Arganthomyza bivittata, Rohacek & Barber, 2013

Roháček, Jindřich & Barber, Kevin N., 2013, A worldwide review of the genus Arganthomyza Roháček, with revision of the Nearctic species (Diptera: Anthomyzidae), Zootaxa 3604 (1), pp. 1-72 : 21-25

Arganthomyza bivittata sp. n.

Figures 5, 6 , 82–99 , 168

Type material: Holotype ♂ labelled: “CAN: ON: SSMarie, Baseline Rd., 22.vi.2005, KN Barber, sweeps, Aster [ Doellingeria ], Rubus , Equisetum , Carex , ferns, under aspen, 46°31.40’N 84°24.40’W ” and “ HOLOTYPUS ♂, Arganthomyza bivittata sp.n., J. Roháček & K. N. Barber det. 2011” [red label] ( DEBU, intact). Paratypes: CANADA: Alberta: ~1.2 km S Cadomin, entrance to Whitehorse Wildland P. Pk., 53°00.70’N 117°20.05’W, sweeps, Bromus inermis , Hedysarum boreale , 23.vii.2008, 1♀, K. N. Barber leg. ( DEBU); Dunvegan, N side Peace River, pan traps in grasses, S. Boucher leg., 19–28.vi.1995, 8♂ 11♀ ( LEMQ 0040018-23, -25-28, -31, -37-40, -49, -50, 51, -82), 28.vi.-11.vii.1995, 25♂ 13♀ (1♀ genit. prep.) ( LEMQ 0040032-33, -46-48, -52-55, -56-61, -64-75, - 77-81, -83-86, -89, -91), 11-25.vii.1995, 7♂ 3♀ ( LEMQ 0040024, -29, -41-45, -62, -63, -92), 25.vii.-1.viii.1995, 3♂ 1♀ (1♂ genit. prep.) ( LEMQ 0040034, -35, -36, -90); Dunvegan, N shore of Peace River, sweep grasses along agricultural field, 14.vii.1997, 1♂, T. A. Wheeler leg. ( LEMQ 0040087); Edmonton, 7.viii.1945, 1♂, E. H. Strickland leg. ( USNM); [Fort] McMurray, 30.vii.1953, 1♂, 10.vii.1953, 1♂ 2♀ (1♂ genit. prep.), 4.viii.1953, 1♂, 8.viii.1953, 4♂ 1♀, G. E. Ball leg. ( CNCI). British Columbia: Hazelton, 30.vii.1920, 1♀, C. M. Barbeau leg. ( CNCI); Kinbasket Lake, BC Hydro drawdown study, 12MCOT15, Malaise trap, 17–18.vii.2009, 1♂, Beauchesne & Assoc Ltd. leg. ( RBCM); Terrace, 13.vii.1960, 1♀, 2.viii.1960, 1♂ 2♀ (1♂ 1♀ genit. prep.), W. R. Richards leg. ( CNCI). Manitoba: 5 mi N Minnedosa, 8.vii.1958, 1♀, R. L. Hurley leg. ( CNCI). Nova Scotia: Sable Is[land] west end, 5.vii.1967, 2♂, 11.vii.1967, 1♂ D. M. Wood leg. ( CNCI, 1♂ headless & genit. prep.); Truro, 14.vii.1983, 2♂ 1♀ J. R. Vockeroth leg. ( CNCI). Ontario: Marmora, swept from Urticacous [sic. Urticaceae ?], 25.viii.1952, 3♂ 2♀, J. F. McAlpine leg. ( CNCI); Ottawa, 18.vii.1946, 2♂ 10♀, A. Brooks leg., 12.viii.1946, 1♀, A. R. Brooks leg., 19.vii.1946, 4♂ 6♀ (1♂ 2♀ genit. prep.), G. E. Shewell leg. (all CNCI); Ottawa, 22.vi.1963, 1♀, 6.vii.1963, 3♂ 3♀, 13.vii.1963, 1♂ 2♀, 20.vii.1963, 1♀; Ottawa, Black Rapids, 28.vi.1959, 3♂, all J. R. Vockeroth leg. (all CNCI); Fergus, Grand R. floodplain, 43°41.3’N 80°23.4’W, sweeps/ pooter Bromus inermis , 17.vii.1997, 2♀; Guelph, 4.vii.1979, 1♂; ~ 8 km NE Heyden, Hwy.552 @ Bellevue Valley Rd., 46°42.85’N 84°17.12’W, sweeps, ferns, sedges, Rubus , Impatiens , under Fraxinus , 23.vi.2007, 1♀, all K. N. Barber leg. (all DEBU); S[ault] S[te.] Marie, S of Algoma U[niversity] College, 46°29.9’N 84°17.2’W, sweeps, Onoclea sensibilis , 22.vi.1998, 1♀; as above but sweeps, Impatiens under Populus / Betula , 13.vii.1998, 1♀; as above but sweeps, graminoids under Populus / Betula , 11.vii.1997, 1♂, 23.vii.1997, 1♂ 1♀, all K. N. Barber leg. (all DEBU); S[ault] S[te.] Marie, Baseline Rd., 46°31.40’N 84°24.40’W, sweeps, Aster [ Doellingeria ], Rubus , Equisetum , Carex , ferns, under aspen, 22.vi.2005, 5♂ 5♀ (1♂ 1♀ genit. prep.), 25.vi.2005, 6♂ 2♀ (1♂ genit. prep., all DEBU), 26.vi.2005, 5♂ 5♀, (2♂ 2♀ SMOC, 3♂ 3♀ DEBU), 8.vii.2005, 3♂ 1♀, 10.vii.2005, 5♂ 4♀ (1♀ genit. prep.), 14.vii.2005, 1♀, 16.vii.2005, 1♂ 2♀, 18.vii.2005, 3♂ (1♂ wing removed), 22.vii.2005, 1♂ 1♀, 27.vii.2005, 1♂, 6.viii.2005, 1♂ 2♀, 17.viii.2005, 2♂, 28.viii.2011, 1♀, 5.ix.2011, 1♂, 27.vii.2012, 1♀, 29.vii.2012, 6♂ 1♀, K. N. Barber leg. ( DEBU); as above but 23.viii.2011, 2♂ 2♀, K. N. Barber leg. ( SMOC, 1♂ with abdomen used for non-destructive extraction of DNA); as above but sweeps, mostly Carex in aspen clearing, 25.vi.2005, 1♂, 16.vii.2005, 3♂ 1♀; as above but sweeps, Carex gynandra , 8.vii.2006, 1♂, all K. N. Barber leg. (all DEBU); as above but sweeps, mostly ferns under aspen, 27.vii.2012, 8♂ 10♀ (2♂ 2♀ each AMNH, CASC, EMUS, 2♂ 4♀ DEBU), 28.vii.2012, 15♂ 12♀ (2♂ 2♀ USNM, 7♂ 7♀ SMOC, 6♂ 3♀ DEBU), 29.vii.2012, 4♂ 8♀ (2♂ 2♀ CNCI, 2♂ 6♀ DEBU), 25.viii.2012, 1♂ 2♀ ( DEBU), all K. N. Barber leg.; as above but sweeping Aster [ Doellingeria ], Rubus , Equisetum , Carex , Clematis , ferns under aspen ( Populus ), 7.vii.2010, 1♂, J. Roháček leg. ( SMOC); S[ault] S[te.] Marie, Birchwood Pk., 46°30.7’N 84°15.6’W, sweeps, mostly Aralia , fern, Impatiens , dewberry, grass under Betula / Acer , 30.viii.1997, 1♂ 3♀; as above but sweeps, mostly fern, Aralia , Impatiens , dewberry, grass under Betula / Acer , 30.viii.1997, 1♂; as above but sweeps, trailside Impatiens , fern, raspberry, grass under Betula / Acer , 30.viii.1997, 1♂ 1♀, 1.ix.1997, 4♂ 3♀ (1♂ genit. prep.), 4.ix.1997, 1♂ 1♀, 18.ix.1997, 2♀; as above but sweeps, graminoids by trail, 22.ix.1997, 1♀; as above but sweeps, including Impatiens under Betula / Acer , 20.vi.1998, 1♀, all K. N. Barber leg. (all DEBU); S[ault] S[te.] Marie, Bristol Pl[ace] Pk., 46°30.8’N 84°16.6’W, sweeps, Carex sp. under Populus / Betula , 9.viii.1997, 1♀; as above but 46°30.77’N 84°16.66’W, sweeps, Impatiens , Clematis , Equisetum , Rubus , ferns, Phalaris , 4.vii.2008, 1♂; S[ault] S[te.] Marie, Centennial Dr. Pk., 46°30.2’N 84°16.0’W, sweeps, low veg. under Populus / Betula , 1.ix.1997, 2♂; S[ault] S[te.] Marie, Ft. Creek Cons[ervation] Area, 46°32.5’N 84°20.8’W, sweeps, Impatiens , sedge, fern, 8.vii.1998, 1♀ (genit. prep.); S[ault] S[te.] Marie, Wishart Pk., 46°33.86’N 84°17.57’W, sweeps, graminoids/ ferns under canopy, 23.vii.2005, 1♂, all K. N. Barber leg. (all DEBU); Icewater Creek WS [watershed], [~14.7 km N Searchmont], 46°53.7’N 84°03.4’W, sweeps, Thalictrum , sedge, fern, riparian mixed forest, 7.vii.1998, 1♂ 4♀; as above but pitfalls, moist depression in mixed forest, Thalictrum / Eupatorium [ Eutrochium ], 24.vii-6.viii.1998, 1♀, 6–24.viii.1998, 1♀, all K. N. Barber leg. (all DEBU); Serpent River, Hwy. 17 picnic area, 46°12.60’N 82°30.83’W, sweeps, Clintonia , Smilacina [ Maianthemum ], ferns, Trientalis , under Acer / Betula , 5.ix.2009, 1♂; Short Hills P[rovincial] P[ark], Terrace Ck. Trail east loop, 43°05.8’N 79°16.1’W, mostly Carex / Impatiens in mixed hardwood, sweeps, 17.vii.2002, 2♂ (1♂ genit. prep.) all K. N. Barber leg. (all DEBU). Quebec: Breckenridge, 14.vii.1959, 1♀, C. H. Mann leg.; Hull, 14.vi.1959, 1♂, J. R. Vockeroth leg.; Rupert House, 8.viii.1949, 1♀, E. J. LeRoux leg. (all CNCI). Saskatchewan: Beaver Creek Cons[ervation] Area, ~ 13 km S Saskatoon, 51°58.6’N 106°43.0’W, sweeps, mostly grasses under Betula / Populus , 12.vii.1999, 1♀, K. N. Barber leg. ( DEBU); Beaver River, 5 mi S Goodsoil, 6.vii.1985, 2♂ 1♀, D. W. Webb leg. ( INHS 40,216–218, 1♂ genit. prep.). UNITED STATES: Michigan: Emmet Co., Carp L., 16.vii.1988, 1♀, C. W. Sabrosky leg. ( USNM, headless).

Other material not designated as paratypes (damaged):

CANADA: Alberta: Dunvegan, N side Peace River , pan traps in grasses, 28.vi.–11.vii.1995, 1♂ 2♀, S. Boucher leg. ( LEMQ 0040030 , -76, -88, 1♂ missing head & abdomen, 2♀ missing abdomen) . British Columbia: Vernon , 22.vii.1931 [37?], 1♀, D. B. Waddell leg. ( CNCI, abdomen missing); Vernon, 4.viii.1932, 1♀, C. Bigland leg. ( RBCM, legs, wing, abdomen missing) .

Material of Arganthomyza cf. bivittata (questionable status):

CANADA: Nova Scotia: Lockeport , 25.vii.1958, 1♀, J. R. Vockeroth leg. ( CNCI, genit. prep.) .

Etymology: The species is named “bivittata” for the pair of dark longitudinal vittae present (rarely missing) on the mesonotum. The name was first used by G. E. Shewell for this new species in CNCI long ago.

Description: M a l e. Total body length 2.12–2.94 mm; general colour largely yellow, with some brown pattern on head, thorax and abdomen ( Figs 5, 6 ), sparsely light grey microtomentose and relatively shining. Head bicolourous, yellow to white and (posteriorly only) dark brown ( Fig. 6 ), slightly higher than long, rounded anteriorly in profile. Occiput dorsomedially concave, largely dark brown, only lateroventrally ochreous to yellow and with a pair of short yellow spots or stripes behind ocellar triangle, sparsely grey microtomentose but shining. Frons dull and yellow, only ocellar triangle brown to dark brown and shining. Frontal triangle dark yellow, very sparsely microtomentose and shining, with acutely projecting anterior corner. Orbit whitish yellow and entirely silvery white microtomentose; a silvery white microtomentose stripe between posterior part of orbit and frontal triangle broad and anteriorly connected with similarly microtomentose orbit, posteriorly reaching to vti and pvt. Rest of frons brightly yellow, without microtomentum but dull. Frontal triangle short and very narrow, reaching only half of frons. Frontal lunule pale yellow, small. Face narrow, medially weakly sclerotized and concave, yellowish white, whitish microtomentose and dull; border line separating it from parafacialia ochreous-yellow. Parafacialia and gena almost white and densely silvery white microtomentose; ventral marginal stripe of gena ochreous and narrowly so posteriorly. Postgena whitish yellow, posterodorsally confluent with yellow to ochreous lateroventral part of occiput. Mouthparts dirty yellowish white, only (small and narrow) clypeus darker yellow. Cephalic chaetotaxy: pvt fine but unusually long (up to as long as anterior ors), with apices strongly crossed; vti and oc subequal, very long, longest of cephalic setae; oc proclinate, slightly divergent; vte and posterior ors strong, subequal but shorter than vti; 2 ors, anterior variable, slightly to distinctly shorter than posterior; 1–2 microsetula(e) in front of the anterior ors; 2–4 pairs of medial microsetulae in front of frontal triangle; 1 inclinate short seta behind vte; postocular setulae relatively long and sparse (6–7), in single row; postgena with several setulae and 2 (1 longer) pale posteroventral setae; 1 relatively long weak vi (usually longer but finer than anterior ors); subvibrissa distinct, up to two-thirds of vi length but finer and at least twice longer than peristomal setulae; 6–8 fine peristomal setulae. Palpus slender, dirty whitish, with 1 fine dark ventral preapical seta (shorter and thinner than subvibrissa) and 6–8 paler ventral setulae. Eye large, suboval, with longest diameter slightly oblique, about 1.2 times as long as shortest. Gena with shortest height about 0.10 times as long as shortest eye diameter. Antenna with scape and pedicel yellow; 1st flagellomere yellowish white, with short white pilosity including cilia on anterior margin. Arista brown, with thickened pale brown basal segment, 1.9 times as long as antenna, with cilia shorter than those on apex of 1st flagellomere.

Thorax about as wide as head, largely yellow to pale yellow but mesonotum with brown or pale brown longitudinal vittae laterally to dc lines ( Fig. 6 ) typically continuing also on sides of scutellum and reaching to apical sc; sometimes these vittae can be faded or completely missing. Mesonotum relatively shining despite sparse pale grey microtomentum. Humeral (postpronotal) and notopleural areas usually yellowish white. Pleural part of thorax unicolourous pale yellow ( Fig. 5 ) or its dorsal marginal part narrowly darkened (up to pale brown). Mesonotal microsetae less reduced than in relatives; macrosetae very long. Thoracic chaetotaxy: 1 hu (slightly longer than posterior npl); 2 npl (anterior long, slightly shorter than prs, posterior short); 1 very long prs (subequal to anterior dc); 1 very long sa (as long as prs); 1 pa (long but shorter than sa); 2 very long postsutural dc (posterior longest of thoracic setae, anterior shorter but also long, as long as prs) and 5–6 dc microsetae in front of them; ac microsetae in 2 long medial rows reaching from level of prs almost to level of posterior dc; a long row of microsetae also between prs and dc lines and several microsetae in front of prs; 2 sc, the short laterobasal often longer than hu, apical very long and robust, almost as long as posterior dc; scutellum otherwise with a variable set of microsetae: regularly 1–2 pairs between apical sc, sometimes 1–2 pairs on disc and 1 marginal between laterobasal and apical sc; 1 very fine but distinct ppl; 2 long stpl, anterior shorter and weaker, posterior almost as long as prs, 1 setula in front of anterior stpl and a number (9–12) of upcurved setulae below them; ventral part of sternopleuron with 4–5 longer setae. Scutellum rounded triangular, slightly convex dorsally. Legs pale yellow, coxae and bases of femora whitish, only distal half to two-thirds of apical tarsal segments blackish brown and contrasting with rest of tarsi. f 1 with ctenidial spine moderate, slightly to distinctly longer than maximum width of t 1 and with usual row of long posteroventral setae. f 3 with a long row of posteroventral setae, 7–8 of which in distal two-fifths shortened and thickened (5 usually markedly thicker); t 2 with relatively short ventroapical seta; all basitarsi proximoventrally with 1 or 2 longer pale hair-like setulae. f 2, t 1 and t 3 simply setulose. Claws relatively long as in other Arganthomyza species. Wing ( Fig. 168 ) moderately narrow, with pale ochreous veins and unicolourous hyaline membrane. C with distinct small spinulae between apices of R 1 and R 2+3. R 2+3 long, bent parallel to C with apex very slightly upcurved to C; R 4+5 very slightly bent (recurved) and terminally almost parallel to M. Discal (dm) cell moderate, with r-m situated distinctly in front of the middle of dm cell. Apical portion of CuA 1 usually longer than dm-cu and almost reaching wing margin; A 1 short, ending far from it. Alula small, moderately broad (less than in A. socculata ). Wing measurements: length 1.96–2.92 mm, width 0.67–1.01 mm, Cs 3: Cs 4 = 1.32–1.53, rm\dm-cu: dm-cu = 2.20–3.36. Haltere with yellow stem and paler, yellowish white knob.

Abdomen with preabdominal terga and sterna yellow to pale yellow ( Fig. 5 ), sparsely microtomentose and shining. Sometimes preabdominal terga (or some of them) can appear to be brownish laterally or posterolaterally, darkened by internal (reddish brown when alive) tissues. T2–T5 and S2–S5 with denser and longer setae than those of all relatives. T1 and T2 dorsally separate, only laterally fused. T3–T5 subequal, broad, bent onto ventral side of abdomen. Preabdominal sterna relatively narrow and becoming wider posteriorly; S1 short and transverse, bare and with darker posterior marginal stripe; S2–S4 slightly longer than wide or S4 as long as wide; S5 largest, wider than long, distinctly transverse, with slightly emarginate posterior margin, shortest medially. T6 short, transversely band-like, bare, pale yellow, submedially desclerotized and unpigmented. S6–S8 dorsally fused together. S6 (ventrally band-like, slightly shorter and distinctly paler than S7) and S7 (pale brown) strongly asymmetrical, both with more sclerotized and darker anterior margin and each with 2 short setae; S8 long (longer than epandrium), pale brown to brown, with a number of setae in posterior half and shining despite sparse pale grey microtomentum as is (darker) epandrium.

Genitalia generally resembling those of A. acuticuspis and A. duplex . Epandrium ( Figs 82, 83 ) brown, relatively long (as in A. duplex ) and almost hemispherical but distinctly narrower than in both above relatives, with relatively long setae, 2 dorsolateral setae longest; anal fissure (dorsally) slightly wider than in relatives, with small lateral notch (cf. Fig. 82 ). Cercus somewhat shorter than that of A. acuticuspis and A. duplex , pale-pigmented and finely setose, with 2–3 apical and subapical setae longer than others. Medandrium ( Fig. 83 ) relatively high, dorsally narrower than that of A. duplex , medioventrally broadly and rather deeply emarginate, dorsally narrowed and with small but acutely projecting dorsolateral corners and distinct posteromedial keel. Gonostylus ( Figs 82–84 ) yellow, flat, in sublateral view subtriangular and hence most similar to that of A. acuticuspis but broader, with less acute tip, and more bent medially (cf. Fig. 83 ); its outer side micropubescent except for narrow anterior and dorsal margins and small apical area ( Fig. 84 ); macrosetae on inner side relatively long. Hypandrium ( Figs 85, 86 ) moderately robust, with larger terminal pale part than in both closest relatives. Transandrium ( Fig. 87 ) most resembling that of A. duplex including seemingly forked (mediodistally membranous) caudal process. Pregonite ( Figs 85, 86 ) low and its posterior darker lobe separated by narrow incision and distinctly projecting, with 3 (2 longer) posterior setae on its apex and 3 (1 long, 1 shorter and 1 small) anterior setae, all inserted on its inner side. Postgonite ( Figs 85, 86 ) slender but distally widened machete-like, flat and pale-pigmented; its narrow proximal part darker and with 1 anterior setula near middle and a few grain-like sensilla on outer side. Basal membrane ( Figs 85–87 ) with dense but very pale, flat, spine-like excrescences. Aedeagal part of folding apparatus with dorsal area covered by small granulose excrescences, posteroventrally with fine, flat and pale transverse tubercles and anteriorly with some fine striae. Connecting sclerite very slender, largely membranous, of indistinct structure ( Fig. 89 ). Phallapodeme as in related species, with basal part deeply forked, fulcrum resembling that of A. duplex but bicuspidate apex less projecting. Aedeagus with short phallophore ( Fig. 89 ) and large distiphallus basally bearing internal sclerites. Ventral sclerite connecting phallophore with ventrobasal sclerite of distiphallus rounded. Saccus of distiphallus distally with hyaline hemispherical tubercles larger than in relatives. Filum robust proximally but narrower than in both A. acuticuspis and A. duplex and formed by 2 closely attached and partly fused band-like sclerites (one markedly narrower than other) terminating in submembranous, widened, flat, fissate and curved apex ( Fig. 88 ), being partly finely striated but lacking microspinulae. Ejacapodeme with relatively short and simple digitiform projection ( Fig. 89 ).

F e m a l e. Similar to male unless mentioned otherwise. Total body length 2.77–3.73 mm. Occiput with paired yellow medial stripes usually longer, ventrally tapered and reaching to occipital foramen. First antennal flagellomere darker yellow and on inner side often with a darker (ochreous) spot below base of arista. Dark vittae on mesonotum (and scutellum) more often reduced (lightened) or absent. f 1 with ctenidial spine slightly shorter, about as long as or slightly longer than maximum width of t 1. f 3 posteroventrally simply setulose. Wing measurements: length 2.77–3.45 mm, width 0.93–1.19 mm, Cs 3: Cs 4 = 1.32–1.59, rm\dm-cu: dm-cu = 2.09–2.95. Abdomen with preabdominal terga shorter and more transverse, all pale yellow but they can sometimes (more often than in males) appear reddish to brown laterally or in posterolateral corners. This darkening is caused by striking reddish purple internal tissues invariably visible in living specimens through pleural abdominal membranes. Similar but less striking markings also occur in females of A. carbo sp. n. and A. duplex sp. n. (see female of the latter in Fig. 100 ). T1 distinctly shorter than T2. T3 and T4 of the same length, T5 usually slightly longer than T4. T2–T5 with relatively dense and long setae. Preabdominal sterna pale yellow, slightly wider than in male despite larger pleural membrane. S1 short, bare, transverse and as wide as S2, with usual dark posterior transverse stripe; S2–S5 becoming wider posteriorly, all slightly to distinctly transverse and finely densely setose. S5 largest, widest posteriorly (but narrower than the slightly darker S6).

Postabdomen ( Figs 90–92 ) of medium length, at 6th segment wider than in A. acuticuspis and A. duplex , distally tapered. T6 large, wide, more densely setose and lighter than that of both above species. S6 relatively large, almost as broad as T7+S7 anteriorly, somewhat darker yellow than preabdominal sterna, with long fine setae at posterior and lateral margins. T7 and S7 completely fused to form ring-shaped tergosternum T7+S7 being dorsally shorter, darkpigmented only posterolaterally ( Figs 90, 92 ) but with posteromedial narrow pale interruption; ventral part of T7+S7 longer ( Fig. 91 ), largely pale yellow (except for lateral parts) but with long, dark, finely sinuate transverse ledge-like band, spiracles situated posterior to its lateral ends (contrasting with its two nearest relatives), with distinct (long) sparse micropubescence and long setae (more numerous than in relatives) at posterior margin. Membrane of 8th segment very finely micropubescent. T8 wider than in both A. acuticuspis and A. duplex , about as long as wide, anteriorly rounded, posteriorly almost straight, pale-pigmented and with long micropubescence. S8 markedly shorter and slightly wider than T8, formed by 2 finely setose sclerites, both posterodorsally recurved and invaginated inside 8th segment (see Fig. 93 ). Genital chamber medium broad but rather long ( Fig. 93 ), distally simply membranous; the proximal internal sclerotization formed by usual 1 pair of flat crooked (relatively pale) sclerites and 1 narrow, flattened and very pale-pigmented annular sclerite ( Figs 98, 99 ) being distinctly longer than in both A. acuticuspis and A. duplex . Ventral receptacle ( Fig. 95 ) elongate, slender, similar to that of above species but its proximal part wider, middle part curved and distinctly ringed, and terminal part shorter, curved and apex twisted worm-like ( Fig. 96 ). Accessory gland hyaline, irregularly vesiculate, on relatively slightly dilated duct. Spermathecae (1+1) broadly ovoid ( Figs 94, 97 ), both subequal in size, with dark transversely striated (striae usually interrupted) surface except for very basal part carrying a few (4–5) short, blunt and curved spines on bulges around duct insertion; duct short ( Fig. 93 ), with pale, hardly discernible cervix ( Fig. 97 ). T10 small, slightly transverse ( Fig. 90 ; longer than in relatives), darker pigmented only laterally, with some micropubescence and 1 pair of very long medial setae. S10 pale, larger than T10, short pentagonal ( Fig. 91 ) and micropubescent in posterior two-thirds. Cercus pale-pigmented, moderate in length and width, with fine setae, dorsopreapical and apical longest ( Fig. 93 ).

Discussion: Arganthomyza bivittata sp. n. belongs to the A. duplex group (see discussion under A. duplex sp. n. for more detail) and is most closely allied to A. duplex sp. n. –synapomorphies: female S2–S6 pale-pigmented (character 09); gonostylus with apex bent medially (character 11, cf. cladogram in Fig. 173 ). The shape of the gonostylus of this species is plesiomorphic, resembling in outline that of A. acuticuspis sp. n. and hence distinctly different from that of A. duplex sp. n., which has a modified gonostylus. Arganthomyza bivittata sp. n. can be easily distinguished from both close relatives and also from all other congeners by the colouration of the body, largely yellow (mesonotum with only a pair of narrow longitudinal brown vittae which can sometimes be absent, particularly in females; abdomen with yellow preabdominal terga and sterna), unusually long pvt setae, long medial rows of ac microsetae, uniquely setose scutellum with several microsetulae in addition to 2 usual pairs of long sc setae, and densely setose abdominal sclerites. Further diagnostic characters can be found in the male genitalia (gonostylus, filum of distiphallus) and female postabdomen (tergosternum T7+S7, spermathecae, internal sclerites of female genital chamber), see in the description and key above.

An unusually dark female specimen was found (listed separately as A. sp. cf. bivittata above) which possibly represents an extremely darkened form of A. bivittata sp. n. It differs from typical specimens of the latter by having the occiput also medially brown, the mesonotum with brown vittae widened to cover large area between dc lines and prs, sa and pa setae, the scutellum brown except narrow medial area and the pleural part of the thorax with a broad dorsal pale brown band. Also the abdominal terga are distinctly darker (visible in cleared abdomen) in this specimen, with T1+2 to T5 pale brown and T6 brown. However, because there seems to be also slight differences in the shape of the spermathecae (almost spherical) and T8 (more widened posteriorly), we cannot associate this specimen with A. bivittata with certainty, so its identification must wait for a similarly dark male to be found.

Biology: The habitat of this species can be generally described as mesic mixed or deciduous forest with relatively dense undergrowth of various components in Ontario (see Biology under A. duplex sp. n. for list of sites with three cooccurring species of Arganthomyza ). In the type locality the following plants can be found: Aster [ Doellingeria ], Clematis , Equisetum , Rubus , Carex , and ferns. Other collection sites in Ontario have included Clintonia , Impatiens , Maianthemum , Onoclea , Thalictrum , Trientalis , Carex , grasses and Urticaceae (?). It is still not clear which components of this undergrowth are being used by the larvae. This habitat can be contrasted with some of the western Canada collection sites where open areas dominated by grasses yielded specimens (Dunvegan and Cadomin, Alberta). Adults have been collected from 14 June (Hull, Quebec) to 22 September (Sault Ste. Marie, Ontario).

Distribution: Transcontinental in Canada from British Columbia to Nova Scotia (Alberta, British Columbia, Manitoba, Ontario, Nova Scotia, Quebec, Saskatchewan) with a single record from the United States (Carp Lake, Michigan).

Figures

FIGURE 173. One of two most parsimonious trees (L = 42 steps, CI = 0.80, RI = 0.81) chosen to represent the phylogeny of Arganthomyza species. Ambiguous characters (08, 13, 14, 18, 21, 29) are optimized using the fast (ACCTRAN) method. Full circles = non-homoplasious character states, empty circles = homoplasious character states. Numbers above branches agree with character numbering, those below branches indicate apomorphic (1, 2, 3) or plesiomorphic (0) states of characters. E PA = East Palaearctic, HO = Holarctic, NA = Nearctic, OR = Oriental, PA = Palaearctic.

FIGURES 1–6. General body appearance of Arganthomyza species, lateral (1–5) and dorsal (6, head and thorax only). 1—A. acuticuspis sp. n. (male holotype). 2—A. carbo sp. n. (male holotype). 3—A. duplex sp. n. (male holotype). 4—A. disjuncta sp. n. (female holotype). 5, 6—A. bivittata sp. n. (male holotype).

FIGURES 82–84. Arganthomyza bivittata sp. n. (male paratype, Canada: Ontario). 82—genitalia, lateral. 83—external genitalia, caudal. 84—gonostylus, lateroventral (widest extension). Scales: 0.1 mm. For abbreviations see text.

FIGURES 85–89. Arganthomyza bivittata sp. n. (male paratype, Canada: Ontario). 85—hypandrial complex, ventral. 86—ditto, lateral. 87—transandrium, caudal. 88—apex of filum of distiphallus, subventral (widest extension). 89—aedeagal complex, lateral. Scales: Fig. 88 = 0.05 mm, others = 0.1 mm. For abbreviations see text.

FIGURES 90–92. Arganthomyza bivittata sp. n. (female paratype, Canada: Ontario). 90—postabdomen, dorsal. 91—ditto, ventral. 92—ditto, lateral. Scale: 0.2 mm. For abbreviations see text.

FIGURES 93–99. Arganthomyza bivittata sp. n. (female paratype, Canada: Ontario). 93—apex of postabdomen and female genital chamber, lateral. 94—spermatheca. 95, 96—ventral receptacle, whole lateral (95), apex ventral (96). 97—spermatheca. 98—internal sclerites, lateral. 99—ditto, ventral. Scales: Fig. 93 = 0.1 mm, others = 0.05 mm. For abbreviations see text.

FIGURES 166–169. Wings of Arganthomyza species. 166—A. carbo sp. n. (male paratype, Canada: Ontario). 167—A. acuticuspis sp. n. (male paratype, USA: New Mexico). 168—A. bivittata sp. n. (male paratype, Canada: Ontario). 169—A. duplex sp. n. (male paratype, Canada: Ontario). Scale: 0.5 mm.

FIGURES 100–105. Habitus and habitats of Arganthomyza species. 100–101. A. duplex sp. n. alive (Dubreuilville, Ontario, Canada), mating pair laterally (100), female dorsolaterally (101). 102, 103—habitat of A. duplex and A. carbo, fern-dominated undergowth of mixed forest at Dubreuilville with K. N. Barber collecting (102), with detail (103). 104, 105—habitat of A. disjuncta sp. n., montane meadow; detail with Bromus inermis at Cadomin and general view (105) near Little Highwood Pass (both Alberta, Canada). Photo by J. Roháček (100–103) and K. N. Barber (104, 105).