Diacanthomyia Saigusa

Saigusa, Toyohei, 2015, A new genus and species of the subtribe Thyreophorina (Diptera, Piophilidae) from Japan, Zootaxa 4059 (2), pp. 319-334 : 321-325

Diacanthomyia Saigusa , gen. nov.

(Japanese name: Futatoge-bae zoku)

Type species: Diacanthomyia okidoi Saigusa , sp. nov. (Japanese name: Ôkido-futatoge-bae)

Diagnosis. Densely pollinose and partly pruinose Scathophaga -like fly with long pilose legs. Head with 2 strong reclinate fronto-orbital and 1–2 strong subvibrissal bristles. Prosternum setose. One presutural dorsocentral and 2 postsutural intra-alar bristles strong and prominent. Scutellum without additional setae except for pair of apical and lateral bristles. Wing almost entirely microtrichose, marked with a prominent brown round spot on r-m crossvein and a dark stripe covering m-m crossvein; vein CuA+CuP not tapering apically to tip, ending distant from wing margin.

Description. Male ( Figs 1 A, B, D, E). Head, thorax and abdomen densely pollinose and partly pruinose. Head ( Figs 2 A–C) roughly triangular in profile, dorsal surface rather flat and horizontal, supra-antennal area produced forwards; face inclined posteroventrally and with large, shallow oval membranous antennal groove divided medially by narrow flat facial carina, not raised; occipital area moderately produced posteriorly; buccal margin oblique to body axis. Frons 1/2 as wide as head and sparsely clothed with fine hairs, bearing row of several to 10 strong setae along anterior submargin close to lunule. Two pairs of strong reclinate fronto-orbital bristles, anterior one slightly lateroclinate. Proclinate ocellar bristles strong, weakly divergent, arising from lateral to anterior ocellus and in front of lateral ocelli; inner verticals very strong, more or less convergent, outer verticals weaker than inner and divergent; postvertical bristles strong, reclinate and divergent. Compound eye moderately large and oval, with horizontal diameter as long as or slightly longer than 1/2 length of head, longest axis directed anteroventrally. Two strong vibrissae and 1–2 (usually 2) subvibrissal bristles, almost as strong as vibrissae and situated posterior or posteroventral to them. Gena deep, almost as deep as or somewhat less than vertical diameter of compound eye, densely clothed with hairs longer towards buccal margin and occipital area; occipital area clothed with shorter hairs except for wide bare dorsomedian part; row of stiff supracervical setae present. Antenna porrect, about 1/2 as long as depth of head; scape small, with some setulae on dorsal surface; pedicel slightly longer than scape, conical, widened apically, more or less densely setulose, with strong dorsal bristle near distal margin; 1st flagellomere oval and swollen (much flattened in dried specimens), 1.5 times as long as thick or 2 times as long as pedicel; arista 2.4 times as long as 1st flagellomere, bare; more or less thick on 1st and 2nd aristomeres and basal part of 3rd aristomere 2 times as long as 1st and 2nd aristomeres combined. Mouthparts moderately large; maxillary palpus of ordinary length of subtribe, with basal 1/3 slender, distal 2/3 long oval and rather densely clothed with long setae; prementum heavily sclerotized.

Thorax ( Figs 2 D, F). Prosternum with some longish setae along lateral margins; postpronotum only clothed with long hairs in larger males, mixing 1–2 outstanding setae in smaller males. Mesonotum densely pollinose, almost evenly clothed with short hairs longer towards lateral margins and bearing following bristles: 1 weak prescutellar acrostichal bristle, 1 strong presutural and 3 strong postsutural dorsocentral bristles; 1 weak posterior notopleural bristle (smaller specimens also with 1 weak anterior notopleural), 1 strong supra-alar bristle, 1 very strong presutural and 2 strong postsutural intra-alar bristles (anterior postsutural intra-alar bristle situated posterodorsal to supra-alar); 1 strong postalar bristle just anterolateral to posterior postsutural intra-alar. Scutellum elongate, with posterior area lamellate and produced posterodorsally ( Figs 1 D, E), 0.35 (smallest males) – 0.54 (largest males) times as long as scutum, evenly tapered posteriorly (in small males) or tapered to middle, then weakly dilated posteriorly (in large males), with wide, straight posterior margin, lateral corners weakly produced to tubercle-like sockets for apical scutellars. Scutellum bearing pair of extremely long, thick, spine-like apical scutellar bristles from posterolateral corners and pair of shorter, weaker lateral scutellar bristles from lateral margins anterior to middle; no secondary setulae on scutellum. Proepisternum (= propleuron in McAlpine (1977)) clothed with some hairs along ventral margin, mixing with stronger seta; mesepisternum clothed with longish hairs; mesanepisternum with 1–3 stronger setae or bristles along posterior margin; mesokatepisternum sometimes with stronger seta at posterodorsal corner; mesanepimeron bare.

Wing ( Figs 3 A, C–F) rather elongate, clear, with distinct dark round spot on r-m crossvein ( Fig. 3 C) and dark stripe covering m-m crossvein (discal crossvein; Fig. 3 D); wing membrane ( Fig. 3 G of female) including alula almost entirely microtrichose, except microtrichia-free on anterior part of cell cua (traditional cell cup or anal cell), basal part of 2nd basal cell, and posterior part of extremely basal portion (proximal to humeral crossvein) of 1st basal cell. Costa bearing 1 to several spinules only in some large-sized male specimens ( Fig. 3 E); discal cell elongate, with posterodistal corner close to wing margin, with free section of vein M4 (traditional CuA1) shorter than 1/2 of m-m crossvein; vein CuA+CuP (traditional CuA2+A1) reaching to 3/5 way to wing margin, not gradually tapered apically, abruptly ending as thick tip ( Fig. 3 G of female). Halter yellowish white.

Legs extensively pollinose and long haired; hairs of larger males longer, denser and often frizzled apically. Femora swollen, tapered to both ends; hind femur with smooth ventral surface; hind tibia almost straight, slightly curved ventrally in large males. Femora densely clothed with long hairs except on anterior surface of fore femur and posterior surface of mid and hind femora; femora bearing erect, fine, long ventral seta close to base, usually distinguishable from other ventral hairs; no distinct bristles on femora except usually some more or less stiff anteroventral setae of hind femur in smaller males towards apex, and several stronger subapical hairs or setae on posterior surface of mid femur. Tibiae clothed with long hairs except on ventral surface; most hairs in larger males more frizzled apically; mid tibia with 4 (sometimes 3) strong spines beneath at tip, 2nd and 4th spines (counted from anterior one) much stronger than others and in larger males curved dorsally; hind tibia beneath with apical spine. Fore and hind tarsi rather thick, mid tarsus slender; hind metatarsus weakly curved ventrally. Tarsi long haired dorsally; hind metatarsus with some stiff setae beneath towards base.

Abdomen slightly longer than thorax excluding elongated part of scutellum, subbasally almost as wide as thorax, gradually and slightly tapered to bluntly ended abdominal tergum 5; terga more or less flattened dorsally, densely pollinose leaving narrow polished areas along posterior margin. Abdominal terga densely clothed with long hairs, denser in larger males, those on posterior terga frizzy apically. Abdominal sterna pollinose and clothed with hairs shorter than those on terga. Male genitalia ( Figs 4 A, B): Basic structure as in other genera ( Centrophlebomyia , Protothyreophora , Thyreophora ) of the subtribe. Epandrium ( Figs 4 C, D) moderately broad; hypandrium broad, weakly convex. Slender, long aedeagal apodeme fused with hypandrium along ventromedian line and weakly curved ventrally ( Fig. 5 A). Surstylus ( Figs 4 C, D) broad, loosely connected with epandrium, almost quadrate, convex dorsally, with distal margin truncate and curved dorsally; cercus very small, bearing 1 very long and 1 (sometimes 2) shorter setae. Pregonite ( Fig. 5 D) short with several setulae apically; postgonite ( Fig. 5 D) consisting of slender basal and apical sclerites; basal sclerite projecting posteriorly parallel to epiphallus and ending in blunt apex, apical sclerite ventrally bent and closely connected with basal sclerite subbasally; apical sclerite almost as long as basal sclerite, bearing some minute setulae apically and closely approached to apex of pregonite. Spinus (epiphallus; Figs 5 A, C) well developed, slightly shorter than surstylus, more or less spatulate when viewed from above and weakly incised distally; short, basal spine-like process arising from dorsal surface of spinus; basiphallus and distiphallus ( Figs 4 B, 5B) almost as in other genera of subtribe with more or less swollen grans ( Fig. 5 E).

Female ( Fig. 1 C). Similar to male, but hairs on body and legs sparser and shorter. Scutellum ( Fig. 2 E) shorter, 1/3 as long as scutum, 1/3–3/4 as long as wide, with slender but long apical scutellar bristles. Thoracic chaetotaxy almost as in male, but postpronotum usually with 1–2 divergent bristles; anterior notopleural bristle almost always present; 1 propleural, 2–3 mesanepisternal, 1 mesokatepisternal bristle usually distinct; in some specimens 1 additional weak presutural dorsocentral bristle present in front of usual presutural dorsocentral. Hairs on legs shorter and sparser as in small males, hind femur usually with 1–3 stronger anteroventral setae towards apex. Wings ( Figs 3 B, G) and halter as in male.

Abdominal terga with slightly wider posterior marginal and lateral polished areas and shorter, sparser vestiture; tergum 6 evenly and thinly pollinose; abdominal dorsum posterior to abdominal segment 6 polished; abdominal sterna evenly pollinose. Abdominal tergum 6 slightly longer than 5, bearing long posterior marginal setae about twice as long as tergum and shorter lateral marginal setae. Posterior part of abdomen distal to segment 6 more or less telescoped as terminalia.

Female terminalia ( Figs 6 , 7 ): Abdominal segment 7 (= oviscape in McAlpine (1977, figs 23, 24)) consisting of main part of tergum and sternum and two pairs of slender posterior extension sclerites; main part nearly twice as long as segment 6; tergum 7 ( Fig. 6 A) bearing long setae lateral to sublateral areas towards posterior margin; sternum 7 ( Fig. 6 B) produced anteriorly into short triangular extension, and evenly clothed with longish setae on posterior 3/4; abdominal spiracle 7 situated anterior 1/3 of pleural membrane. Posterior extension of segment 7 consisting of each pair of longitudinally slender dorsal (tergal) and ventral (sternal) stripes 1.5 times as long as main part of tergum 7, continuous from posterior margins of main tergum and sternum, respectively; dorsal stripe bearing 3–4 long setae arranged longitudinally; ventral stripe bearing 3 long setae; anterior seta of both stripes longest and strong, posterior seta more or less shorter than anterior one. Abdominal segment 8 ( Figs 7 C, D; shaft in McAlpine (1977, figs 23, 24)) slenderer than posterior extensions of segment 7 and as long as latter; tergum and sternum each divided longitudinally into pair of slender sclerites somewhat similar to posteriorly extended stripes of segment 7; each sclerite tapered anteriorly, slightly widening posteriorly, with several minute setulae. Distal abdominal sclerite ( Figs 7 C, D, E; aculeus of McAlpine (1977, figs 23, 24)) presumably composite sclerite consisting of epiproct, hypoproct and cerci, represented by slender, more or less flattened sclerite slightly curved ventrally, 1/3 as long as 8th abdominal sclerites and 3 times as long as wide, apically with pair of small lateral membranous spots; distal sclerite ( Fig. 7 E) bearing pair of short setulae from subdorsal part of anterior submarginal area (presumably epiproct), and each pair of subdorsal and lateral short setulae (presumably from original cercus) on apical membranous spots.

Etymology. The generic name is feminine and based on the two strong spine-like bristles on the male scutellum.

Figures

FIGURE 1. Diacanthomyia okidoi sp. nov. A, B, D, E: male; C: female. A: holotype, one of largest males; B: paratype, one of smallest males; C: paratype, one of largest females; D: paratype, dorsolateral aspect; E: paratype, lateral aspect.

FIGURE 2. Diacanthomyia okidoi sp. nov. A: male head, anterior aspect; B: ditto, lateral aspect; C: ditto, dorsal aspect; D: male thorax, dorsal aspect (white circle is head of pin); E: female thorax dorsal aspect; F: male head and thorax, anterodorsal aspect showing pair of whitish pruinose spots at mesal extremity of transverse sutures.

FIGURE 3. Wing of Diacanthomyia okidoi sp. nov. A: male wing; B: female wing; C: area around r-m crossvein of male wing; D: area around m-m crossvein of male wing; E: part of costa with spinules of male wing; F: part of costa without spinules of male wing; G: basal part of female wing.

FIGURE 4. Male genitalia of Diacanthomyia okidoi sp. nov. A: lateral aspect; B: posterior aspect excluding epandrium, cerci and surstyli; C: epandrium, cercus and surstylus, lateral aspect; D: ditto dorsal aspect.

FIGURE 5. Male genitalia of Diacanthomyia okidoi sp. nov. A-C: genitalia excluding epandrium and surstyli. A: lateral aspect; B: posterior aspect; C: dorsal aspect; D: posterior aspect of pregonite and postgonite; E: glans of phallus.

FIGURE 6. Female terminalia of Diacanthomyia okidoi sp. nov. A: 7 th abdominal tergum; B: 7 th abdominal sternum; C: terminalia telescoped, lateral aspect.

FIGURE 7. Female terminalia of Diacanthomyia okidoi sp. nov. A: terminalia extended, lateral aspect; B: ditto, dorsal aspect; D: ditto, lateral aspect; E: aculeus and apical part of 8 th abdominal segment, dorsal aspect.