Tritoxa flexa (Wiedemann)

Sinclair, Bradley J., Macleod, Alyssa M. & Wheeler, Terry A., 2021, Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae), Zootaxa 4920 (3), pp. 359-379 : 367-371

Tritoxa flexa (Wiedemann)

( Figs 1 , 9 , 18 , 20, 21 , 26 )

Trypeta flexa Wiedemann, 1830: 483 . Type locality: “Neugeorgien” [= USA, Georgia].

Trypeta arcuata Walker, 1853: 383 . Type locality: USA ( Loew, 1873: 102, synonym).

Tritoxa flexa ( Wiedemann, 1830) : Loew, 1873: 102 (new combination).

Type material. HOLOTYPE ♀ ( Fig. 20 ): Georgia [32°09′56″N 82°54′00″W] (See Fig. 21 for label details) ( ZMHB).

Additional material examined. CANADA. Manitoba: Aweme [49°43′N 99°36′W], 23.vii.1913, 20, 23. vii.1915, 16.viii.1916, 24.viii.1917, 4,8. vii.1924, M. Criddle (3♂, 3♀, CNC; 1 ♀, DEBU) ; same data except, 27.vi.1921, 4.vii.1924, R.M. White (1♂, 1♀, CNC) ; Bald Head Hills [49°40′52″N 99°18′20.9″W], 13 mi. N Glenboro, 18.viii.1958, J.G. Chillcott (1♀, CNC) ; Bald Head Hills , 12 km N Glenboro, 4.viii.1983, K.N. Barber (1 ♂, 1 ♀, DEBU) ; Deloraine [49°11′N 100°29′W], 2.vii.1927, E. & S. Criddle (1♂, CNC) ; Douglas [49°53′N 99°42′W], 10.vi.1921, P. Vroom (1♂, CNC) ; 15 mi N Glenboro , 11.vii.1958, J.G. Chillcott (1♀, CNC) ; Oak Lake [49°45′N 100°37′W], 11.vii.1953, Brooks & Kelton (1♀, CNC) ; 5 mi. SW Shilo [49°48′N 99°38′W], 13.viii.1958, J.G. Chillcott (2♀, CNC) ; St. Charles Rifle Range, Winnipeg , 49°54.2′N 97°20.3′W, 8.vii.1998, tallgrass prairie, P. Bouchard (1♂, LEM) ; St. Lazare [50°26′N 101°18′W], 15.viii.1954, Brooks & Kelton (1♂, CNC) . Ontario: Manitoulin Is., Christina Bay [45°49′N 82°55′W], 25.vi.1994, G. Vogg (1♀, DEBU) ; One Sided Lake [not plotted, locality unconfirmed], 30.vii.1960, S.M. Clark (1♂, 1♀, CNC) ; Pelee Is. [41°45′N 82°37′W], 12.ix.1961, Kelton & Brumpton (1♀, CNC) ; Pelee Island, sweep at Stone Rd. Alvar, 10.vi.1993, B. Larson (2♂, 4♀, DEBU) ; same data except, Alvar FON Res. , 41°45′20″N 82°37′54″W, 8.vi.2002, S.A. Marshall (4♂, 2♀, DEBU) ; same data except, 8– 9.vi.2002, S.M. Paiero (1♂, 1♀, DEBU) ; same data except, prairie, yellow pans, 8–9.vi.2002, Paiero & Buck (1♀, DEBU) ; same data except, 41°47′N 82°40′W, 1.x.2000, S.A. Marshall (1♀, DEBU) ; same data except, 1.x.2000, S.A. Marshall (3♂, DEBU) ; same data except, Blue Ash Savanna , 16.vii.1995, J. Skevington (4♂, 4♀, DEBU) ; same data except, 41°45.3′N 82°37.9′W, 8.vi.2002, K.N. Barber (1♀, DEBU) ; same data except, 30.vii.1998, B. Larson (1♀, DEBU) ; Pelee Island , 14.vi.2018, K.H. Stead (2♂, DEBU) . Saskatchewan: Arcadia , 4.vii.1938, W.B. Fox (1♂, CNC) ; Estevan [49°08′N 102°59′W], 15.viii.1955, A. R. Brooks (1♀, CNC) . USA. Connecticut: Milford [41°13′N 73°03′W], ix.1943, soy beans (2♂, USNM) ; New Haven [41°18′N 72°55′W], 10.i.1939, S.C. Ball (1♀, USNM) . Illinois: Chicago [41°52′N 87°37′W], 27.v.1911 (1♂, USNM) . Indiana: Lafayette [40°25′N 86°52′W], 1923, G.M. Stirrett (1♀, CNC) . Iowa: Ames [42°02′N 93°37′W], 19.vi.1947, A. R. Brooks (1♂, 1♀, CNC) ; same data except, 16,23. vii.1930, H.M. Harris (3 ♂, 4 ♀, DEBU) ; Moravia [40°53′26″N 92°48′57″W], 20.vii.1969, C.A. Toff (1♂, USNM) ; Pleasant Valley [41°41′N 86°04′W], 23.vi., 5.vii.1928, G.S. Walley, ex onions (5♂, 2♀, CNC) . Maryland: Anne Arundel Co., 6 km S Edgewater , 38°53′N 76°33′W, 25.v.1976, J.H. Falk (2♂, USNM) ; Anne Arundel Co. [39°00′N 76°36′W], CBCES, 12.x.1976, J.H. Falk (1♀, USNM) ; Baltimore Co. [39°24′N 76°36′W], 22.x.1967, C.F. Reed (2♂, 5♀, USNM) ; Bradshaw [39°25′N 76°22′W], Rte 40, 3.vii.1965, W. Boyle (1♀, LEM) ; Cabin John [38°58′N 77°9′W], 21.v.1944, G.E. Bohart (1♂, CAS) ; Calvert Co. [38°32′N 76°32′W], Rte 416, 24.ix.1961, R. A. Boett (1♂, USNM) ; Calvert Co., Lusby [38°21′N 76°26′W], 3.viii.1969, G. Steyskal (1♀, USNM) ; Colesville [39°4′N 77°0′W], 5,20,28. viii.1975, 1.viii.1976, 4.vi.1977, W.W. Wirth (4♂, 2♀, USNM) ; Howard Co., Clarksville [39°12′N 76°56′W], 12.ix.1981, N.E. Woodley (1♀, USNM) ; Montgomery Co., Rockville [39°5′N 77°8′W], 20.v.1979, S.W. Gross (1♀, USNM) ; Plummers Is. [38°58′10″N 77°10′35″W], 27.ix.1949, G.E. Shewell (1♀, CNC) ; Prince George’s Co., College Park [38°59′N 76°55′W], 8.viii.2001, P.H. & M.M. Arnaud (1♀, CAS) ; Prince George’s Co., Beltsville [39°2′N 76°55′W], 16–26.x.1964, P.H. Arnaud (1♂, 1♀, 1?, CAS) ; Prince George’s Co., Oxon Hill [38°48′N 76°59′W], 28.vi.1971, G.F. Hevel (1♂, USNM) ; Prince George’s Co., Patuxent Research Station [39.06°N 76.78°W], 24.viii.1986, N.E. Woodley (1♂, USNM) ; Prince George’s Co., Cedarville SP, 38°38′N 76°48′W, 24–29.vii.2008, S.M. Paiero (1 ♂, DEBU) ; Thurmont [39°37′N 77°24′W], 8.vi.1962, J. R. Vockeroth (1♂, 3♀, CNC) . Michigan: Ann Arbor [42°16′N 83°44′W], 11.iv.1942, A. Peterson (1♀, 1?, UNSM) ; Detroit [42°19′N 83°02′W], 6.vi.1940, 28.vi.1942, G. Steyskal (2♂, USNM) . Minnesota: Wilkin Co. [46°22′N 96°28′W], vi.1921, C.W. Howard (1♀, USNM) . Mississippi: Lafayette Co. [34°22′N 89°29′W], no date, F.M. Hull (1♂, CNC) . Missouri: 25 mi. S St. Louis [38°37′N 90°11′W], 3.viii.1965, H. Hoek & J. Lovely (1♀, LEM) . Nebraska: Lincoln [40°48′N 96°40′W], 13.vi.1924, no collector (1♂, USNM) . New Jersey: Marlboro [40.342°N 74.257°W], 4.vii.1962, J. Tomlinson, L. Davenport (1♂, 4f, CAS) ; Moorestown [39.977°N 74.944°W], 8.viii.1927, J.E. Holloway (1♂, USNM) ; Princeton [40.357°N 74.670°W], x.1901, A.H. Sturtevant (1♀, USNM) ; Riverton [40.011°N 75.014°W], 6.ix.1927, C.H. Ballou (1♂, USNM) . New York: New York City [40°39′N 73°56′W], 11.iv.1939 (1♂, CAS) . Ohio: Columbus [39°57′N 83°00′W], 25.viii.1916, A.J. Bosinger (1♂, CAS) . Pennsylvania: Bryn Mawr [40°01′N 75°19′W], vi.1913, A.H. Sturtevant (1♂, USNM) ; Centre Co., Scotia Barrens [40°47′N 77°51′W], 13.ix.1972, 21.vii.1973, D.D. Wilder (2♀, CAS) ; same data except, 19.vii.1973, D.J. Shetlar (3 ♂, CAS) ; Franklin Co., Chambersburg [39°56′N 77°39′W], 9.viii.1972, S.S. Maxwell (3♂, 1♀, CAS) ; Lebanon Co., Indiantown Gap [40°26′N 76°34′W], 26.vi.1973, D.D. Wilder (1♀, CAS) ; Perry Co., Buffalo Bridge [40°29.38′N 77°09.48′W], 5.x.1968, J.W. Adams (1♂, USNM) ; Perry Co., nr Millerstown [40°33′N 77°09′W], 17.viii.1968, J.W. Adams (1♀, USNM) ; York Co., 5 mi. NW Davidsburg [39°59′N 76°53′W], 1.vii.1961, P. Spangler (1♂, USNM) ; Wyoming, Philadelphia [40°00′36″N 75°06′58″W], 4.vii.1904, G.M. Greene (1♂, USNM) . Tennessee: Davidson Co., Nashville [36°10′N 86°47′W], 4.vii.1982, P.H. Arnaud (1♀, CAS) ; Roane Co., nr Rockwood [39°54′N 79°09′W], 8.v.1979, K.A. Spencer & G.C. Steyskal (1♂, USNM) . Virginia: Botetourt Co., Jefferson Mtn Pk , 37°32′14″N 79°58′31″W, 588 m, 22.v.1999, S. Paiero (1♂, DEBU) ; Emporia [36°41′N 77°32′W], 7.v.1973, G.C. Steyskal (1♂, 1♀, USNM) ; Fairfax Co., Fairfax [38°51′N 77°18′W], 12.x.1974, R. W. Baumann (1♂, USNM) ; Fairfax Co., Great Falls [38°59′N 77°17′W], 11.vi.1944, G.E. Bohart (2♂, 1♀, CAS) ; same data except, 23.ix.1956, P.H. Arnaud (1♀, CSCA) ; Hawksbill [38°33′N 78°23′W], Shenandoah NP, 3600–4050 ft, 7.vi.1962, J. R. Vockeroth (5♂, 3♀, CNC) ; Shenandoah NP; Natural Bridge [37°37′N 79°32′W], 7.vi.1962, J. R. Vockeroth (1♂, CNC) . Washington DC: [38°54′N 77°00′W] 19.vi.1938, J.F.G. Clarke (1♀, USNM) ; same data except, 25.vi.1944, G.E. Bohart (1♀, CAS) ; Rock Creek Park, Military Field Meadow [38°57′N 77°2′W], 16.viii.1978, R. A. Boettche (1♀, USNM) . West Virginia: Morgantown [39°38′N 79°57′W], 10.vi.1964, O. Peck (1♀, CNC) ; Morgan Co., Cherry Run , 6 mi. NW Hedgesville [39°33′N 77°59′W], 1.ix.2001, P.H. & M.M. Arnaud (1♀, CAS) . Wisconsin: Milwaukee [43.05°N 87.95°W], iv.1910, no collector (1♀, USNM) .

Diagnosis. Tritoxa flexa is characterized by its dark brown to black body and broad, dark-brown wings, with a narrow and arched subapical hyaline crossband and inner surstylus with evenly space large prensisetae.

Redescription. Entirely dark brown to black ( Fig. 1 ). Head: ocellar triangle shiny black; frons reddish-brown to brown; silvery parafrontal microtrichose stripe very narrow, continuous with very narrow microtrichose parafacial; gena slightly darker below narrowest part of lower eye margin; postocular microtrichia wider than parafrontal microtrichia in lateral view, extending from base to middle of eye; face dark brown; supracervical setulae pale.

Antenna with postpedicel dark brown to black, sometimes yellowish brown on ventral and basal surfaces. Proboscis with dark brown palpus. Thorax: dark brown to black; scutum mostly thinly microtrichose with pair of faint microtrichose vittae; lateral margin of scutum and postpronotal lobe broadly shiny; scutellum concolourous with scutum; mediotergite without distinct stripe; pleura shiny, anepisternum and katepisternum lightly clothed in whitish microtrichia when viewed obliquely; whitish microtrichia above fore coxa; 1 anepisternal seta. Wing ( Fig. 9 ) broadly rounded and slightly enlarged apically; entirely dark brown to black without faded regions; costal cell without narrow hyaline band at humeral break, with hyaline band at apical fourth in line with discal hyaline crossband; hyaline area from apical region of Sc to R 1; oblique subbasal hyaline crossband reaching two-thirds length of cell dm to nearly wing margin; discal hyaline crossband oblique, long, arched, extending to posterior distal corner of cell dm, sometimes slightly beyond cell; subapical hyaline crossband narrow, nearly straight to arched, anterior end extending proximal to crossvein r-m; crossvein dm-m sinuous; anal lobe somewhat developed; calypter with brown margin. Abdomen: black. Male terminalia ( Fig. 18 ): inner surstylus with 6–8 thick prensisetae distributed along straight inner margin; outer surstylus slender, longer than inner surstylus, arched mesally with rounded apex; subepandrial sclerite with scattered dark, stiff setae. Cercus with long apicolateral setae; apical margin straight. Phallus long, with 4–5 loops.

Distribution. Tritoxa flexa is widespread in eastern North America, from southeastern Saskatchewan and southern Manitoba to Mississippi. In eastern Canada, this species is only known from Manitoulin and Pelee Islands in Ontario ( Fig. 26 ). Additional records include sites from Alabama, North and South Carolina and Massachusetts based on images from BugGuide and iNaturalist.

Remarks. Tritoxa flexa has received more attention than congeners due to its higher economic importance. Its main host plant is the commercial onion, Allium cepa L., though larvae may also feed on wild garlic. The larva was first described and illustrated by Banks (1912). Chittenden (1927) provided a brief description of the adult and larval stage and summarized reports of its injurious nature. One parasitoid is known for this pest, Tachinaephagus zealandicus Ashmead ( Downing 1973) . Tritoxa flexa breeds from late spring to early summer and completes two and a partial third generations per year, with larvae and pupae overwintering ( Downing 1977). Manis (1941) also described the biology of this species and the mature larva was described and illustrated by Peterson (1960). In areas where the ranges of T. flexa and T. incurva overlap, and where the latter species completes two generations per year, competition on wild garlic may occur in the month of September ( Downing 1977).

Figures

FIGURES 1–2. Photographs of living Tritoxa species. 1. T. flexa (Madison County, Tennessee); 2. T. incurva (Madison County, Tennessee). Photographs @ Ken Childs.

FIGURES 6–13. Wings of Tritoxa species. 6. T. californica sp. nov.; 7. T. cuneata; 8. T. decipiens sp. nov.; 9. T. flexa; 10. T. incurva; 11. T. pollinosa; 12. T. ra; 13. Tritoxa sp. Abbreviations: d bd—discal band; dm—discal medial cell; dm-m—discal medial crossvein; r-m—radial medial crossvein; sbap bd—subapical band; sbb bd—subbasal band.

FIGURES 18–19. Male terminalia of Tritoxa species, posterior view. 18. T. flexa; 19. T. incurva.

FIGURES 20–21. Holotype of Tritoxa flexa, coll.mfn-berlin.de_u_c2e921 (ZMHB). 20. Habitus, lateral view; 21. Type labels.

FIGURES 24–26. Distribution of Tritoxa species. 24. T. californica sp. nov. (incl. unconfirmed records (red open circles)) and Tritoxa sp.; 25. T. decipiens sp. nov.; 26. T. cuneata and T. flexa.