Arganthomyza acuticuspis, 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 : 18-21

Arganthomyza acuticuspis sp. n.

Figures 1 , 67–81 , 167

Type material: Holotype ♂ labelled: “USA: NM: Torrance Co., Manzano Mts , 12 mi W Manzano [34°37.4’N 106°24.8’W], Red Canyon Cmpgd, 8000’, 27–30.viii.1993, J. E. O’Hara, malaise trap ” and “ HOLOTYPUS ♂, Arganthomyza acuticuspis sp.n., J. Roháček & K. N. Barber det. 2011” [red label] ( CNCI, intact) . Paratypes: UNITED STATES: Arizona: Coconino Co., Flagstaff, 7100’, pond[erosa] pine meadow, Malaise , 18–25.vii.1979, 1♂, S. &. J. Peck leg. ( DEBU) ; Cochise Co., Rustler Park , 15.vi.1951, 1♀, M. R. Wheeler leg. ( AMNH) ; Cochise Co., Cor [onado] Nat. For. , Rustler Park , 15.viii.1976, 1♀, S. Frommer leg. ( UCRC ENT 79388) ; Cochise Co., Chiricahua Mts., Rustler Park , 1.vii.1973, 1♀, [no collector] ( OSAC) ; Graham Co., Hospital Flat, Pinaleno Mts. , alt. 8950’, 2.viii.1965, 1♀, H. B. Leech leg. ( CASC) . New Mexico: same data as for holotype, 1♂ 4♀ (1♂ 3♀ LEMQ, 1♂ wing removed, 1♀, both genit. prep., 1♀ CNCI) ; Otero Co., Cloudcroft , 12.vii.1984, 1♀, W. F. Barr leg. ( WFBM, genit. prep.) .

Etymology: The species is named “acuticuspis” (= acute tip, from Latin, name in nominative singular) for its acutely pointed gonostylus.

Description: M a l e. Total body length 2.24–2.78 mm; general colour blackish brown ( Fig. 1 ), sparsely grey microtomentose and distinctly shining. Head bicolourous (dark brown and yellow), very slightly higher than long, rounded anteriorly in profile. Occiput dorsomedially concave, largely blackish brown (only ventral marginal area ochreous) and sparsely grey microtomentose but shining. Frons largely dull and yellow, only frontal (including ocellar) triangle brown to dark brown and shining. Frontal (and ocellar) triangle with sparse grey microtomentum; its narrowed and acutely projecting anterior corner yellow and dull. Ocellar triangle coloured and microtomentose as surrounding frontal triangle. Orbit largely yellow and entirely silvery white microtomentose, behind posterior ors usually darker, ochreous to pale brown; a silvery white microtomentose stripe between posterior part of orbit and frontal triangle broad and anteriorly connected with similarly microtomentose orbit and also very narrow marginal line of frontal triangle. Rest of frons yellow, without microtomentum but dull. Frontal triangle relatively short and narrow, reaching anterior third (its brown part only half) of frons. Frontal lunule yellow, small and narrow. Face narrow, medially weakly sclerotized and concave, all yellowish white, whitish microtomentose and dull; border line separating it from parafacialia ochreous to yellow. Parafacialia and gena also yellowish white but densely silvery white microtomentose; ventral marginal stripe on gena ochreous-brown and posteriorly dilated. Postgena yellow, posteriorly ochreous as also is ventral band of occiput. Mouthparts dirty yellow, with paler (whitish yellow) palpus and darker (ochreous-brown) clypeus and prementum. Cephalic chaetotaxy: pvt distinct but fine, with apices crossed; vti and oc subequal, very long, longest of cephalic setae; oc proclinate, slightly divergent; vte and posterior ors subequal, distinctly shorter than vti; 2 ors, anterior long, only slightly shorter than posterior; 1–3 microsetula(e) in front of the anterior ors; 3–4 pairs of medial microsetulae in front of frontal triangle; 1 inclinate short seta behind vte; postocular setulae relatively long and sparse (about 6–8), in single row; postgena with several setulae and 2 (1 longer) pale posteroventral setae; 1 rather weak vi (about as long as but finer than anterior ors); subvibrissa distinct, up to three-fourths of vi length but finer, longer than peristomal setulae; 6–7 fine peristomal setulae. Palpus slender, dirty yellow, with 1 fine dark ventral preapical seta (as long as but thinner than subvibrissa) and a number (about 10) of paler ventral setulae. Eye large, suboval, with longest diameter very slightly oblique, 1.3–1.4 times as long as shortest. Gena relatively high (deep), its shortest height about 0.14–0.15 times as long as shortest eye diameter. Antenna with scape and pedicel yellow; 1st flagellomere pale to whitish yellow, with short white pilosity including cilia on anterior margin. Arista pale brown, with somewhat thickened basal segment, 2.1–2.2 times as long as antenna, with yet shorter cilia than those on apex of 1st flagellomere.

Thorax very slightly narrower than head, blackish brown or with humeral (postpronotal) lobe paler brown, shining despite sparse greyish microtomentum. Pleural part of thorax also unicolourous dark brown ( Fig. 1 ), except for some paler sutures between sclerites. Mesonotal microsetae reduced; macrosetae very long. Thoracic chaetotaxy: 1 hu (as long as 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 (relatively 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 3–5 dc microsetae in front of them; ac microsetae reduced to 2–3 (often incomplete) medial pairs between suture and level of anterior dc; a few microsetae also between prs and dc lines; 2 sc, the short laterobasal often longer than hu, apical very long and robust, almost as long as posterior dc; 1 very fine but distinct ppl; 2 long stpl, anterior somewhat shorter and weaker, posterior almost as long as prs, and 2–3 upcurved pale setulae below them; ventral part of sternopleuron usually with 4 longer pale setae. Scutellum rounded triangular, slightly convex dorsally. Legs yellow, coxae and bases of femora lighter, only distal half to two-thirds of apical tarsal segments blackish brown and contrasting with rest of tarsi. f 1 with ctenidial spine relatively small, somewhat shorter than maximum width of t 1 and with a row of long posteroventral setae. f 3 with a long row of posteroventral setae, 7–8 of which in distal twofifths distinctly shorter and thicker; t 2 with relatively short ventroapical seta; all basitarsi proximoventrally with 1–2 longer pale hair-like setulae. f 2, t 1 and t 3 simply setulose. Claws relatively long (as are those of all Arganthomyza species ). Wing ( Fig. 167 ) moderately narrow, with pale ochreous veins and unicolourous hyaline membrane. C with small and relatively sparse 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 slightly bent (recurved) and terminally almost parallel to M. Discal (dm) cell moderate, with r-m situated slightly in front of the middle of dm cell. Apical portion of CuA 1 slightly longer than dm-cu and almost reaching wing margin; A 1 short, ending far from it. Alula small but relatively broad (as in A. socculata ). Wing measurements: length 2.35–2.64 mm, width 0.87–0.91 mm, Cs 3: Cs 4 = 1.09–1.23, rm\dm-cu: dm-cu = 2.00–2.40. Haltere with yellow stem and paler, yellowish white knob.

Abdomen with terga and sterna dark brown (terga darker), sparsely microtomentose, and distinctly shining. T1 and T2 almost separate, only laterally partly fused. T3–T5 subequal, broad, bent onto ventral side of abdomen. Preabdominal sterna medium sized, strongly sclerotized becoming slightly wider posteriorly; S1 short and transverse, bare and with darker posterior marginal stripe; S2 shorter than wide, S3 and S4 almost as long as wide; S5 largest, broad, strongly transverse, with slightly emarginate posterior margin and, therefore, shortest medially. T6 very short, transversely band-like, bare, brown but slightly right of medial line more or less desclerotized and unpigmented, hence seemingly divided. S6–S8 dorsally fused together. S6 (shorter than S7 and ventrally band-like) and S7 strongly asymmetrical, both with strongly sclerotized and darker anterior margin, S6 with 1 setula, S7 with 2 short setae; S8 long (longer than epandrium), with sparse setae in posterior half but largely without microtomentum and glossy.

Genitalia of similar construction to those of A. bivittata and A. duplex . Epandrium ( Figs 67, 68 ) brown to blackish brown, about as broad as that of A. duplex but shorter, with setosity moderate, only 1 dorsolateral seta distinctly long and robust, plus 1–2 setae somewhat longer; anal fissure (dorsally) relatively small and narrow, with small but distinct lateral notch (cf. Fig. 68 ). Cercus relatively large, flat, pale-pigmented and finely setose, with 2–3 apical and subapical setae longer than others. Medandrium ( Fig. 67 ) of medium high, about as broad as that of A. duplex , medioventrally shallowly emarginate, dorsally narrowed but with well-developed dorsolateral corners and posteromedial keel. Gonostylus ( Figs 67, 68, 73 ) flat, ochreous-yellow, in sublateral view of elongately subtriangular outline with acute tip, very slightly bent medially ( Fig. 67 ), markedly less than those of A. bivittata and A. duplex ; its outer side micropubescent except for anterior margin and apical fifth ( Fig. 73 ) and macrosetae restricted to inner side. Hypandrium ( Fig. 69 ) moderately robust. Transandrium ( Fig. 70 ) somewhat wider than in the above relatives, medially with simple, broad but rather short caudal process becoming distally membranous and pale-pigmented to merge into basal membrane. Pregonite ( Fig. 69 ) very low, slightly projecting ventrally but its posterior part separated from hypandrium by narrow membranous incision, with 2 posterior setae inserted in membranous area behind small dark lobe and 3 (1 long, 1 shorter and 1 small) anterior setae, all inserted on its inner side. Postgonite ( Fig. 69 ) slender, slightly tapered distally, with apical third most narrow and bent knee-like posteriorly, with wider proximal part darker, and provided with 1 anterior setula and usual grain-like sensilla. Basal membrane ( Figs 69, 70 ) with dense (more pigmented than in relatives), flat, spine-like excrescences. Aedeagal part of folding apparatus dorsally with a group of small dark granulose excrescences, ventrally with fine, flat and pale transverse tubercles and anteriorly with some fine striae. Connecting sclerite very slender, membranous, with very fine granulose structure ( Fig. 72 ). Phallapodeme resembling that of relatives, with basal part deeply forked, but fulcrum more parallel-sided and bicuspidate apex more dilated ( Fig. 72 ). Aedeagus with small phallophore ( Fig. 72 ) and large distiphallus basally with internal elongate sclerites. Ventral sclerite connecting phallophore with ventrobasal sclerite of distiphallus rounded rectangular. Saccus of distiphallus distally with relatively few and small hyaline tubercles and a finely granulose area near them. Filum robust proximally (wider than that of A. bivittata but not as dilated as that of A. duplex ) formed by 2 closely attached and partly fused ribbon-like sclerites (the wider pale, the narrower dark, Fig. 72 ) becoming slender apically but its submembranous apex widened, flat and curved, terminated in several bent projections one of which represents continuation of the dark narrower sclerite ( Fig. 71 ), all almost devoid of microspinulae. Ejacapodeme most similar to that of A. duplex including slender digitiform projection with somewhat clubbed apex.

F e m a l e. Similar to male unless mentioned otherwise. Total body length 2.30–3.05 mm. First antennal flagellomere externally partly (particularly in anterodorsal half) ochreous-darkened. f 1 with ctenidial spine longer, about as long as or slightly longer than maximum width of t 1. f 3 posteroventrally simply setulose. Wing measurements: length 2.46–2.94 mm, width 0.85–1.03 mm, Cs 3: Cs 4 = 0.98–1.17, rm\dm-cu: dm-cu = 1.83–2.50. Abdomen with preabdominal sclerites shorter and more transverse. T1 distinctly shorter and often paler than T2. T3 and T4 of the same length, T5 often slightly longer than T4. T2–T5 all sparsely setose. Preabdominal sterna somewhat narrower than in male, paler brown than terga, finely setose. S1 short, transverse and wider than S2, bare, with dark posterior transverse stripe; S2 somewhat transverse, trapezoidal, anteriorly broader than posteriorly, slightly wider and darker than S3; S3–S5 becoming wider posteriorly: S3 as long as wide, S4 slightly wider than long, S5 largest, wider than long and distinctly transverse, widest posteriorly (but narrower than the distinctly darker S6).

Postabdomen ( Figs 75, 76 ) of medium length, basally broad, distally tapered. T6 large but distinctly shorter and more transverse than in A. bivittata and A. duplex , setose in posterior half. S6 much smaller and narrower than T7+S7, darker pigmented than T6, more transverse than in above relatives, with long setae at posterior and lateral margins. T7 and S7 completely fused into largely dark brown ring-shaped tergosternum T7+S7, dorsally shorter ( Fig. 75 ) and with lighter anterior marginal area, ventrally longer ( Fig. 76 ), with both posterior and anterior palepigmented areas but the latter with long, dark, finely sinuate transverse ledge-like band and spiracles situated at its lateral ends. Ventral side of T7+S7 without markedly distinct micropubescence but with usual long setae at posterior margin. Membrane of 8th segment densely micropubescent. T8 slightly elongate, anteriorly rounded, posteriorly shallowly emarginate to straight, pigmented (but paler than T10) and with long micropubescence. S8 slightly shorter but not wider than T8, medially divided and forming 2 finely setose sclerites, both posterodorsally recurved and invaginated inside 8th segment (see Fig. 81 ). Genital chamber medium broad ( Fig. 81 ), in distal wider part, near insertion of ventral receptacle, with distinct plate-shaped and partly divided (subquadrangular in ventral view) sclerite; the usual proximal internal sclerotization formed by 1 pair of simple, flat but crooked sclerites and 1 narrow, flattened annular sclerite ( Figs 79, 80 ) differing from those of relatives by smaller size and conspicuously widened anterior part. Ventral receptacle ( Fig. 78 ) slender and elongate, of the same general form as in A. bivittata and A. duplex including middle part curved and somewhat ringed, long terminal part simply tubular and apex vermicularly twisted. Accessory gland hyaline, irregularly vesiculate, on relatively short duct dilated in distal twothirds. Spermathecae (1+1) short-pyriform to subcylindrical ( Figs 74, 77 ), both of the same size, each more or less constricted in proximal third, with dark transversely striated (striae interrupted) surface in distal two-thirds, and with a number of small dark spines in narrower basal part around duct insertion; duct short ( Fig. 81 ), with palepigmented cervix ( Fig. 77 ). T10 small, transverse ( Fig. 75 ; shorter than in relatives), relatively dark-pigmented particularly laterally, with reduced micropubescence and 1 pair of very long medial setae. S10 paler, markedly larger than T10, short-pentagonal ( Fig. 76 ) and micropubescent in posterior two-thirds. Cercus pale-pigmented, moderate in length and width, with fine setae, dorsopreapical and apical longest ( Fig. 81 ).

Discussion: Arganthomyza acuticuspis sp. n. belongs together with A. bivittata sp. n. and A. duplex sp. n. to the A. duplex group (as defined in discussion under A. duplex ). Based on our phylogenetic analysis (see Fig. 173 ) it is the sister group of A. bivittata + A. duplex .

Arganthomyza acuticuspis sp. n. differs distinctly from both its closest relatives by the following characters: pleurae uniformly dark brown, gonostylus acutely pointed, female preabdominal sterna brown and an additional plate-shaped sclerite in the female genital chamber (see Fig. 81 ) not to mention other details in the male and female terminalia. It can be separated from other externally similar (dark-coloured) Arganthomyza species using the key above and by male genitalic (acute gonostylus, filum proximally broad, form of apex of filum) and female postabdominal (shape and pigmentation of T7+S7, spermathecae, ventral receptacle, internal sclerites of female genital chamber) characters.

Biology: Virtually nothing is known about the biology of this species. Dr. James O’Hara (CNCI) provided some photos from 1999 of the typical habitat where he placed his Malaise traps in the Manzano Mts., including the Red Canyon Campground, where the holotype and a series of paratypes were collected in 1993. He also provided a photo of similar habitat at Hospital Flat (Pinaleno Mts.), a collection site for another paratype taken by Dr. H. B. Leech in 1965. Generally, these habitats are open meadows dominated by grasses and wildflowers bordering and surrounded by coniferous forests. They are likely similar to the “ponderosa pine meadow” noted on the Flagstaff paratype record. This generalized habitat is more reminiscent of the open “grassy” habitat of A. disjuncta n. sp. than of other members of the A. duplex group that are associated with a more mesic mixed forest with dense herbaceous undergrowth (at least in eastern North America). Flight period runs minimally from 15 June to 15 August (Rustler Park, Arizona) but this short period is probably an artifact of insufficient data.

Distribution: This poorly collected species is known only from elevated sites (7100’ to 8950’) in Arizona and New Mexico of the southwestern United States.

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 67–73. Arganthomyza acuticuspis sp. n. (male paratype, USA: New Mexico). 67—external genitalia, caudal. 68—ditto, lateral. 69—hypandrial complex, lateral. 70—transandrium, caudal. 71—apex of filum of distiphallus, subventral (widest extension). 72—aedeagal complex, lateral. 73—gonostylus, sublateral (widest extension). Scales: 0.1 mm.

FIGURES 74–81. Arganthomyza acuticuspis sp. n. (female paratype, USA: New Mexico). 74—spermatheca. 75—postabdomen, dorsal. 76—ditto, ventral. 77—spermatheca. 78—ventral receptacle, lateral. 79—internal sclerites, ventral. 80—ditto, lateral. 81—apex of postabdomen and female genital chamber, lateral. Scales: Figs 75, 76 = 0.2 mm, Figs 78–81 = 0.1 mm, others = 0.05 mm.

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.