Arganthomyza hyperseta, Roháček, 2018

Roháček, Jindřich, 2018, First Anthomyzidae (Diptera) from China: a new genus, six new species and new records, Acta Entomologica Musei Nationalis Pragae 58 (1), pp. 35-76 : 71-74

Arganthomyza hyperseta sp. nov.

( Figs 119–128 )

Type material. HOLOTYPE:, labelled: “[Shaanxi: Zuoshui-x], Brook nr tunnel, He-taoping, 1650-1750m, 22 June 1997, A. NAKANISHI col.” and “ Holotypus, Arganthomyza hyperseta sp. n., J. Roháček det. 2017” (red label). The holotype is now housed at the Saigusa Institute of Insect Natural History ( SIINH, genit. prep.) in Fukuoka, and will eventually be donated to an authorized collection in China that is not yet determined.

Description. Male. Total body length 2.14–2.42 mm; general colour blackish brown, unusually lustrous (probably the shiniest species of Anthomyzidae ) due to very reduced microtomentum ( Fig. 119 ). Head somewhat higher than long, with frons only slightly produced in front of eye, thus relatively rounded anteriorly in profile. Occiput dorsomedially concave, entirely blackish brown, glabrous and shining, almost devoid of microtomentum. Frons also largely shining, with anterior half yellow to (posteriorly) orange, remainder blackish brown. Frontal triangle yellow anteriorly and dark brown posteriorly, bare and lustrous except for apex of anterior corner being whitish microtomentose and duller. Ocellar triangle small, shining, without microtomentum. Ocelli closely positioned, distance between them very slightly longer than ocellar diameter. Orbits anteriorly (from anterior margin of frons margin up to posterior ors) yellow and sparsely silvery white microtomentose, posteriorly blackish and polished; a very distinct silvery microtomentose stripe between posterior part of orbit and frontal triangle extending from posterior ors to vti. Frontal triangle very long, almost reaching to anterior margin of frons. Frontal lunule orange, small, narrow. Face very narrow, medially weakly sclerotized, deeply depressed and somewhat folded, dirty yellow and sparsely whitish microtomentose. Parafacialia and gena whitish yellow and densely silvery white microtomentose, having pale brown marginal stripe continued on ventral margin of gena and posteriorly dilated and connected with dark brown and relatively shining postgena. Mouthparts small, dirty yellow including palpus; clypeus not visible in the holotype. Cephalic chaetotaxy: macrosetae longer than in relatives ( Fig. 119 ) but pvt relatively short, weak, but strongly crossed; vti very long (longer than shortest eye diameter), distinctly longest of cephalic setae; oc also long but shorter than vti, proclinate and parallel; vte and posteri- or ors subequal and slightly shorter than oc; 2 ors, anterior markedly shorter and weaker (less than third as long) than the long posterior ( Fig. 119 ); 1 microsetula (rather far) in front of the anterior ors; 2 pairs of medial microsetulae at sides of anterior corner of frontal triangle; 1 inclinate setula behind vte distinct, as long as uppermost postocular setulae; the latter sparse (6–7) and dark, in single row; postgena with several setulae and 2 (1 longer) posteroventral setae; 1 long vi (as long as but weaker than posterior ors); subvibrissa reduced, not longer than anterior peristomal setula; only 5–6 fine peristomal setulae. Palpus slender, yellow, with 1 fine dark ventral preapical seta (distinctly longer than subvibrissa) and a few ventral setulae. Eye large, suboval, with longest diameter nearly vertical and about 1.5 times as long as shortest. Shortest genal height about 0.10 times as long as shortest eye diameter.Antenna slightly geniculate; scape and pedicel orange yellow; 1st flagellomere laterally flattened, largely whitish yellow, darker yellow only around base of arista (not brownish dorsally as in A. versitheca Roháček, 2009 ), with dense short pilosity but its anterior margin with comparatively long white ciliation. Arista brown including thickened basal segment, about twice as long as antenna, relatively long ciliate (cilia as long as those on 1st flagellomere).

Thorax slightly narrower than head, entirely blackish brown and largely strongly lustrous because of reduced microtomentum ( Fig. 119 ). Mesonotum and most of humeral callus lacking microtomentum and glabrous, only ventral margin of the latter and of notopleural area, a small posterolateral spot (between posterior npl, sa, pa and base of scutellum) and scutellum with sparse grey microtomentum and subshining. Pleural part of thorax, postscutellum and postnotum completely blackish brown and sparsely pale grey microtomentose but also relatively shining. Thoracic chaetotaxy: mesonotum with reduced number of microsetae; macrosetae very long, some yet longer than those of relatives. 1 hu (somewhat shorter than anterior npl); 2 npl (posterior distinctly shorter); 1 very long prs (much longer than anterior npl); 1 very long sa (as long as prs); 1 pa (only about as long as anterior npl); 2 very long postsutural dc (posterior longest of thoracic setae, anterior shorter but also very long, slightly longer than sa or prs) and 5 dc microsetae in front of them; ac microsetae almost absent (only 1 can be seen between anterior dc pair); 2 sc, laterobasal weak, shorter than pa, apical very long, almost as long as posterior dc; 1 medium long but very fine upcurved ppl; 2 relatively long but thin stpl, anterior only slightly shorter than posterior, and 2 upcurved pale setulae below them; ventral part of sternopleuron with 3 longer pale setae. Scutellum relatively narrow (only about 1.5 times as wide as long), rounded triangular, strongly convex dorsally. Legs yellow to pale yellow ( Fig. 119 ), coxae and trochanters yellowish white, only distal half to two-thirds of apical tarsal segments dark brown. f 1 with ctenidial spine slightly longer than maximum width of t 1 and with a row of very long posteroventral setae (longest twice longer than those in posterodorsal row). f 3 with a row of posteroventral setae but only 4 in distal third shortened and distinctly thickened; t 2 with 1 small anteroapical seta and 1 relatively short ventroapical seta; also t 3 with 1 short but distinct anteroapical seta; fore basitarsus with 2 longer proximoventral hair-like setulae; mid basitarsus with distinct proximoventral seta ( Fig. 120 ) being subequal to ventroapical seta on t 2 (cf. also Fig. 117 ); hind basitarsus ( Fig. 118 ) with a single robust proximoventral seta; f 2, and t 1 simply setulose. Wing ( Fig. 119 ) about as long as body length (of air-dried specimen) and relatively narrow, with pale ochreous veins and hyaline membrane. C with small and sparsely arranged spinulae between apices of R 1 and R 2+3. R 2+3 long, slightly sinuous because it runs parallel to C with apex upcurved to C; R 4+5 very slightly bent, subparallel to C but converging preapically to (almost straight) M. Discal (dm) cell moderate, with r-m situated slightly in front of middle of dm cell. Apical portion of CuA 1 somewhat longer than dm-cu, ending close to wing margin; A 1 short, ending far from it; anal lobe not reduced; alula small, narrow, with apex rounded. Wing measurements: length 2.46 mm, width 0.74 mm, Cs 3: Cs 4 = 1.69, rm\dm-cu: dm-cu = 2.80. Haltere with yellowish white knob; stem yellow but basally darker, orange ochreous.

Abdomen ( Fig. 119 ). Preabdominal terga blackish brown and shining despite very sparse grey microtomentum; sterna dark brown, more densely microtomentose and subshining. T1 and T2 largely separate, only laterally partly fused. T2 somewhat narrower and shorter than T3, T3–T5 subequal, broad, bent onto ventral aspect of abdomen, all relatively finely and sparsely setose. Preabdominal sterna relatively large, well sclerotized; S1 and S2 not studied; S3–S5 becoming wider posteriorly, S3 and S4 subequal in length, both wider than long; S5 ( Fig. 125 ) widest but shorter than S4, transversely trapezoidal, with setae (those at posterior margin long) separated by a medial bare area. T6 very short, transversely band-like, bare, brown, undivided but with medial third unpigmented. S6–S8 dorsally fused together. S6 (as long as S7 but ventrally band-like) and S7 strongly asymmetrical, both with strongly sclerotized anterior ledge-like margin; S6 with 2 setae, S7 with 1 seta; S8 twice as long as than S7 (and about as long as epandrium), tapered posteriorly, with sparse setae in posterior half.

Genitalia. Epandrium ( Figs 121, 123 ) dark brown, moderately broad, with relatively long but fine setae, including 2 (or 3) distinctly longer and thicker pairs, the dorsolateral being very long; anal fissure rather large, rounded triangular. Cercus relatively large, robust but pale-pigmented, densely finely setose, with 2 apical setae slightly longer than others. Medandrium ( Fig. 121 ) relatively high, tapered dorsally with relatively acute dorsolateral corners. Gonostylus ( Figs 121, 123, 126 ) slightly shorter than epandrial height, flat, bent medially, with ham-shaped outline as in relatives ( A. versitheca in particular) but narrower and with more tapered apex, finely micropubescent on most of outer side and relatively shortly setose on inner side. Hypandrium ( Fig. 124 ) different from that of relatives, with distal (anterior) end slender, and posterior half gradually strongly dilated and posteriorly fused with relatively robust transandrium. Transandrium ( Fig. 122 ) not separated from hypandrium, rather pale-pigmented except for very slender, more sclerotized and dark dorsal marginal ledge, without distinct caudal process, hence ventromedially transient to basal membrane. Pregonite ( Fig. 124 ) reduced and fused to hypandrium, very low, hardly projecting ventrally but bent internally, with 3 relatively short anterior (internal) and 2 yet shorter posterior (external) setae (but both groups very close). Postgonite ( Fig. 124 ) elongate, somewhat bent, distinctly pigmented and with apex transient to larger posterior submembranous lobe; its anterior margin with only a series of several minute setulae (2 slightly longer), without distinct seta. Basal membrane ( Figs 122, 124 ) with dense, flat, spine-like excrescences being smaller and pale dorsally and larger and darker ventrally. Aedeagal part of folding apparatus ( Fig. 128 ) with only a group of small, inconspicuous flat and pale tubercles and some fine striae. Connecting sclerite indistinct, slender and membranous. Phallapodeme distinctly different from that of relatives, unusually slender including fulcrum and simple rod-like apex, although with basal end deeply forked as in relatives. Aedeagus with short, frame-like but heavily sclerotized phallophore ( Fig. 128 ) and rather voluminous distiphallus. Saccus short but distally broad, with proximal part narrower and distinctly sclerotized and membranous distal part relatively voluminous, apically covered with numerous small hyaline tooth-like tubercles, otherwise unarmed. Filum yet more robust than that of A. versitheca , rather compact (with original longitudinal flat sclerites largely fused) but pale-pigmented and not strongly sclerotized; its apex ( Fig. 127 ) widened, curved and partly membranous, with several flat lobe-shaped (some with fine spinulae) projections and a few acute teeth, distinctly different from both A. versitheca and A. carbo. Ejacapodeme not observed, probably lost during dissection of genitalia.

Female unknown.

Discussion. Arganthomyza hyperseta sp. nov. belongs to the A. setiplanta group as characterized by ROHÁČEK & BARBER (2013, 2016). This group comprises A. setiplanta ( Roháček, 1987) from Nepal, A. versitheca Roháček, 2009 from South Korea (also recorded from China: Shaanxi, Sichuan below) and A. carbo Roháček & Barber, 2013 from Canada and USA. The new species is externally very similar to representatives of this group including the long macrosetae of head and thorax and colouration of all parts of body but differs distinctly from all of them in having the mesonotum extremely glossy, almost without microtomentum. Further (less striking) differences from these species can be found in the head colouration (with yellow anterior half of frons and orbits up to posterior ors, occiput without microtomentum) and chaetotaxy (pvt crossed, vti extremely long, anterior ors very small), thoracic chaetotaxy (prs, sa and dc longest of all relatives, Fig. 119 ), male f 3 with only 4 short thickened setae in posteroventral row and hind basitarsus with only 1 robust proximoventral seta ( Fig. 118 ).

Based on the construction of the male genitalia, A. hyperseta seems to be the closest relative of A. versitheca sharing with the latter the narrower apex of the gonostylus and the broad filum of the distiphallus. However, there are several species-specific characters also in the male genita- lia distinguishing the new species from both A. versitheca and A. carbo (male unknown in A. setiplanta), particularly the epandrium with more triangular anal fissure and the very long dorsolateral setae ( Fig. 121 ), apex of gonostylus most tapered ( Fig. 126 ), hypandrium with anterior half narrow and posterior half unusually dilated ( Fig. 124 ), transandrium more robust and gradually transient to basal membrane and the latter with somewhat bilobed spinose armature ( Fig. 122 ), phallapodeme unusually slender and with simple apex ( Fig. 128 ), saccus very broad and more tuberculate apically ( Fig. 128 ), filum most robust and with complex and very distinctive apex ( Fig. 127 ). Also the male pregenital sternum (S5) is distinctive in its chaetotaxy ( Fig. 125 ). Because the female of A. hyperseta and the male of A. setiplanta remain unknown, the possibility that these two species could be more closely related cannot be excluded; however, the distinctly shorter frontal triangle, more ac microsetae and distinctly microtomentose mesonotum of A. setiplanta speak against this possibility and indicate that A. setiplanta is probably the most ancestral species of the group as hypothesized by ROHÁČEK & BARBER (2013, 2016).

Etymology. The species is named for its strikingly long mesonotal macrosetae. The name is a a Latin noun (composed of prefix hyper - and a noun seta) in apposition in nominative singular.

Biology. Habitat association of the new species is unknown. The holotype male was collected in June at 1650–1750 m.

Distribution. China: Shaanxi.

Figures

Figs 117–119. Arganthomyza hyperseta sp. nov., male holotype (China: Shaanxi). 117 – apex of t2 and mid basitarsus, ventrally; 118 – apex of t3 and hind basitarsus, posteriorly; 119 – holotype before dissection, laterally (body length ca 2.5 mm). Photos by M. Tkoč.

Figs 120–128. Arganthomyza hyperseta sp. nov., male holotype (China: Shaanxi). 120 – apex of t2 and base of mid basitarsus, anteriorly; 121 – external genitalia, caudally; 122 – transandrium, caudally; 123 – external genitalia, laterally; 124 – hypandrial complex (right side), laterally; 125 – 5th sternum, ventrally; 126 – gonostylus, laterocaudally (widest extension); 127 – apex of filum, anteroventrally; 128 – aedeagal complex, laterally. Scales = 0.2 mm (Figs 120, 125), 0.05 mm (Figs 126, 127), 0.1 mm (others).