Arganthomyza disjuncta, 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 : 34-38

Arganthomyza disjuncta sp. n.

Figures 4 , 121–136 , 170

Type material: Holotype ♀ labelled: “CAN: AB: ~1.2kmS Cadomin, entrance to Whitehorse Wildland PPk., 23.vii.2008, KNBarber, sweeps, Bromus inermis , Hedysarum boreale , 53°00.70’N 117°20.05’W ” and “ HOLOTYPUS ♀, Arganthomyza disjuncta sp.n., J. Roháček & K. N. Barber det. 2011” [red label] ( DEBU, intact) . Paratypes: CANADA: Alberta: Banff, m.14 Banff-Jasper Hwy. , 3.viii.1955, 1♀, R. Coyles leg. ( CNCI) ; Banff N. P., Mt. Eisenhower , 27.vii.1967, 1♂, B. A. Foote leg. ( USNM, genit. prep.) ; Cadomin, base of Prospect Mt. , mouse runs in grass, 18.vii.1987, 3♀, S. A. Marshall leg. ( DEBU, 1♀ genit. prep. missing both wings) ; ~ 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, 12♂ 7♀, K. N. Barber leg. (8♂ 5♀ DEBU, 1♂ wing removed, 3♂ 1♀ genit. prep., 4♂ 2♀ SMOC, 1♂ genit. prep.) ; ~ 3.7 km NNE Cadomin, Hwy. #40, 53°03.84’N 117°17.82’W, sweeps, roadside Bromus inermis , 23.vii.2008, 1♂, K. N. Barber leg. ( DEBU) ; Dunvegan , 55°55.39’N 118°35.74’W, sweep south facing grass slope at dusk, 19.vii.2003, 1♂, S. Boucher leg. ( LEMQ 0040625 ) ; Dunvegan , 55°55.25’N 118°35.40’W, sweep base of south facing grass slope, 20.vii.2003, 1♀ ( LEMQ 0040624 ) ; Dunvegan, N shore of Peace River , sweep grasses at edge of agricultural field, 13.vii.1997, 1♀, both T. A. Wheeler leg. ( LEMQ) ; ~ 26 km NW Highwood House, Mt. Lipsett pulloff, 50°33.26’N 114°57.27’W, sweeps, Bromus inermis , Leymus innovatus , 25.vii.2008, 19♂ 4♀ (3♂ 2♀ genit. prep.) ; Elbow-Sheep Wildland Pk., ~ 26 km NW Highwood House, 50°33.26’N 114°57.27’W, Mt. Lipsett day use, sweeps, various grasses, 14.vii.2011, 1♀ ( DEBU 01502569 ) ; Elbow-Sheep Wildland Pk., ~22.5 km NW Highwood House , 50°31.38’N 114°53.17’W, 14.vii.2011, sweeps, Carex sp. (large), 5♂ 3♀ ( DEBU 01502585-92 ) ; as above but sweeps, grasses incl. Poa compressa , 12♂ 3♀ ( DEBU 01502645-59 ) ; Peter Lougheed, P. Pk. , 0.5 km W Little Highwood Pass, 50°38.55’N 115°02.94’W, sweeps, roadside grasses incl. Bromus inermis , 14.vii.2011, 1♀ ( DEBU 01502567 ) , 16.vii.2011, 5♂ 7♀ ( DEBU 01502752-63 ) ; ~ 20 km SSE Robb, Hwy. #40, Lovett River PRA [Provincial Recreational Area], 53°03.89’N 116°49.02’W, sweeps, streamside, mostly grasses, 23.vii.2008, 3♂ 4♀, all K. N. Barber leg. (all DEBU) . British Columbia: Atlin , 2200’, 4.vi.1955, 1♀, 7.vii.1955, 1♀, B. A. Gibbard leg., 6.vii.1955, 1♂, H. J. Huckel leg. ( CNCI) ; S of Atlin, Warm Springs , 2.vi.1997, sweep vegetation at warm stream margin, 1♂ 1♀, T. A. Wheeler leg. ; as above but sweep grasses in open field near stream, 1♀, S. Boucher leg. (all LEMQ); Buckinghorse Provincial Campground, Alaska Highway DC-175 (281.6 km), 27.vi.1978, 1♀, P. H. Arnaud leg. ; Chetwynd , 615 m, 25.vi.1978, 1♂, P. H. Arnaud, Jr. leg. ( CASC) ; Fort Nelson , 10.vi.1948, 1♀, W. R. Mason leg. ( CNCI) ; Glacier National Park , ca. 1.6 km N Glacier, 14.vii.1974, 1♂, P. H. Arnaud, Jr. leg. ( CASC) ; Haines Cutoff , 900’, 13.vii.1948, 2♂, W. R. Mason leg. ( CNCI) ; Kimpton Creek, Hwy. 93, 23.vi.1982, 6♂ 9♀, B. V. Peterson leg. ( CNCI, 1♂ 1♀ genit. prep.) ; Kinbasket Lake , BC Hydro drawdown study, Malaise trap, Beauchesne & Assoc Ltd. leg., 12.vi.2010, 08MCOT15, 1♀ ( RBCM) ; as above but 4.vii.2010, 83MCOT01, 1♂ (genit. prep.), 84MTRTb01, 1♀; as above but 10.vii.2010, 00MRFTb15, 1♂, 87MLRT01, 1♂, 87MTRTb15, 1♀, 88MCOT15, 1♂ 1♀; as above but 18.vii.2010, WIL83-15, 1♂, RFT84-15, 1♀ (all RBCM) ; Mt. Robson Prov. Pk., Hwy #16, small road towards Mt. Robson , 53°03’N 119°15’W, forest floor, swamp, ( Universität Bielefeld , Ca 1519), 6.viii.2002, 1♂, M.v.Tschirnhaus leg. ( ZSMC) ; Summit Lake, mi.392, Alaska Hwy. , 4500’, 8.vii.1959, 2♂ 2♀ (all genit. prep.), R. E. Leech leg. ; 10 mi W Terrace , farm plot, 13.vii.1960, 1♀, C. H. Mann leg. ; Kleanza Cr. , 14 mi E Terrace, 14.vii.1960, 2♂ 1♀ (all genit. prep.), G. E. Shewell leg. (all CNCI) . Manitoba: Churchill , 13.viii.1949, 1♀, L. A. Miller leg. ( CNCI) ; Churchill , 58.7400°N 93.8200°W, 15 m a.s.l., 6.viii.2010, 1♀ (Barcode of Life, Sample ID#10 PROBE-13016) ; Churchill, old dump, 58.7568°N 94.0317°W, 8 m a.s.l., 14.vii.2010, 1♂ ( Barcode of Life , Sample ID#10 PROBE-14479), 19.vii.2010, 3♀ (10PROBE-16868, -69, -70), all J. Wang leg. (all BIOUG, in ethanol) . Newfoundland & Labrador: Goose Bay , 2.vii.195[?], 1♂, J. J. Tibbles leg. ( CNCI, genit. prep.) . Northwest Territories: Fort McPherson , 2.vii.1957, 2♂, S. D. Hicks leg. ; as above but 10.vii.1957, 4♂ 2♀ (1♂ genit. prep.), 24.vii.1957, 1♂, R. Hurley leg. (all CNCI) . Quebec: Gaspé, ZEC [Zone d’Exploitation Contrôlée] York-Baillargeon, shore of Lac Ross , 48°49’N 64°52’W, sweep, 26.vii.2000, 1♂, H. Varady-Szabo leg. ( LEMQ, genit. prep.) ; Fort Chimo [Kuujjuaq], 2.vii.1954, 2♂ 2♀, W. R. Richards leg. ( CNCI, 2♂ 1♀ genit. prep.) ; Great Whale River , 8.viii.1959, 2♀, W. R. M. Mason leg. ( CNCI, 1♀ genit. prep.) . Saskatchewan: Saskatoon , 9.vii.1957, 1♀, A. R. Brooks ( CNCI) ; Sturgis , 51°56’N 102°32’W, 1.vii.1955, 1♂ 3♀, J. R. Vockeroth leg. ( CNCI, 1♂ 1♀ genit. prep.) ; White Fox , 18.vii.1941, 1♂, O. Peck leg. ( CNCI, genit. prep.) . Yukon Territory: Alaska Hwy. at Marshall Creek , 60°50.1’N 137°19.9’W, sweep grass at roadside, 18.vii.1998, 3♂, T. A. Wheeler leg. ( LEMQ, 1♂ genit. prep.) ; Carcross, Govt. Campground , 60°10.5’N 134°42.1’W, sweep vegetation at campsite, 20.vii.1998, 1♀, T. A. Wheeler leg. ( LEMQ) ; Dawson , 10.vi.1949, 2♀, W. W. Judd leg. ( CNCI, 1♀ headless) ; Donjek R., 19 km NW on Alaska Hwy. , 61°44’N 139°54’W, 23.vi.1981, 1♂, C. Guppy leg. ( UBCZ, genit. prep.) ; Klondike Hwy. , S of Carmacks, Montague Road House, sweep roadside vegetation, 11.vi.1997, 1♂, T. A. Wheeler leg. ( LEMQ) ; Klondike Hwy., 15 km S Carmacks, Bushy Mt. , 61°58.2’N 136°12.2’W, sweep vegetation in roadside parking area, 19.vii.1998, 1♂, T. A. Wheeler leg. ( LEMQ, genit. prep.) ; Tagish Campground , 60°19’N 134°15’W, sweep vegetation at camp site, 26.vi.1997, 1♂, T. A. Wheeler leg. ( LEMQ) ; as above but 60°18.8’N 134°16.1’W, sweep vegetation at camp site, 26.vi.1997, 1♂ 1♀, T. A. Wheeler leg. ( LEMQ, genit. prep.) ; Whitehorse, Bert Law Park at Yukon R., 60°42’N 135°02’W, sweep clearing in open forest, 27.vi.1997, 1♂, T. A. Wheeler leg. ( LEMQ) . UNITED STATES: Alaska: Anchorage , [no day]. vii.1960, 1♂, M. R. Wheeler leg. ( AMNH, genit. prep.) ; Big Delta , 4.vi.1951, 1♀, W. R. M. Mason leg. ( CNCI, genit. prep.) ; Kanuti NWR [National Wildlife Refuge], 66.2914°N 152.4376°W, 19-1, riverbank, birch forest, Malaise trap, 19.vii.2003, 1♀, H. Williams leg. ( UAM 100000629 ) ; Kenai Peninsula, 1 mi S jct. Hwy. #4 and Homer Rd. , No. 357, 30.vi.1957, 1♀, F. W. Preston leg. ( SEMC) ; Knik Lake , NW of Wasilla, sweeping vegetation edge of lake, 18.vii.1978, 1♂ P. H. Arnaud, Jr. leg. ( CASC, genit. prep.) ; Mat-Su, Talkeetna, Susitna River , 62°19.4’N 150°07.2’W, 4.viii.2003, 3♂, D. & W. N. Mathis leg. ( USNM ENT 00201105 , -06, -12, all genit. prep.) ; Ninilchik, trail to and about Russian Orthodox Church, Sterling Highway A-187, 25.vii.1978, 1♀, P. H. Arnaud leg. ( CASC) ; Palmer , jeep trap, 13.vii.1961, 2♂, K. Sommerman leg. ( USNM, both genit. prep.) ; Skagway , 5.vi.1981, 1♂, C. S. Guppy leg. ( UBCZ, genit. prep.) ; Unalakleet , 12.vii.1961, 1♀ (genit. prep.), B. S. Heming leg., 8.viii.1961, 1♀, R. Madge leg. ( CNCI) . Colorado: Jackson, Co., Rabbit Ears Pass , 7.vii.1961, 1♀, J. G. Chillcott leg. ( CNCI) ; Woodland Pk., Sta [tion] 3, 4.viii.1943, 1♂, H. H. Ross leg. ( INHS 40,191 , genit. prep.) .

Montana: 33 mi N West Glacier , 5.vii.1966, 1♂ 1♀, K. Valley leg. ( USNM, 1♂ genit. prep.) . Utah: Cache Co., Blacksmith Fork C [an]y[on], Grey Cliff Sp [rin]g, 24.viii.1984, 1♀, G. F. Knowlton leg. ( EMUS); Cache Co. , Tony Grove Jct., Malaise trap, 2–8.viii.1983, 1♂, [no collector] (genit. prep.), 11–25.vii.1984, 1♀, 1–13.viii.1984, 1♀, 1–7.ix.1984, 1♂, [no collector] ( EMUS); Cache Co. , Logan C [a]n[yon], Twin Cr., Malaise trap, 13–20.vii.1979, 1♂, [no collector] ( EMUS, genit. prep.); Cache Co. , Logan Canyon, Turner C [amp] G[round], 5–17.viii.1985, 1♀ (genit. prep.), 16–30.viii.1985, 1♂ 1♀ (1♂ genit. prep.), W. J. Hanson leg. ( EMUS); Grand Co. , LaSal Mtns., Warner C [a]n[yon], 9500’, 21.vii.1968, 1♂, W. J. Hanson leg. ( EMUS, genit. prep.); as above but Malaise trap, 21.vii.1968, 1♂ 1♀, [no collector] ( EMUS) ; San Juan Co., LaSal Mtns., Geyser Pass , 10200’, Malaise trap, 19.vii.1968, 1♀, [no collector] ( EMUS, genit. prep.) .

Other material not designated as paratypes (damaged):

CANADA: Alberta: ~ 26 km NW Highwood House, Mt. Lipsett pulloff, 50°33.26’N 114°57.27’W, sweeps, Bromus inermis , Leymus innovatus , 25.vii.2008, 1♀, K. N. Barber leg. ( DEBU, missing abdomen). British Columbia: Kinbasket Lake, BC Hydro drawdown study, Malaise trap, 25MCOT15, 21.vi.2010, 1♀, Beauchesne & Assoc Ltd. leg. ( RBCM, crushed).

Etymology: The species is named “disjuncta” (= separate, from Latin) for the separate female S7, a unique feature within the known species of the genus Arganthomyza .

Description: M a l e. Total body length 1.94–2.38 mm. Externally very similar to A. socculata including colouration, microtomentum and chaetotaxy; therefore only differences against the latter species are given below. Head slightly higher than that of A. socculata . Frons with colour and microtomentose pattern as in A. socculata but brown stripe on orbit behind posterior ors with denser grey microtomentum and duller. Frontal triangle with anterior corner usually dark brown and more acute. Parafacialia and gena light yellow, often with darker, silverygolden microtomentum. Cephalic chaetotaxy as in A. socculata but pvt often strongly crossed; vti usually markedly longer than other (vte, ors, vi) cephalic setae except for oc; 1 long fine vi (usually longer but weaker than anterior ors), subvibrissa weak, as fine as but longer than peristomal setulae (up to two-thirds of vi; exceptionally, in single male, subvibrissa as long as vi). Palpus as in A. socculata . Eye large, relatively broad, with longest diameter oblique and 1.3–1.4 times as long as shortest. Smallest genal height about 0.11 times as long as shortest eye diameter. Antenna entirely yellow, as in A. socculata . Arista 1.7–1.8 times as long as antenna.

Thorax with colouration, microtomentum and chaetotaxy as in A. socculata but sometimes with humeral (postpronotal) callus paler brown. Legs similar to those of A. socculata but f 1 with ctenidial spine hardly longer than maximum width of t 1, f 3 with a row of sparse posteroventral setae, distal 5–6 shorter and slightly thickened, and fore basitarsus with 2 longer but fine proximoventral setulae. Wing ( Fig. 170 ), including venation, closely resembling that of A. socculata . Discal (dm) cell moderate, with r-m situated distinctly in front of middle of dm cell. Apical portion of CuA 1 longer than dm-cu. Wing measurements: length 2.04–2.50 mm, width 0.73–0.91 mm, Cs 3: Cs 4 = 1.11–1.44, rm\dm-cu: dm-cu = 2.05–2.88. Haltere pale yellow, knob often more whitish.

Abdomen as in A. socculata except for as follows. T1 paler brown than T2 and only dorsally distinctly separate from the latter. S2 distinctly transverse, S3–S4 slightly transverse to almost as long as wide, both posteriorly wider than anteriorly; S5 transversely trapezoidal, posteriorly more or less emarginate. T6 transversely band-like but longer, medially somewhat desclerotized but not wholly depigmented (thus appearing attenuated but not interrupted).

Genitalia. Epandrium ( Figs 122, 123 ) blackish brown, somewhat larger, wider and more densely setose than that of A. socculata . Apart from 1 strong dorsolateral seta there are also several lateral relatively long setae; anal fissure wider, rounded subtriangular. Cercus rather large (as in all relatives), densely setose, with apical and preapical seta slightly longer than others. Medandrium ( Fig. 122 ) high, ventrally broadly incised (wider than in A. socculata ), dorsally tapered, with dorsolateral corners acutely projecting. Gonostylus ( Figs 122, 123, 128 ) ochreous to yellow, flat, slightly bent medially, more elongate than in A. socculata , tapered distally, with rounded apex, largely micropubescent on outer side and largely setose on inner side. Its anterior margin with more or less distinct concavity in the middle and posterior margin less concave than in A. socculata (in largest extension view). Hypandrium anterior to pregonite hardly or little excavated ( Fig. 124 ). Transandrium ( Fig. 125 ) also similar but medially shortly projecting to form base of caudal process being (as in A. socculata ) distally formed only by a pair of weakly sclerotized strips reaching to basal membrane. Pregonite with posterior lobe more robust and somewhat projecting ( Fig. 124 ); postgonite and armature of basal membrane not particularly different from those of A. socculata . Aedeagal part of folding apparatus with dark granulose tubercles on proximal part ( Fig. 127 ) reduced both in number and size in contrast to those of A. socculata . Connecting sclerite very slender, submembranous ( Fig. 127 ). Phallapodeme slender, with basal part somewhat more forked ( Fig. 121 ) than in A. socculata , and its apex very shortly bicuspidate ( Fig. 127 ). Aedeagus with short, frame-like phallophore and large distiphallus with very similar structures to those in A. socculata . Saccus somewhat more membranous but with the same rounded hyaline tubercles on apex as in A. socculata . Filum also very similar, only its flat pale-pigmented apex somewhat differing in shape of teeth and positions of micropubescence and microspinulae ( Fig. 126 ). Ejacapodeme as in A. socculata including slender digitiform projection.

F e m a l e ( Fig. 4 ). Similar to male unless mentioned otherwise. Total body length 2.10–3.02 mm. Mouthparts usually dark yellow to ochreous as in A. socculata but antenna with 3rd flagellomere usually darkened, at least with a brownish spot in proximal half. f 1 and f 3 as in female A. socculata . Wing measurements: length 1.90–2.90 mm, width 0.69–1.01 mm, Cs3: Cs4 = 1.07–1.36, rm\dm-cu: dm-cu = 1.96–2.94. Abdomen similar to that of A. socculata but S2–S5 becoming very slightly wider posteriorly and S5 distinctly wider than long (slightly narrower than S6).

Postabdomen ( Figs 130, 131 ) relatively short and wide. T6 large, broad particularly anteriorly, narrowed posteriorly, with paler posterior margin and setae in posterior half only. S6 relatively narrow and long, hence barely transverse, pale-pigmented and with very light both anterior and posterior marginal areas ( Fig. 131 ). Sclerites of 7th segment markedly different from those of A. socculata : T7 and S7 clearly disparate though closely attached. T7 larger and longer than in A. socculata , extended far onto ventral side and with spiracles embedded near its anteroventral corners ( Fig. 131 ). S7 large, wide and pale anteriorly, tapered, darker and with rounded corners posteriorly, entirely and distinctly micropubescent, with dark-pigmented transverse stripe near anterior margin and with 6 long setae at posterior to posterolateral margin ( Fig. 131 ). 8th segment partly membranous and finely micropubescent. T8 plate-shaped, dark except for posterior margin, anteriorly tapered and rounded as in A. socculata . S8 shorter than T8, medially divided and similarly formed and setose as that of A. socculata . Genital chamber (uterus) somewhat broader than that of A. socculata , with internal sclerotization formed by 1 pair of relatively simple, flat and pale-pigmented sclerites and 1 very elongate, narrow and (in profile) sinuously curved annular sclerite ( Figs 133, 134, 136 ). Ventral receptacle ( Fig. 132 ) hyaline, slender, relatively long, proximally wider tubular, distally suddenly tapered to form sinuate slender apical part with blunt tip; accessory gland small, hyaline, with some grains on surface, on slender, irregular and somewhat ringed duct. Spermathecae (1+1) resembling those of A. socculata , short-pyriform, with dark transversely striated surface but their slender bases provided with rosette of only 3 bell-shaped appendages (see Fig. 129 ) some of which have doubled apex; cervix very short and pale-pigmented; duct of spermatheca broad and short ( Fig. 136 ). T10 small, dark but less transverse than that of A. socculata , with sparse fine micropubescence and 1 pair of usual long medial setae. S10 ( Fig. 135 ) larger than T10, pentagonal, micropubescent and finely setulose in posterior two-thirds. Cercus relatively short and robust, with fine setae, apical and dorsopreapical being longest ( Fig. 136 ).

Discussion: Arganthomyza disjuncta sp. n. is closely related and extremely similar to the Holarctic A. socculata ( Zetterstedt, 1847) . The species is peculiar for the large and disparate female S7 (see Fig. 131 ), a character unknown in all other congeners where S7 is fused with T7 to form a compact annular tergosternum T7+S7. Although the disparate S7 surely is a plesiomorphic condition, it is here ( Fig. 173 , character 18, state 0) considered to have evolved secondarily in this species, as a reversal of the S7 integrated into the tergosternal ring which otherwise is a distinct synapomorphy of the genus Arganthomyza (see above under the genus).

While the female of A. disjuncta sp. n. can be easily identified by the separate S7, only 3 bell-shaped appendages on the spermatheca and the very elongate annular sclerite in the genital chamber, the distinction of the males of the new species from A. socculata is sometimes difficult. There are slight differences in the form of the gonostylus, hypandrium and pregonite (see the key and description above), it is true, but usage of these characters requires careful comparison and observation at various angles. The separation of males of these two species is moreover complicated by great variability of the gonostylus in both A. socculata and A. disjuncta sp. n. and the occurrence of unidentifiable specimens (those not possessing typical shapes of gonostylus, hypandrium and pregonite in combination) in localities where both species occur together (confirmed in Alaska).

Biology: Very little is known of the biology of A. disjuncta except the habitat would appear to be open and dominated by graminoids ( Figs 104, 105 ), most often by grasses (including the introduced weedy Bromus inermis Leyss ) based on label data from western North America. Riparian habitats have also been mentioned while “mouse runs” directs attention to the thatch layer (although most specimens have been swept from vegetation). This species co-occurs with A. socculata in some sites in Alaska. A single specimen of A. bivittata sp. n. and two specimens of A. duplex sp. n. (Cadomin, Alberta) were taken with a series of A. disjuncta sp. n. while a single specimen of A. disjuncta sp. n. was taken with a series of A. duplex sp. n. (Dunvegan, Alberta). Adults have been collected from 2 June to 1–7 September.

Distribution: Widely distributed in Canada (Alberta, British Columbia, Manitoba, Newfoundland and Labrador, Northwest Territories, Quebec, Saskatchewan, Yukon Territory) especially in montane areas of Alberta and British Columbia. Transcontinental though collected infrequently and mostly in northerly sites east of Saskatchewan (Churchill, Manitoba; Kuujjuaq, Great Whale River, and Gaspé, Quebec; Goose Bay, Newfoundland and Labrador)—notably with old records from south-central Saskatchewan (Saskatoon, Sturgis, White Fox) and no records from Ontario. Also known in the United States (Alaska, Colorado, Montana, and Utah) with at least some Utah records from high elevation.

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 121–128. Arganthomyza disjuncta sp. n. (male paratype, Canada: Alberta). 121—base of phallapodeme, dorsal. 122—external genitalia, caudal. 123—ditto, lateral. 124—hypandrial complex, lateral. 125—transandrium, caudal. 126—apex of filum of distiphallus, anteroventral (widest extension). 127—aedeagal complex, lateral. 128—gonostylus, lateroventral (widest extension). Scales: Figs 126, 128 = 0.05 mm, others = 0.1 mm.

FIGURES 129–136. Arganthomyza disjuncta sp. n. (female paratype, Canada: Alberta). 129—spermathecae. 130—postabdomen, dorsal. 131—ditto, ventral. 132—ventral receptacle, lateral. 133—internal sclerites, ventral. 134—ditto, lateral. 135—S10, ventral. 136—apex of postabdomen and female genital chamber, lateral. Scales: Figs 130, 131 = 0.2 mm, Figs. 135, 136 = 0.1 mm, other = 0.05 mm.

FIGURES 170–172. Wings of Arganthomyza species. 170—A. disjuncta sp. n. (male paratype, Canada: Alberta). 171, 172—A. socculata (Zetterstedt) (males, USA: Alaska). 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).