Stenomicra cogani Irwin, 1982

Roháček, Jindřich, 2011, Taxonomy of Stenomicra cogani, with description of S. gracilior sp. nov. from Turkey and comparative morphology of terminalia in Stenomicridae (Diptera), Acta Entomologica Musei Nationalis Pragae 51 (2), pp. 697-722 : 700-708

Stenomicra cogani Irwin, 1982

( Figs. 1–5 , 7–20 )

Stenomicra cogani Irwin, 1982: 235 (description); MERZ & ROHÁČEK (2005): 521, 536 (key, records); ROHÁČEK (2009): 4 (biology, distribution).

Type material. HOLOTYPE: J, GREAT BRITAIN: WALES: Anglesey, Llanfflewyn, Grid.Ref. 23/353891, 11.vii.1976, swept from vegetation beside a small lake, A. Irwin leg. PARATYPES: 3 JJ, with same data as for holotype, all deposited in BMNH (not examined).

Material examined. GREAT BRITAIN: ENGLAND: Norfolk, Surlingham Church Marsh, TG 308 070, 21.vi.2009, 4 JJ 2 ♀♀, C. M. Drake leg. ( CDAG, in ethanol). ITALY: Mantova pr. Marmirolo, Bosco d. Fontana, 50 m, 42.12 N, 10.45 E, 20.v.2001, 2 JJ 1♀, Merz & Mason leg.( SMOC). CZECH REPUBLIC: N BOHEMIA: Sosnová 1.5 km SW, Peklo reserve, 50°39′N, 14°31′E, sweeping Carex acutiformis in alder forest, 27.vi.2008, 2 JJ; Pavlovice 2 km W, Dolské údolí (valley), 50°36′N, 14°30′E, sweeping Scirpus sylvaticus in boggy meadow, 25.vi.2008, 1J 2 ♀♀; Doksy env., Břehyňský rybník (pond) reserve, 50°35′N, 14°43′E, sweeping Carex acuta in boggy meadow, 24.vi.2008, 2♀♀; Hradčany 1.5– 2 km W, Ploučnice valley, 50°37′N, 14°41′E, sweeping Carex rostrata in boggy meadow, 23.vi.2008, 1 J 2 ♀♀, sweeping Carex rostrata in boggy meadow, 26.vi.2008, 1 J; Višňová, Meandry Smědé res., 50°59′06″N, 15°01′38″E, 225 m,sweeping Carex nigra in boggy meadow, 14.vi.2011, 1J 2♀♀; Černousy,Dubák pond, 50°59′54″N, 15°02′32″E, 230 m, sweeping Scirpus sylvaticus in alder forest, 16.vi.2011, 7 JJ 13 ♀♀, all J. Roháček leg. ( SMOC). S BOHEMIA: Vráž nr. Písek, 49°24′12″N, 14°7′13″E, 430 m, damp meadow, 18.–22.vii.2007, 1 J, M. Barták leg. ( MBPC). N MORAVIA: Polanka nad Odrou, Přemyšov reserve, 49°47′N, 18°11′E, sweeping Carex acuta in boggy meadow, 16.vii.2008, 2 ♀♀, sweeping Carex vesicaria in boggy meadow, 16.vii.2008, 1 J 1 ♀, sweeping Scirpus sylvaticus in boggy meadow, 16.vii.2008, 1 J 1 ♀; same locality, reared ex tussock of Scirpus sylvaticus collected in boggy meadow 11.vii.2009 – 1 J 1 ♀, emerged 11.v.–9.vi.2009 and 1 J emerged 9.vi.–9.vii.2009, reared ex tussock of Carex elongata collected in boggy meadow 11.v.2009 – 1 ♀ emerged 9.vi.–9.vii.2009; Šilheřovice, Černý les res., 49°54′25″N, 18°16′31″E, 240 m, reared ex tusocks of Scirpus sylvaticus collected at forest creek 9.vi.2010 – 4JJ 1 ♀ emerged 9.–24.vi.2010, 1 ♀ emerged 24.vi. –28.vii.2010. SW MORAVIA: Třešť 1 km E, Lávecká cesta (distr. Jihlava), sweeping Scirpus sylvaticus in boggy meadow, 5.viii.2005, 1 ♀, 11.viii.2005, 1J. S MORAVIA: Hrabětice,Trávní Dvůr 1 km SW, 48°47′N, 16°26′E, sweeping Carex sp. in floodplain forest, 18.v.2009, 1 J, sweeping Carex vesicaria in boggy meadow, 7.vii.2009, 2 JJ 3 ♀♀, all J. Roháček leg. ( SMOC). ROMANIA: BANAT: Gornea nr. Sicheviţa 1 km S, Gornea river valley, 73 m, 44°39′51″N, 21°51′39″E, sweeping Carex acuta in boggy meadow, 4.vi.2008, 3 JJ, J. Roháček leg. ( SMOC). A number of specimens with genitalia prepared.

Diagnosis. A small, slender, largely yellow species ( Figs. 1–3 ) with posterior cross-vein (dmcu) absent. It differs from the only other Stenomicra species lacking dm-cu, viz. S. gracilior sp. nov. (described below), by generally paler colouring and setae, 5–6 ac setulae, male mid femur with anteroventral row of 7–8 setae, smaller brownish spots on female abdominal terga T2, T3–T5 and by other characters (including those in male and female terminalia) listed below in the diagnosis of S. gracilior sp. nov.

Redescription. Male. Total body length 1.36–1.81 mm. General colour yellow to pale yellow (head with frons and occiput yellowish white), only small ocellar triangle dark reddish brown, thorax dorsally and some parts of its pleura sometimes with faint pale brown darkening and abdomen with 3 rd –4 th segments usually appearing reddish brown due to internal colouration (best visible on living specimens – see Fig. 3 ).

Head subtriangular in profile ( Fig. 4 ), with face strongly protruding in front of anteroventral eye margin, yellow but yellowish white and whitish microtomentose on frons (lightest posteriorly) and on occiput. Compound eye diagonal, elongately reniform (its longest diameter about 2.3 times as long as shortest) and exposing a large area of occiput at side of head, dark reddish brown (red when alive), with facets slightly larger in dorsal half and with whitish interfacetal microsetulae. Frons largely bare, wide, parallel-sided, almost square (1.05–1.10 times as high as wide), flat, medially (particularly anteriorly) somewhat depressed, yellowish white and microtomentose; ocellar triangle small, dark red to brown, slightly raised, situated in the middle of frons; ocelli relatively small. Face darker yellow than frons, slightly carinate and with shallow concavities below antennae, narrowing ventrally and strongly produced above mouthedge. Facial sensilla (medially above pseudovibrissa) reduced, poorly visible (in contrast to those in Podocera species , cf. MERZ & ROHÁČEK 2005: Figs. 13–14 ). Antennae yellow, somewhat divergent; pedicel relatively large, expanded on inner side and so partly covering base of 1 st flagellomere (postpedicel) and bearing a few proclinate setae dorsally subapically; 1 st flagellomere with a fringe of long white hairs on tip; arista brown, slightly longer than antenna, long-pectinate (longest rays longer than 1 st flagellomere), dorsally with 4–5, ventrally with 2 rays in addition to apical fork. Mouthparts yellow, small, with palpus strongly reduced, bare, poorly visible.

Chaetotaxy. Cephalic setae and setulae largely yellow, at most tips of major setae brown; 2 ors in anterior half of frons – 1 strong and long posterior and 1 short (half length of the former) anterior, both slightly reclinate; 1 long, slightly lateroclinate vte; 1 slightly shorter, proclinate vti (= pseudopostocellar of MERZ & ROHÁČEK 2005); posteromedially of the latter with 1 short, upright, slightly divergent pvt (= postocellar) on dorsal margin of occiput; no oc seta; 1 strong, porrect, somewhat lateroclinate pseudovibrissa (pv), inserted on ventral side of ‘vibrissal’ angle; posteriorly of it with 1 short, proclinate setula and with a series of 6–7 ventroclinate peristomal (per in Figs. 21, 22 ; genal of MERZ & ROHÁČEK 2005) setae, becoming shorter posteriorly. On the boundary of gena and occiput, near posteroventral eye margin there is 1 strong (genal) upcurved seta (cf. Fig. 22 ); posteroventral angle of occiput with a few small setulae; postoculars reduced to only 1–2 setulae behind posterodorsal margin of eye.

Thorax slender, somewhat narrower than head, yellow with sparse pale grey microtomentum, but its dorsum (scutum, scutellum and subscutellum) sometimes with pale brownish tinge, also anepisternum, anepimeron and meron can be partly slightly darkened. Entire metanotum darker brown (up to base of haltere). Scutellum triangular, slightly wider than long, convex; subscutellum bulging.

Chaetotaxy. All setae yellow to ochreous; 5–6 ac setulae, in single irregular row which may be doubled in front of suture (in this case up to 9 acrostichals are present), ending at most behind the level of anterior dc macroseta; 2 strong postsutural dc, the anterior about two-thirds of the more robust posterior, 4–5 dc setulae in front of them but no setulae in large gap between them; no hu (postpronotal) seta but 3–4 posthumeral setulae and 1–2 setulae also between them and foremost dc setulae; 2 stronger subequal npl; 1 short pa; no intraalar seta, only a few (usually 2–3) setulae; scutellum with only 1 long apical sc (as long as posterior dorsocentral seta); 1 long katepisternal seta and several (more than 5) short setae on ventral portion of katepisternum.

Wing ( Fig. 5 ) relatively long and narrow, with whitish membrane and yellowish white veins. C reaching to apex of R 4+5, with single costal break in front of apex of R 1. Sc short, ending free in subcostal cell. R 2+3 slightly sinuate, ending far from apex of R 4+5, the latter basally straight, apically slightly recurved and terminating in wing apex. M slightly but distinctly bent forward, strongly convergent with R 4+5 distally and ending close to it. CuA 1 almost straight, not reaching wing margin. Cross-vein r-m present, removed less than one-third from wing base; cross-vein dm-cu absent.A 1 reduced, very short, not reaching wing margin.Alula absent. Posterior wing margin with relatively long ciliation. Wing measurements: length 1.62–1.95 mm, width 0.49–0.85 mm, Cs 3: Cs 4 = 6.00–7.63. Haltere pale yellow.

Legs yellow with yellow setosity, only last tarsal segment of fore and mid leg brownish. Fore femur (f 1) with a series of 5–7 posteroventral long and thicker setae (the longest situated in distal third slightly longer than maximum width of femur) and with a row of 7–8 shorter and finer posterodorsal setae (longest in proximal third of femur); f 2 with anteroventral row of 7–8 finer setae (longest about two-thirds width of femur); t 2 with ventroapical seta (distinctly longer than maximum width of tibia); legs otherwise uniformly setulose but setae on femora relatively long.

Abdomen long and slender, with all sclerites yellow (3 rd and 4 th segments seemingly dark in living and dried specimens due to internal colouration, see Fig. 3 ). T1+2 long, longer than T3 or T4, with boundary between T1 and T2 poorly delimited. T3–T5 relatively long but distinctly transverse (wider than long) and becoming narrower posteriorly. All preabdominal terga with sparse short yellow setae on lateral and posterior margins. Preabdominal sterna S2–S5 large (hence pleural membrane between terga and sterna small), pale yellow; S1 short (about one-fourth of length of S3), transverse, as wide as S2 anteriorly; S2–S5 very slightly transverse, becoming somewhat smaller posteriorly but all of similar shape and with scatered short setosity. Abdominal spiracles reduced, hardly visible. Postabdomen: T6 well developed although short and transverse (about 3 times wider than long), almost as wide as T5, with a row of short setae on posterior margin. S6–S8 (see Fig. 10 ) fused to relatively symmetrical ring-shaped complex; its ventral medial crescent-shaped plate (original S6) almost symmetrical (most asymmetrical case in Fig. 11 ), posteromedially more or less projecting and with denticulate margin ( Figs. 11, 12 ).

Genitalia. Epandrium ( Figs. 7, 8, 10 ) yellow, slightly higher than long, as broad as high ( Fig. 7 ), uniformly, relatively densely and shortly setose and with 1 (rarely 2) setae near middle of each ventrolateral margin. Anal fissure small and narrow, and its membrane gradually transient in epandrial sclerites. Cerci small, closely attached but extended inside epandrial capsule (thus long), setose not only posteriorly but also ventrally ( Fig. 8 ). Gonostylus ( Figs. 7–9 ) strongly bent inside (inclined) and often poorly visible in lateral view (it is somewhat unnaturally straightened in Fig. 8 to show its insertion); in widest extension view ( Fig. 9 ) with flat, dilated and anteriorly setose (5–6 setae) proximal third, and slender, strongly curved remaining distal part being characteristically wrinkled in concavity, micropubescent posterodorsally and bearing 4–5 short setae on the rounded and darkened apex. Medandrium (subepandrial sclerite, bacilliform sclerite) reduced to 2 slender, medially (under cerci) connected sclerites, each with 1 distinct seta and attached to posterior margin of epandrium ( Fig. 7 ). Hypandrium ( Figs. 8, 10, 13 ) formed as rather asymmetrical frame-like structure, posteriorly open, anteriorly without apodeme, integrating posteroventral asymmetrical appendages (pregonites) projecting ventrally and bearing 2–3 (3 on left side) long setae dorsally. Aedeagal complex ( Fig. 13 ) also asymmetrical, lacking postgonites. Phallophore poorly visible, short, probably crescentshaped and widely connected with voluminous but short distiphallus. Distiphallus composed of large membranous part (saccus) with striated surface (mainly posteriorly and ventrally) and of slender, sclerotized, relatively short tubular structure (filum) having membranous forked apex ( Fig. 14 ). Phallapodeme ( Fig. 13 ) relatively short but robust, with simple anterior rod and extended basal part projecting ventrally. Ejacapodeme ( Fig. 8 ) free, rather large, as long as phallapodeme, rod-like but proximally somewhat thickened.

Female (newly described). Similar to male unless mentioned otherwise. Total body length 1.58–2.06 mm. Somewhat darker, with abdomen laterally spotted ( Figs. 1, 2 ) and all setae distinctly darker, setulae ochreous, macrosetae usually brown. Face with distinct brown U-shaped line bordering parafacialia. Fore femur with somewhat longer setae in posterodorsal row; mid femur uniformly setulose, without anteroventral row of longer setae. Wing measurements: length 1.92–2.26 mm, width 0.56–0.67 mm, Cs 3: Cs 4 = 6.04–7.57. Abdomen ( Figs. 15, 16 ) with preabdominal sclerites yellow to pale yellow except for T2, T3 and T4 having distinct brown lateral spots (see also Fig. 1 ). T1 coalesced with T2 and this syntergum markedly longer than T3. T3–T5 becoming slightly narrower posteriorly but all of similar shape. T1 with small setulae medially, T2–T5 with short setae in front of posterior margin and a few longer laterally. S1 smallest preabdominal sternum, almost bare; S2 and S4 subtrapezoidal (narrower anteriorly), S3 narrow and long (longest sternum) and S5 widest, transversely oblong. S2–S5 with short scattered setae. Spiracles 2–5 very small and poorly visible, situated below lateral margin of relevant terga.

Postabdomen ( Figs. 19, 20 ). T6 normal, yellow, transversely oblong, with a row of short setae in front of posterior margin. T7, S6 and S7 forming a peculiar tergosternal ring, dark pigmented dorsally (two basal thirds) and laterally, armed by a conspicuous ventrolateral digitiform projection on each side (obviously a part of the original S6). Dorsal part (= T7) of this tergosternum with sparse longer setae; ventral part with two series of denser setae, one at original posterior margin of former S6, the other on posterior margin of original S7. 6 th spiracle situated laterally, in part belonging to original S6. T8 and S8 also coalesced, forming a short tergosternal ring but only its dorsal part (= T8) longer, pale brown pigmented and setose ( Fig. 19 ); its ventral part (= S8) reduced to very short, transverse, bare, unpigmented (and poorly visible) strip ( Fig. 20 ). Genital chamber membranous, without sclerotized structures; ventral receptacle ( Fig. 17 ) also membranous, vesiculate, distally somewhat widened and with rugged surface. Spermathecae (1+1) black, heavily sclerotized (visible through pale abdominal sclerites also in dry specimens), roughly globular but large distal part with plain surface while its proximal part, separated by fine ledge-like line, formed by 5–6 bulges surrounding insertion of spermathecal duct ( Fig. 18 ); the latter relatively short (see Fig. 17 ) and provided with palepigmented distal collar being about half length of spermathecal body. T10 (supra-anal plate) extremely reduced, hardly recognizable, forming small to minute subtriangular unpigmented plate with 2 microsetulae in the middle ( Fig. 19 ). S10 (subanal plate), on the contrary, large, trapezoidal, pale-pigmented, covered by dense and long micropubescence and with 2–3 lateral setae. Cercus ( Figs. 15, 19 ) subconical but dorsoventrally somewhat flattened, relatively short and robust, with short setae (apical longest) and fine micropubescence.

Discussion. The species is redesribed here on the basis of specimens from Great Britain, Italy, Czech Republic and Romania (thus from most of its known distribution range) to recognize the variability of adult characters. However, it was found that the geographical variability is not larger than variability recorded within the single population from the locality Černousy, Dubák pond (CZ: N Bohemia) where the largest sample (20 specimens) was available for study. This knowledge enabled true differences from S. gracilior sp. nov. from Turkey to be revealed. The study of the female abdomen (postabdomen in particular) resulted in finding of additional structural differences supporting the validity of the new species.

Biology. The knowledge of habitat and host plant association was summarized in detail by ROHÁČEK (2009). The additional material obtained since this study confirmed preference of S. cogani for Scirpus sylvaticus L. growths in swampy habitats, including a series of 20 adults collected (2011) and 5 additional specimens reared (2010) from tussocks of this sedge. There is also a new collecting record (2011) of the species from Carex nigra (L.) Reichard which again demonstrates that the species can also live in stands of various large Carex species as already found by British dipterists (e.g. DRAKE 2004), for more detail see ROHÁČEK (2009). Adult occur in May to August.

Distribution. The species is probably widespread in Europe. Hitherto, it has been recorded from southern Spain, northern Italy, Ireland, Great Britain ( Wales, England), northern Germany, southern Sweden, Czech Republic ( Bohemia, Moravia) and southwestern Romania (Banat), for more detail, relevant references and distribution map see ROHÁČEK (2009).

Figures

Figs. 1–4. Stenomicra cogani Irwin, 1982 (Czech Republic: N Bohemia). 1 – female (body length ca. 2 mm) sitting on leaf of Scirpus sylvaticus; 2 – same, dorsal view; 3 – male (body length ca. 1.5 mm) on the same leaf; 4 – male, head and thorax laterally (from dry mounted specimen). Photo by J. Roháček (Figs. 1–3) and M. Deml (Fig. 4).

Figs. 5–6. Wings of Stenomicra species. 5 – Stenomicra cogani Irwin, 1982, female (Czech Republic: N. Bohemia), length 1.95 mm; 6 – S. gracilior sp. nov., male (holotype), length 1.63 mm. Photo by J. Roháček.

Figs. 7–14.Stenomicra cogani Irwin, 1982, male. 7 – external genitalia, caudally; 8 – genitalia, laterally; 9 – gonostylus, subventrally, widest extension; 10 – genitalia and pregenital synsternum S6–S8 in situ, ventrally; 11 – part with original S6, ventrally; 12 – same, another variant; 13 – internal genitalia, laterally (with ea omitted); 14 – filum of distiphallus,anteroventrally.Figs.7, 12 based on specimen from Romania:Banat, others on specimens from England. Scales = 0.1 mm (Figs. 7, 8, 10), and 0.05 mm (Figs. 9, 12–14). For abbreviations see text (p. 701).

Figs. 15–20. Stenomicra cogani Irwin, 1982, female (Czech Republic: N Bohemia). 15 – abdomen dorsally; 16 – same, ventrally; 17 – genital chamber with ventral receptacle and spermatheca, laterally; 18 – spermathecae; 19 – postabdomen, dorsally; 20 – S5 and postabdomen ventrally. Scales = 0.2 mm (Figs. 15, 16), 0.05 mm (Figs. 17, 18) and 0.1 mm (Figs. 19, 20). For abbreviations see text (p. 701).

Figs. 21–23. Stenomicra gracilior sp.nov., male (holotype). 21 – head frontally; 22 – head, laterally; 23 – f2 anteriorly. Scales = 0.2 mm. For abbreviations see text (p. 701).