″N 77°05′49.2″W], 14.v.1922, J. R. Malloch (1♀, USNM) .

Diagnosis. This species is distinguished by the presence of several dorsal preapical setulae on R 1, dark postpedicel, pale setae and 4–5 inclinate frontal setae and 2 proclinate orbital setae.

Redescription. Male. Body primary colour brown/ yellow; pleura brown; scutum brown; entire body pruinose, expect apex of scutellum. Setae on head yellow brown.

Head with face yellow and gena yellow; genal width 1/3 eye height; postgena yellow; postocellar triangle brown. Frontal vitta yellow; fronto-orbital plate black transitioning to yellow anteriorly; parafacial yellow. Fronto-orbital plate with 4–5 inclinate frontal setae, 2 proclinate and 1 lateroclinate orbital setae, 1 pair of long lateroclinate ocellar setae, 1 pair of divergent postocellar setae shorter than ocellar setae, 1 pair of paravertical setae, 1 long inclinate inner vertical seta, 1 lateroclinate outer vertical seta, shorter in length than inner vertical seta. Vibrissa strong, with 4 variably lengthened subvibrissal setae, none subequal to vibrissa. Antenna with postpedicel black, about five times as long as pedicel; scape and pedicel black; arista black, pubescent, same length as dorsal surface of flagellomere. Palpus yellow with pale setae apically.

Thorax with scutal setae yellow; acrostichal setae biserial, finer than dorsocentrals, but distinct; 3 presutural and 4 postsutural dorsocentral setae; 2 posterior postpronotal setae; 1 intra-postpronotal seta; 2 presutural intra-alar setae; 2 notopleural setae; 1 postsutural intra-alar seta; 2 postsutural supra-alar setae; 2 postalar setae; 2 pairs of scutellar setae. Pleura with 1 yellow proepisternal seta; 1 yellow proepimeral seta; 3 posterior anepisternal setae and several long anepisternal setulae, all yellow; 1 yellow posterodorsal katepisternal seta; anterior half of anepisternum and anepimeron without setulae, katepisternum with setulae ventrally.

Wings (length 2.6–2.7 mm) clear, lightly infuscate, R 1 with singular row of 4 setulae on apical fourth; CuA+CuP ending just before wing margin. Halter white or yellow.

Legs entirely yellow. Setae on legs yellow. Fore femur with white ventral pile and 1 preapical posterodorsal seta. Fore tibia with 1 mid dorsal seta and 1 preapical dorsal seta. Mid femur with white ventral pile; 1 preapical dorsal seta. Mid tibia with 1 preapical ventral seta and 1 preapical posteroventral seta. Hind femur with white ventral pile. Hind tibia with 1 preapical anterodorsal seta; 1 preapical posterodorsal seta; 3 anterodorsal setae on basal half and 3 posterodorsal setae on basal half. Tarsi yellow with ventral pile.

Abdominal tergites black to pale brown, with pale setulae over surface. Abdominal sternites brown. Sternite 5 enlarged, yellow and rectangular, with 2 large divergent apically rounded processes; lobes with scattered thick setae, longer at base ( Fig. 9 ).

Terminalia ( Figs 1, 2 ) with epandrium black; surstylus yellow, with apical perimeter black; cercus yellow; hypandrium yellow. Epandrium on dorsal surface of abdomen, surstylus, cercus and tergite 5 all jutting out from ventral surface of abdomen. Surstylus long and slender, apically expanded with rounded margin; setae along inner apical margin and scattered on inner face of shaft. Cercus small, composed of two sclerotized sections: dorsal section with thinly sclerotized oval lobe with short scattered setae; ventral section with right angled bent lobe bearing inner ventral tuft of setae, longer than lobe; lobe with serrated upper margin and truncate apex. Pregonite unforked, uniformly slim with seta along slightly expanded apex. Postgonite similar to pregonite but apical end slightly more enlarged without setae. Epiphallus partially sclerotized, arched to narrow apex; shorter than postgonite.

Female. Similar to male, except abdomen mostly yellow with dorsal surface dark; terminalia as in generic diagnosis ( Fig. 14 ).

Distribution. This is a transcontinental species with a southern population in Texas ( Fig. 23 ).

Remarks. During a revision of the Nearctic species of Gimnomera ( Chagnon & Sinclair 2020) , no specimens of G. fasciventris were present under this genus in the CNC. Upon receipt of the types of G. fasciventris from INHS, the specimens keyed out to Acerocnema using the key to genera in Vockeroth (1987). Upon comparison with specimens of Acerocnema in the CNC, a unit tray of fasciventris specimens bearing Vockeroth’s determination label was discovered, including a “homotype” dated 1963 (i.e., a specimen directly compared by Vockeroth and considered conspecific to the type at INHS). Based on this discovery it was surmised that Vockeroth had come to the same conclusion that fasciventris should be transferred from Gimnomera to Acerocnema , but he never formally published this new combination ( Chagnon & Sinclair 2020). It was this new information that spurred our revision of this genus.

Figures

FIGURES 1–4. Male terminalia of Acerocnema. 1. A. fasciventris (Malloch), posterior view; 2. same, lateral view; 3. A. merga sp. nov., posterior view; 4. same, lateral view.Abbreviations: an—anus; cerc—cercus; d sec cerc—dorsal section cercus; epand—epandrium; hypd—hypandrium; pgt—postgonite; sur—surstylus; v sec cerc—ventral section cercus.

FIGURES 9–14. Male and female Acerocnema. 9. A. fasciventris (Malloch), male sternite 5, ventral view; 10. A. merga sp. nov., pregonites and postgonites, lateral view; 11. A. merga sp. nov., male sternite 5, ventral view; 12. A. rufula (Curran), male sternite 5, ventral view; 13. A. vanga sp. nov., male sternite 5, ventral view; 14. A. fasciventris (Malloch), female abdomen, lateral view. Abbreviations: cerc—cercus; epiph—epiphallus; epiprct—epiproct; hyprct—hypoproct; pgt—postgonite; ph—phallus; pregt—pregonite.

FIGURES 15–18. Acerocnema male species, habitus lateral views. 15. A. fasciventris (Malloch); 16. A. merga sp. nov.; 17. A. rufula (Curran); 18. A. vanga sp. nov.

FIGURES 19–22. Acerocnema female species, habitus lateral views. 19. A. fasciventris (Malloch); 20. A. merga sp. nov.; 21. A. rufula (Curran); 22. A. vanga sp. nov.

FIGURES 23–26. Known distribution of Acerocnema. 23. A. fasciventris (Malloch); 24. A. merga sp. nov.; 25. A. rufula (Curran); 26. A. vanga sp. nov.