Tritoxa incurva Loew, 1873

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 : 371-373

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Tritoxa incurva Loew


Tritoxa incurva Loew

( Figs 2 View FIGURES 1–2 , 3 View FIGURES 3–5 , 10 View FIGURES 6–13 , 19 View FIGURES 18–19 , 27 View FIGURES 27–29 )

Tritoxa incurva Loew, 1873: 104 . Type locality: Illinois, USA.

Type material examined. LECTOTYPE ♂ [ MCZ: Ent :13247], labelled: “Ill. [Illinois, 40.0417°N 89.1965°W]”; “illegible/ Shimer”; “Loew/ Coll.”; “incurva/ m.”; “Type/ 13247 [red label]”; “MCZ-ENT/ 00013247/ data matrix code”; “ LECTOTYPE / Tritoxa / incurva Loew / des. B.J. Sinclair 2020 [red label]” ( MCZ). GoogleMaps

Taxonomic notes. Loew based this species on an unspecified number of male and female specimens. A lectotype is here designated in order to fix the identity of the species.

Additional material examined. CANADA. Ontario: Beamsville [43°09′N 79°28′W], 23.viii.1977, R.G. Bennett (1♂, 1♀, DEBU) GoogleMaps ; Elgin Co., Newport Forest , ~ 3 km SW of Wardsville, 42°37′52″N 81°46′43″W, 30.vii.2009, S.A. Marshall (1♀, DEBU) GoogleMaps ; Essex Co., Windsor, Ojibway Prairie [42°15′N 83°05′W], 22.ix.2001, S. Paiero (1♂, DEBU) GoogleMaps ; same data except, 21.vii.2000, S.A. Marshall (1♂, DEBU) GoogleMaps ; same data except, 26–27.viii.2002, S. Paiero (1♂, DEBU) GoogleMaps ; Essex Co., Windsor [42°15′N 83°02′W], Spring Garden Road ANSI, 28.vii. 2005, M.D. Bergeron (1♂, DEBU) GoogleMaps ; Essex Co., Pelee Island [41°45′N 82°45′W], Stone Rd. Alvar, 1.x.2000, S.A. Marshall (1♀, DEBU) GoogleMaps ; Essex Co., Windsor, Broadway Pk [42°16′17″N 83°5′7″W], 13.ix.2005, S.M. Paiero (1♀, DEBU) GoogleMaps ; Harrow [42°02′N 82°55′W], 24.viii.1975, G.J. Umphrey (1♀, DEBU) GoogleMaps ; Jarvis [42°53′N 80°06′W], viii.1961, Taylor & Wood (2♂, CNC) GoogleMaps ; same data except, 15.x.1960 (1♂, CNC) GoogleMaps ; River Canard [42°06′N 83°05′W], 10.vii.1977, W.A. Attwater (4♂, 1♀, DEBU) GoogleMaps ; same data except, E.A. Innes (1♂, DEBU) GoogleMaps . Saskatchewan: Grasslands NP, West Black nr Frenchman River , grassland prairie, 49.149° -107.53°, 804 m, 27.viii.2012, A. Pawlowski, BIOUG03413 View Materials -D02 (1♂, barcoded, CBG) . USA. Alabama: Clay Co., Millerville [33°11′N 85°55′W],, H.G. Barwood (5♂, 1♀, USNM) GoogleMaps ; Cleburne Co., Mt Cheaha [33°29′N 85°48′W], 2400 ft, 23.v.1965, J.G. Chillcott (2♂, CNC) GoogleMaps . Arkansas: Lincoln Co., Gould [33°59′N 91°33′W], vii.1954, P.H. Thompson (1♂, USNM) GoogleMaps ; Knoxville, rest stop I-40 East , 35.3666°N 93.344°W, 17.v.2010, Biobus 2010, 10BBDIP-0310, 10BBDIP-0793 (1♂, 1♀, barcoded, CBG) GoogleMaps . Colorado: Boulder, Flagstaff Canyon [40°00′N 105°18′W], 5800 ft, 8.viii.1961, J. R. Stainer (1♀, CNC) GoogleMaps ; Estes Park [40°22′N 105°31′W], 14.viii.1949, R. R. Dreisbach & R. K. Schwab (1♂, CNC) GoogleMaps ; no locality or date, J.M. Aldrich (1♂, USNM) ; Florissant [38°56′N 105°17′W], 8.viii.1973, C.W. Sabrosky (1♀, USNM) GoogleMaps ; Hugo [39°8′N 103°28′W], 7.vii.1907, C.H. Marsh (1♂, USNM) GoogleMaps . Connecticut: Branford [41°16′N 72°47′W], 5.vii.1921, P. Garman (2♂, 1♀, 1?, USNM) GoogleMaps ; Meriden [41°32′N 72°47′W], 31.viii.1933, B.H. Walden (2♀, USNM) GoogleMaps ; Milford [41°13′N 73°03′W], Wheelers Farms, 23.vii.1936, M.B. Bishop (1♂, USNM) GoogleMaps ; Stratford [41°12′N 73°07′W], 6.ix.1933, B.H. Walden (2♂, 2♀, USNM) GoogleMaps . Georgia: Athens [33°57′N 83°23′W], ex Pinus taeda , 17.v.1965, H.O. Yates (1♂, 1♀, USNM) GoogleMaps ; Marietta [33°57′N 84°32′W], 20.v.1965, R. C. Froeschner (1♀, USNM) GoogleMaps ; Rockyford [32°39′N 81°49′W], 25.viii.1957, W. R. Richards (1♂, CNC) GoogleMaps . Illinois: Beverley Hill [s] [41°42.6′N 87°40.8′W], 15.vii.1903 (1♀, USNM) GoogleMaps ; Zeigler [37°53′59″N 89°3′12″W], 27.viii.1929, J. Karlovic (1♂, 2♀, USNM) GoogleMaps . Iowa: Ames [42°02′N 93°37′W], vii.1890, J.M. Aldrich (1♂, USNM) GoogleMaps ; Delaware Co., Robinson [42°20′N 91°34′W], 24.vii.1924, N.M. Bigelow (1♀, CNC) GoogleMaps ; Pleasant Valley [41°34′N 90°28′W], 5.vii.1928, G.S. Walley (1♂, CNC) GoogleMaps ; Lucas Co., Red Haw SP, 41°00′N, 93°16′W, 24.viii.1998, N.D. Penny (1♂, CAS) GoogleMaps ; Monroe Co., Tyrone Wildlife Area , 40°59′N, 92°56′W, 23.viii.1998, N.D. Penny (1♂, 1♀, CAS) GoogleMaps . Kansas: Labette Co., Oswego [37°10′N 95°6′W],, G.F. Hevel (1♂, 1♀, USNM) GoogleMaps ; same data except, 9.x.1963 (1♂, USNM) GoogleMaps . Kentucky: Fort Knox [37.92°N 85.96°W], 7.vii.1963, P.E. Adams (1♀, CSCA) GoogleMaps . Maryland: Prince Georges Co., Beltsville [39°2′N 76°55′W], 18.ix.1969, R. E. Holmes (1♂, 1♀, USNM) GoogleMaps ; same data except, 18.ix.1964, P.H. Arnaud (1♀, CAS) GoogleMaps ; Prince Georges Co., Patuxent Research Station [39.06°N 76.78°W], 24.viii.1986, N.E. Woodley (1♂, USNM) GoogleMaps . Mississippi: v.1920, F.M. Hull (1♂, CNC) ; Lafayette Co., v.–vi.1945, F.M. Hull (1♂, 1♀, CNC) ; same data except, 1–15.v.1949 (1♀, CNC) ; same data except, v.–vi.1960 (1♀, CNC) ; same data except, vi.1934 (2♂, 2♀, CNC) ; Oxford [34°21′N 89°31′W], 15.viii.1954, F.M. Hull (1♂, CNC) GoogleMaps ; State College , 5.x.1932, D. Shaw (1♂, USNM) . Missouri: Columbia [38.951°N 92.328°W], Malaise, 23.x.1968, F.D. Parker (1♂, USNM) GoogleMaps ; 25 mi. S St. Louis [38°37′N 90°11′W], 3.viii.1965, W. Hoele & J. Lovily (1♀, LEM) GoogleMaps . Montana: Petroleum Co., 1.5 mi S, 5 mi W Winnett [47°0′N 108°21′W], 30.vii.1969, C.B. Hewitt (1♀, USNM) GoogleMaps ; Roundup [46°26′54″N 108°32′34″W], 3.ix.1924, H.L. Seamans (2♂, 1♀, CNC) GoogleMaps . New Jersey: Hunterdon Co., Bulls Island SP [40°24′N 75°2′W], 27.vii.1974, A.S. Menke (1♀, CSCA) GoogleMaps ; Millington [40°40′38″N 74°31′04″W], 7.viii.1958, E.J. Hansens (1♂, 1♀, USNM) GoogleMaps ; Hopewell [40.389°N 74.763°W], Stoney Brook Millstone Watershed, Adventure Trail ,, J. Lento (1 ♀, DEBU) GoogleMaps ; Ramsey [41.059°N 74.145°W], 30.vii.1912, J. R. Malloch (1♂, 1♀, USNM) GoogleMaps . New York: no date or collector (1♀, USNM) ; 8.9.1890, illegible (1♂, USNM); (1♂, USNM) ; Staten Is. [40°34′N 74°8′W], 1923, A.H. Sturtevant (1♂, 1♀, USNM) GoogleMaps . North Carolina: Highlands [35°3′N 83°11′W], 3800 ft, 10.v.1957, J. R. Vockeroth (1♂, CNC) GoogleMaps ; Johnston Co. [35°31′N 78°22′W], 8.x.1961, D.L. Davies (2 ♀, DEBU) GoogleMaps . North Dakota: Beach [46°54′N 104°00′W], no date, C.N. Ainslie (1♀, CNC) GoogleMaps ; same data except, 28.viii.1923 (1♀, CNC) GoogleMaps . Ohio: Athens [39°19′N 82°5′W], 28.ix.1933, W.C. Stehr (1♀, USNM) GoogleMaps . Pennsylvania: Reading [40°20′N 75°55′W], 23.vii.1895, no collector (1♀, USNM) GoogleMaps . South Carolina: Aiken [33°32′N 81°43′W], 31.v.1957, H.F. Howden (1♂, CNC) GoogleMaps ; same data except, W.J. Brown (1♂, CNC) GoogleMaps ; Aiken , 24.viii.1957, W. R. Richards (1♀, CNC) ; Seneca [34°41′N 82°57′W], 20.viii.1957, L.A. Kelton (1?, CNC) GoogleMaps ; Spartanburg Co. [34°56′N 81°59′W], 12.ii.1961 (1♂, USNM) GoogleMaps ; York Co., Rock Hill Blackjacks Preserve [34°54′N 81°01′W], 25– 27.v.2001, A. Zayed (1♀, CNC) GoogleMaps . South Dakota: Brookings [44°18′N 96°47′W], 29.vii.1891, J.M. Aldrich (1♀, USNM) GoogleMaps ; same data except, 29.vii.1891 (1♂, 1♀, USNM) GoogleMaps ; Murdo [43°53′N 100°42′W], 19.viii.1963, C. V. Reichart (1♂, USNM) GoogleMaps . Tennessee: Memphis [35°07′N 89°58′W], 4/7 1927, F.M. Hull (1♀, CNC) GoogleMaps ; Morristown [36°12′N 83°17′W], 18.viii.1981, F. Liard (1♂, LEM) GoogleMaps . Texas: Paris [33°39′N 95°32′W], 6/10 1904 (1♀, USNM) GoogleMaps ; Travis Co., Austin [30°16′N 97°44′W], 2–7.v.1980, P.D. Hurd, Thelesperma filifolium (1♀, USNM) GoogleMaps . Utah: Salt Lake City [40°45′N 111°53′W], 4.vii.1951, F.C. Harmston (1♀, USNM) GoogleMaps . Wyoming: Larimie Co., Rte 80, Hillsdale [41°12′N 104°28′W], on sunflower, 29.vii.1974, PSB (1♀, CAS) GoogleMaps .

Diagnosis. Trixoxa incurva can be recognized by its rather broad, rounded wings, strongly arched subapical hyaline crossband and inner surstylus with 3–4 large prensisetae.

Redescription. Entirely reddish yellow to brownish, abdomen darker ( Fig. 2 View FIGURES 1–2 ). Head: ocellar triangle reddish-brown; frons reddish-yellow; silvery parafrontal microtrichose stripe narrow ( Fig. 3 View FIGURES 3–5 ), continuous with slightly broader microtrichose parafacial; gena reddish brown below narrowest part of lower eye margin; postocular microtrichia wider than parafrontal microtrichia in lateral view, extending from oral margin to middle of eye; face yellow to reddish yellow; supracervical setulae usually yellow. Antenna with postpedicel greyish dorsally, yellowish ventrally. Proboscis with palpus yellowish with apical half greyish. Thorax: reddish-yellow; scutum mostly thinly pruinescent with pair of whitish microtrichose vittae; lateral margin of scutum and postpronotal lobe broadly shiny; scutellum concolourous with scutum; mediotergite sometimes with faint stripe; pleura shiny, extreme posterior portion of anepisternum and katepisternum lightly clothed in whitish microtrichia when viewed obliquely; whitish microtrichia above fore coxa; 1 anepisternal seta. Wing ( Fig. 10 View FIGURES 6–13 ) broad, rounded apically, brown, especially along margins of crossbands, with some faded or paler regions; costal cell without narrow hyaline band at humeral break, with small white band at apex in line with discal hyaline crossband; often hyaline area from apical region of Sc to R 1; oblique subbasal hyaline crossband reaching mid-length to two-thirds length of cell dm; discal hyaline crossband oblique, arched, continuous from R 1, broader posteriorly, extending to near posterior distal corner of cell dm; subapical hyaline crossband broad, strongly arched, anterior end extending proximal to crossvein r-m; crossvein dm-m straight; anal lobe well-developed; calypter without white margin. Abdomen: black or brownish black, sometimes chestnut brown on sides of, or in centre of, tergites 1–2. Male terminalia ( Fig. 19 View FIGURES 18–19 ): inner surstylus with 3–4 thick prensisetae, distinctly separated, with middle prensiseta larger than others, inner margin straight; outer surstylus narrow, straight, longer than base with rounded apex; subepandrial sclerite with a few scattered setae. Cercus with long apicolateral setae; apical margin rounded and pointed. Phallus long, with some 4–5 loops.

Distribution. Tritoxa incurva is the most widespread species of this genus, known from Connecticut to Utah and Saskatchewan and southern Ontario to Texas ( Fig. 27 View FIGURES 27–29 ). Paiero et al. (2010) published the first Canadian record of this species (although earlier collection records are present in CNC and DEBU). The identification of the single female specimen from Wyoming listed above remains uncertain. Additional material is required to confirm the presence of this species in this state.

Remarks. Allen & Foote (1975) detailed the life history of T. incurva , including description of immature stages. Although T. incurva larvae may feed on commercial onions, its natural host plant is wild garlic, Allium canadense L., with the larvae found feeding on the bulbs. Courtship behaviour involves wing waving, “bubble blowing” and the expansion of an orange membrane from the mouthparts. They breed late in the season having one, occasionally two, generations per year. The eggs overwinter, hatching early the following spring ( Allen & Foote 1975). Paiero et al. (2010) classified T. incurva as a tallgrass prairie associated species.


Museum of Comparative Zoology


Departamento de Geologia, Universidad de Chile


Ontario Insect Collection, University of Guelph


Canadian National Collection of Insects, Arachnids, and Nematodes


Australian National Botanic Gardens, specimens pre-1993


Smithsonian Institution, National Museum of Natural History


California Academy of Sciences


California State Collection of Arthropods


Royal British Columbia Museum - Herbarium














Tritoxa incurva Loew

Sinclair, Bradley J., Macleod, Alyssa M. & Wheeler, Terry A. 2021

Tritoxa incurva

Loew, H. 1873: 104