Marshallya platythorax, 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 : 40-46

Marshallya platythorax sp. nov.

( Figs 1–4, 6–30 )

Type material. HOLOTYPE:, labelled: ‘ China: Sichuan: Emeishan , 19.v.2016, 800– 900m, N 29°34ʹ10.42ʺ E 103°23ʹ27.98ʺ, S.A. Marshall’ and ‘ Holotypus, Marshallya platythorax sp. n., J. Roháček det. 2017’ (red label). The specimen is intact, dried from ethanol and mounted on a pinned paper point, with only left mid leg removed and glued to the specimen pin ( CAU). PARATYPES: 1 1 ♀, with same label data as the holotype, only second (type) label is yellow and has ‘Paratypus’ instead of ‘Holotypus’; the male body (without abdomen, one wing and hind leg) was used for DNA extraction and subsequently placed (partly dissected) in glycerine in a pinned plastic microvial; abdomen of both male and female cleared, dissected and preserved in glycerine in a pinned plastic tube but that of male with the removed wing and hind leg in addition ( DEBU, 1 ♀; SMOC, 1).

Description. Male. Total body length 3.02–3.18 mm. Body elongate and very slender ( Figs 6, 7 ), bicolourous, dark brown and whitish yellow. Head slightly longer than high; frons flattened and dorsomedially depressed. Occiput distinctly concave, dark but not entirely (ochreous to ochreous yellow dorsally, particularly behind eyes), subshining and greyish microtomentose (most densely medially above foramen). Vertex with narrow silvery grey microtomentose stripes between ocellar triangle and posterior part of orbit. Frontal triangle very short (only in posterior third of frons) and roughly equilateral, shiny because of very sparse microtomentum, including ocellar triangle. Ocelli large and close to each other. Frons largely dark brown, dark grey microtomentose and dull, only its narrow medial band pale brown to ochreous yellow (anteriorly) and anterior half of orbit yellow. Orbit dark brown and shining in posterior half but becoming lighter anteriorly to dirty yellow and whitish grey microtomentose in anterior third. Frontal lunule very reduced, not visible in dry specimens. Face dark ochreous laterally, brown and distinctly concave medially; parafacialia and (most of) gena whitish yellow, with silvery white microtomentum but both pale brown margined (on anterior part of gena most broadly); postgena with posteroventral corner almost rectangled ( Fig. 3 ) but rounded, whitish yellow, dorsally concolourous with adjacent dark brown part of occiput. Mouthparts relatively small, dirty yellow including somewhat darker clypeus. Cephalic chaetotaxy ( Fig. 3 ): pvt small but distinct, convergent (usually) to parallel; vti distinctly shorter than vte (about two-thirds of the latter); vte and/or posterior ors longest of cephalic setae; oc strongly proclinate, only about as long as vti, situated outside line connecting ocelli; 2 widely spaced and long ors, posterior as long as or longer than vte, anterior only slightly shorter; 1 setula and 1 much smaller microsetula in front of anterior ors; 2 pairs of microsetulae in interfrontal position in anterior third of frons; 1 relatively weak vi (about as long as oc) and 1 almost equal subvibrissa; peristomal setulae (6–7) fine, becoming longer anteriorly, the foremost about half length of vi; postocular setulae very minute, in single row behind dorsal half of posterior eye margin; palpus whitish yellow, with usual subapical (as long as foremost peristomal) and 2 smaller setulae on apex. Eye large, orange red (when alive, cf. Figs 6, 7 ), ellipsoid (almond-shaped) as in Amygdalops species and covering most of head profile, very convex, with longest diameter about 1.6 times as long as shortest one. Gena very narrow; its shortest height 0.08 times as long as shortest eye diameter. Antenna ( Fig. 2 ) yellow, strongly geniculate; scape and pedicel of usual form and setosity; 1st flagellomere strongly laterally flattened, entirely yellow, at most with slightly darker margin around base of arista, shortly whitish ciliate on apex. Arista also yellowish, including short and thick basal segment, about 2.2 times as long as antenna, with medium long whitish ciliation ( Fig. 2 ).

Thorax narrower than head (with eyes), bicolourous, dark brown dorsally and yellowish white ventrally. Dorsal part of thorax sparsely microtomentose and relatively shining, pleural part duller. Mesonotum dorsally flattened (see Figs 6, 7 ), largely dark brown but with paler ochreous brown anterior spots adjacent to humeral callus and also dorsocentral lines somewhat paler ( Fig 3 ). Humeral (postpronotal) callus pale brown and also notopleural area somewhat lighter than surrounding sclerites; pleural part of thorax with rather broad (covering entire propleuron and dorsal half of mesopleuron) blackish brown dorsal band extending from propleuron to haltere and sharply delimited from yellowish white ventral portion of pleuron. Scutellum slightly convex (not flat) and blackish brown, as are the well developed (bulging) postscutellum and metapleuron. Thoracic chaetotaxy ( Fig. 3 ) reduced: ppl, prs and sa absent; 1 relatively weak hu, 2 npl (anterior slightly longer than hu, posterior short), 2 (both postsutural) dc arising close to scutellum; anterior dc short (only twice the length of dc microsetae) and situated immediately in front of the long posterior dc, the latter only slightly shorter than apical sc; ac microsetae small and sparse, in 4 rows on suture, in 2 rows between dc macrosetae and reaching to prescutellar position; 1 short pa (not longer than laterobasal sc); 2 sc, apical long and strong (the longest thoracic seta), laterobasal small, less than one third of length of apical sc and situated rather far from base of scutellum; 2 stpl, posterior only slightly longer than anterior; 5–6 microsetae below stpl and a number (about 10) of fine setae on ventral corner of sternopleuron. Scutellum rounded triangular, about 1.5 times as wide as long. Legs bicolourous, largely yellow to yellowish white (coxae lightest) but femora with diffuse brown darkening in distal third to half (except for yellow apical part at knees) and with tibiae similarly (somewhat paler) brown-darkened in proximal fourth to third (cf. Figs 3 , 10 , 27 ). Pedal chaetotaxy: f 1 with usual posterodorsal and posteroventral row of longer setae but also with an anteroventral comb of short and thicker setae (3–4 usually more robust than others) in distal two-fifth (see Fig. 27 ); f 2 without peculiarities, only with some slightly longer and erect ventral setae in proximal third; f 3 with posteroventral row of setae along entire length (4–5 of them in distal half shortened and thickened) and with an additional anteroventral row of several (yet shorter) thickened setae (see Fig. 10 ). t 1 and t 3 uniformly setulose; t 2 with usual ventroapical seta, distinctly longer than maximum width of tibia; basitarsi of all legs with 1–3 longer and somewhat thicker ventrobasal setulae, being larger (2–3) on hind basitarsus which also bears a series of thicker ventral setulae among fine setulae. Wing ( Fig. 1 ) with distinctly brown darkened membrane, darkest along distal half of R 2+3 and between apices of the latter and R 4+5; veins dark brown. C (unlike Amygdalops species) with thicker spine-like, widely spaced, setae on dorsal side (cf. Figs 3, 4 ). Sc well developed, free proximally, attached to R 1 distally and forming with the latter a very distinct preapical kink at subcostal break. R 2+3 very long, running close to C, distally slightly sinuate and apically upcurved to C. R 4+5 distally slightly bent and converging preapically to slightly sinuate vein M and ending in parallel. Discal (dm) cell narrow but relatively long (longer than in most of Amygdalops species); r-m situated around basal two-fifths to third of dm cell; apical section of CuA 1 more than twice longer than dm and almost ending in wing margin; bm and cup cells small and narrow; A 1 short but almost reaching wing margin due to reduced anal lobe of wing. Alula small and very narrow (as in Amygdalops species). Wing measurements: length 2.98–3.02 mm, width 0.83–0.93 mm, Cs 3: Cs 4 = 2.08–2.19, r-m\dm-cu: dm-cu = 3.89–4.06. Haltere with brown stem and large dark brown knob.

Abdomen elongate and very narrow (about 4.6 times as long as wide), blackish brown, greyish microtomentose and subshiny dorsally, pale (whitish) ochreous ventrally. Preabdominal terga large, bent onto lateral to ventrolateral aspects (hence pleural part of segments reduced), uniformly blackish brown and relatively densely but shortly and finely setose. T1 distinctly separate and about half length of T2; T2 slightly shorter than T3 and/or T4 (these subequal); T5 shorter than T2 but widest of preabdominal terga. T6 not developed (membranous). Preabdominal sterna very pale, finely sparsely setose, becoming somewhat wider posteriorly, S5 the widest. S1 shorter than wide, bare; S2 with brownish stripe along anterior margin, slightly shorter than S3 and/or S4 (these subequal) and all distinctly longer than wide; S5 widest but shorter, about as long as wide. S6–S8 asymmetrical, dorsolaterally fused; both S6 and S7 lighter brown, subequal in length, each with anterior darkened marginal ledge-like stripe and situated on left side of postabdomen; S6 ventrally shortened, transversely band-like, laterally dilated, subrhomboidal, bare except for 2 microsetulae; S7 of pentagonal outline, bare, with fusion line with S6 thickened and darkened and its dorsal part embedding large 7th spiracle; 6th spiracle situated in membrane above dorsal corner of S6. S8 situated dorsally, blackish brown, long (almost 3 times as long as S7) and with a number of relatively short setae in posterior half.

Genitalia of distinctive construction. Epandrium relatively large (compared to postabdominal sclerites), hemispherical, not long ( Fig. 8 ) but broad (markedly wider than long, cf. Fig. 9 ), rather densely setose, with 1 dorsomedial and 1 laterocaudal (this longest and thickest) long setae; anal opening relatively large, high, narrowly semi-ellipsoid ( Fig. 9 ). Cercus characteristically formed, not small but only half length of gonostylus, strongly (dorsoventrally) flattened and hidden in anal fissure (hence not visible in lateral view), with longer setae mainly in dorsal half. Medandrium ( Figs 9, 11 ) comparatively broad, having only lateral parts well-sclerotized; dorsomedial connecti- on slender and submembranous. Gonostyli symmetrical, strongly bent medially (cf. Fig. 9 ), with apices crossed or appressed in rest position. Gonostylus ( Figs 8, 9, 13 ) long and relatively slender, roughly sickle-shaped in widest extension view ( Fig. 13 ); its anterior (basal) part with a group of longer fine setae ventrally, most of outer side covered by micropubescence, otherwise finely setose on inner side near posterior margin; apex of gonostylus with a pair of denticles (visible only at a limited viewing angle – Fig. 12 ). Hypandrial complex ( Figs 14, 15 ) of unique construction. Hypandrium robust (both in lateral and ventral view), with well developed dorsally projecting flat lateral lobes ( Figs 14, 15 , hl). Transandrium ( Figs 14, 15, 17 ) formed by simple medial sclerite (lacking medial caudal process, see Fig. 17 ) connecting robust lateral parts each projecting into a peculiar stump-like (caudal) process being anteroventrally connected with both postgonite and posterior part of pregonite (see Figs 14–17 , cp). Pregonite ( Figs 14, 15 ), elongate and low, incurved, only its anterior part somewhat projecting medially ( Fig. 15 , prg) and bearing a group of 5–6 setae; its inconspicuous posterior part with 4–5 setae. Postgonite ( Figs 14–18 , pg) very unusual, shifted laterally, lacking basal sclerite but anterodorsally fused to pregonite and posterodorsally to lateral caudal process of transandrium. Its form is uniquely short and complex, with several teeth (one of them with a distinct seta) and main lobe with series of setiform sensilla (cf. Fig. 18 ). Basal membrane ( Fig. 17 , bm) also peculiar in lacking any armature and being ventrally incised. Aedeagal part of folding apparatus ( Fig. 22 , afa) submembranous, relatively short and its external side with medium to small dark tubercles arranged in radial pattern; connecting sclerite ( Fig. 22 , cs) extremely robust, heavily sclerotized, proximally slender but becoming thicker in middle part, distally dilated and somewhat hook-like, with robust blackish angular apex projecting below hypandrial complex (see Fig. 8 , cs). Aedeagal complex ( Fig. 22 ). Phallapodeme relatively robust, having basal part with peculiar (symmetrical) wing-like but ventrally somewhat bent lobes ( Fig. 19 ) embracing basal part of distiphallus (see Fig. 22 ), apex distinctly widened and lateroventrally projecting; fulcrum also relatively robust. Aedeagus of ancestrally looking type ( Fig. 22 ). Phallophore relatively long, subtriangular in profile, darkest on dorsal corner, with posterior corner more projecting and slightly bent ventrally. Distiphallus composed of short but relatively voluminous saccus and long slender filum. Saccus largely membranous except some sclerotization in basal and middle part, and provided with numerous fine spines, mostly on right side of distal membranous part (see Fig. 22 ). Filum of distiphallus ( Fig. 22 ) very slender, formed by 2 dark stripe-like twisted sclerites being attenuated distally but (unlike all other taxa) one of them shortened (ending far from end of filum), and the other terminating in slightly dilated and flattened submembranous apex (see Fig. 21 ). Ejacapodeme relatively small, with slender finger-like projection ( Figs 20, 22 ).

Female. Similar to male but differing as follows. Total body length 3.14 mm. Face and clypeus somewhat darker; antenna distinctly darker, ochreous including 1st flagellomere and arista with somewhat longer cilia. Very unusually f 1 and f 3 (see Figs 26, 27 ) with combs of shortened thicker setae as in male. t 2 with ventroapical seta somewhat longer and thicker. Wing measurements: length 3.02 mm, width 0.87 mm, Cs 3: Cs 4 = 2.04, r-m\ dm-cu: dm-cu = 4.00. Abdomen very elongate (slender) as in male, about 4.5 times as long as its maximum width but having preabdominal terga shorter, slightly more transverse; also preabdominal sterna somewhat wider. T1–T3 becoming wider posteriorly, T3 largest and widest; T4 slightly and T5 distinctly narrower and shorter than T3. S1 and S2 as in male but S3–S5 subequal in length and width, all longer than wide.

Postabdomen ( Figs 23–25 ) relatively long. T6 large (but smaller than T5), distinctly wider and much longer than T7 ( Fig. 23 ), slightly tapering posteriorly, with numerous dense, short setae in posterior two-thirds, darker laterally than dorsally and with narrow pale anterior margin. S6 ( Fig. 25 ) distinctly shorter than S5, about as long as wide, slightly widened posteriorly, all pale whitish ochreous, sparsely setose in posterior two-thirds. T7 ( Figs 23, 24 ) narrower and darker than T6, uniformly blackish brown, densely setose as is T6. S7 much smaller than S6, convex, with rounded sides ( Figs 24, 25 ), with characteristic dark brown pattern leaving only anterior marginal stripe and posteromedial wedge-shaped area pale-pigmented; it is sparsely setose, with longest setae in posterior third of sclerite. T8 relatively flat, transversely suboblong with rounded corners, dark brown except for anterior corners ( Fig. 23 ), with fine but longer setae in posterior third, longest in posterior corners. S8 ( Figs 24, 25 , 28 ) smaller than S7, very convex (bulging posteroventrally, cf. Fig. 24 ), finely setulose, having small posteromedial incision (best visible in Fig. 25 ) in pale-pigmented posterior part and peculiar in being fused with internal sclerites of female genital chamber situated anterodorsally to S8. Internal sclerotization of genital chamber very conspicuous (see Figs 24, 25 , 28, 30 , is). Posterior sclerotization complex, formed by 1 pair of lighter bent anterior sclerites which are posteriorly fused to heavily sclerotized and dark-pigmented but symmetrical complex of sclerites projecting posteriorly on each side in 2 processes and being posteroventrally fused with (invaginated parts? of) S8; annular sclerite also unusual, rather simple, forming a transversely ellipsoid ring situated rather far in front of posterior sclerites ( Figs 28, 30 ). Ventral receptacle ( Fig. 28 ) unusually voluminous but weakly sclerotized and pale-pigmented, of slender kidney-shaped form with smooth surface.Accessory gland on relatively short and slender (non-dilated) duct. Spermathecae (1+1) shortly pyriform ( Figs 28, 29 ), blackish brown, each with a few grain-like spines (mainly on narrowed basal part); duct cervix well developed, comparatively long, pigmented; spermathecal duct relatively short (cf. Fig. 28 ). T10 ( Fig. 23 ) relatively large and broad (shorter than wide), of suboblong rounded outline, dark brown in anterior two-thirds, and with a pair of long medial setae beyond middle. S10 ( Figs 24, 25 ) slightly smaller than T10, semicircular, pale brown, micropubescent, with fine setulae at posterior margin. Cerci ( Figs 23–25 ) mediumsized but robust, with abundant fine setae none of which is particularly longer or thicker.

Discussion. This new species is peculiar in many characters (see above under the genus Marshallya ) but in external appearance it is reminiscent of a large and very slender species of Amygdalops . It particularly resembles some Amygdalops species having a brown-darkened annulus on the femora and tibiae, such as those known from the East Palaearctic and Oriental Regions (see ROHÁČEK 2008, 2009). However, it can be easily distinguished from all known species of the latter genus in having the finely ciliate (not pectinate) arista, the dorsally flattened mesonotum, no prs and sa, short pa, f 1 with a comb of short thickened anteroventral setae, f 3 of both sexes(!) with 2 rows (anteroventral and posteroventral) of thickened and shortened setae and wing with distinct costal spine-like setae among fine setulae. The species of the Afrotropical genus Margdalops are also externally similar to M. platythorax , particularly in their ciliate arista and dark wing pattern (cf. ROHÁČEK & BARRACLOUGH 2003) but they differ (even more distinctly than Amygdalops spp.) in cephalic, thoracic and pedal chaetotaxies. The striking genital and postabdominal differences from Amygdalops, Margdalops and species of other genera of Anthomyzidae have been discussed above under the genus Marshallya and need not be repeated here.

Etymology. The name (a Greek noun in apposition) of the new species refers to the strikingly dorsally flattened thorax (mesonotum).

Biology. The type specimens were photographed ( Figs 6, 7 ) and subsequently collected by Steve Marshall on stems in a copse of bamboo ( Poaceae ) (documented by photograph, Fig. 5 ) on Emei Mountain (at about 800–900 m) on 19 May. Because these peculiar anthomyzids were reasonably abundant in this habitat (but only 3 specimens were collected; S. A. Marshall, personal communication, 2018) it is plausible that this bamboo species is the host plant of M. platythorax .

Distribution. Hitherto known only from the type specimens from China (Sichuan).

Figures

Figs 1–7. Marshallya platythorax sp. nov. and its habitat (China: Sichuan). 1 – wing (length ca. 3 mm); 2 – antenna, laterally; 3 – head and thorax, laterodorsally; 4 – detail of C with spine-like setae; 5 – copse of bamboo, habitat and probable host plant in the type locality (with Owen Lonsdale in front of it); 6, 7 – living adults on bamboo stem (body length ca 3.1 mm). Figs 1, 4 based on male paratype, Figs 2, 3 on male holotype. Photos by J. Roháček (1, 4), M. Tkoč (2, 3) and S. A. Marshall (5–7).

Figs 8–13. Marshallya platythorax sp. nov., male paratype (China: Sichuan). 8 – genitalia, laterally; 9 – external genitalia, caudally; 10 – f3 and t3 anteriorly; 11 – medandrium, anteriorly; 12 – apex of gonostylus, anterolaterally (widest extension); 13 – gonostylus, lateroventrally (widest extension). Scales = 0.5 mm (Fig. 10), 0.05 mm (Figs 12, 13), 0.1 mm (others). For abbreviations see p. 37.

Figs 14–22. Marshallya platythorax sp. nov., male paratype (China: Sichuan). 14–15 – hypandrial complex (14 – laterally; 15 – ventrally); 16 – postgonite and associated structures, laterally; 17 – transandrium, caudally; 18 – postgonite, caudally; 19 – phallapodeme, dorsally; 20 – ejacapodeme, different view than in Fig. 22; 21 – apex of filum, sublaterally; 22 – aedeagal complex, laterally. Scales = 0.05 mm (Fig. 16), 0.03 mm (Figs 18, 21), 0.1 mm (others). For abbreviations see p. 37.

Figs 23–27. Marshallya platythorax sp. nov., female paratype (China: Sichuan). 23–25 – postabdomen (23 – dorsally; 24 – laterally; 25 – ventrally); 26 – female f3, anteriorly; 27 – female f1, anteriorly. Scales = 0.2 mm. For abbreviations see p. 37.

Figs 28–30. Marshallya platythorax sp. nov., female paratype (China: Sichuan). 28 – genital chamber with 8th abdominal segment, laterally; 29 – spermathecae; 30 – internal sclerites of genital chamber and S8 (with setosity omitted), ventrally. Scales = 0.05 mm (Fig. 29) and 0.1 mm (others). For abbreviations see p. 37.