Switzerland, Canton of Ticino, Municipality of Losone, Forest reserve of “Parco Collina di Maia”, 46°09'53"N, 8°44'54"E, 419 m.

• ♂, pinned, labelled “SVIZZERA – TI; 701.168/113.372; Losone, Arcegno, Collina di Maia; Castagneto con querce; 419 m; 21–28.07.2015, prd. 1; VINO Bianca; ARC 2; Leg: L. Pollini P.& M. Abderhalden; DIPT04008, GBIFCH00559684. [Switzerland, Ticino; Losone, Arcegno, Collina di Maia; chestnut and oak forest; 419 m; 46°09'53"N, 8°44'54"E Wine trap White] (deposited in MCSN).

• 2♂♂; SVIZZERA – TI; Losone, Arcegno, Collina di Maia; Castagneto con querce; 420 m; 701.151/113.376 [46°09'51.337"N, 8°44'53.687"E]; ARC1; 20.05–06.06.2016; Vino Bianca. • 1♂; same, but 23.06–07.07.2016. • 1♂; same, but 701.013/113.741 [46°10'03.240"N, 8°44'47.535"E]; 411 m; ARC2; 20.05–06.06.2016. • 2♂♂ same but 06–23.06.2016; Vino gialla. • 2♂♂ same but, 701.307/113.196 [46°09'45.434"N, 8°45'00.812"E]; 366 m; ARC3; 21–28.07.2015. • 5♂♂ same but 20.05-06.06.2016; Vino Bianca. All L. Pollini & M. Abderhalden leg., all dried from ethanol and pinned (MCSN). • 15♂♂ Losone, Arcegno, Collina di Maia; Castagneto con querce; 411 m; 701.013/113.741 [46°10'03.240"N, 8°44'47.535"E]; ARC2; 06-20.05.2016. • 4 ♂♂; same but 701.307/113.196 [46°09'45.434"N, 8°45'00.812"E]; 366 m; ARC3; 23.06-07.07.2016.; all L. Pollini & M. Abderhalden leg.; all preserved in ethanol (MCSN). • 18♂ (3♂ with genit. prep., 1 intact ♂ photographed) 701.168/113.372; 419 m; ARC2; 13-27.07.2017, prd. 25; Vino bianca. • 2♂ same data but 10-23.08.2017, prd. 27; all L. Pollini & M. Abderhalden leg., all dried from ethanol and 16 mounted on pinned triangular cards, 4 double-pinned (on minutia pin in pinned plastic bricket) (SMOC).

all other specimens from the same locality preserved in ethanol (deposited in MCSN). Same locality, 701.168/113.372, 419 m, ARC2,13–27.07.2017, 13–27.07.2017, prd. 25, vino bianca, 1♂, L. Pollini & M. Abderhalden leg., but with blue label “JR32, OM314931” (handwritten) in addition; specimen used for molecular study, with body (after DNA extraction) preserved in glycerine in pinned plastic vial (SMOC).

A small species (1.3 mm) (Fig. 7) closely resembling Periscelis (Myodris) annulata but with microtomentum of scutum and scutellum (Fig. 4) darker and more brownish, consequently, acrostichal and dorsocentral brown stripes are less contrasting (somewhat resembling mesonotal pattern in P. (M.) piricercus, cf. Fig. 6). Cerci longer and more slender (Figs 11, 12, 14, 24, 35) than those of P. (M.) annulata (Figs 17, 18, 22, 28, 36), with 2 short anteroapical black spines which are short and emerge close to each other; subapical posterior setae hardly longer than other posterior setae (Figs 12, 24). Surstylus more gradually tapering and rather straight distally (Figs 15, 25). Postgonite more elongate, with slender distal part longer and slightly bent (Figs 13, 26).

Figures 4–10. 

Periscelis (Myodris) species, adults. 4. P. (M.) haennii sp. nov., male paratype (dried from ethanol), thorax dorsally; 5. P. (M.) annulata (Fallén), male (dry mounted), thorax dorsally; 6. P. (M.) piricercus Carles-Tolrá & Verdugo Páez, male (dried from ethanol), thorax dorsally; 7. P. (M.) haennii sp. nov., male paratype (dried from ethanol), laterally; 8. P. (M.) haennii sp. nov., male paratype, right wing; 9. P. (M.) annulata (Fallén), male, right wing; 10. P. (M.) piricercus Carles-Tolrá & Verdugo Páez, male, right wing. Only Fig. 5 is based on specimen from Slovakia, others are from specimens from Losone (Switzerland). All scales: 0.5 mm. Photos by J. Roháček.

Figures 11–16. 

Periscelis (Myodris) haennii sp. nov., paratype, male genitalia. 11. Entire genitalia, laterally; 12. Cercus, laterally; 13. Aedeagal complex, laterally (only basal parts of distiphallus, phallapodeme and hypandrium depicted); 14. External genitalia caudally; 15. Surstylus, laterally; 16. External genitalia cranially (setosity of epandrium and cerci largely omitted). For abbreviations see p. 41. Scales: 0.05 mm (12, 15); 0.1 mm (11, 13, 14, 16).

Figures 17–22. 

Periscelis (Myodris) annulata (Fallén), male genitalia (Slovakia). 17. Entire genitalia, laterally; 18. Cercus, laterally; 19. Aedeagal complex, laterally (only basal parts of distiphallus, phallapodeme and hypandrium depicted); 20. External genitalia cranially (setosity of epandrium and cerci largely omitted); 21. Surstylus, laterally; 22. External genitalia caudally. For abbreviations see p. 41. Scales: 0.05 mm (18); 0.1 mm (17, 19–22).

Male (Fig. 7). Total body length (holotype) 1.31 mm, wing length 1.01 mm. General colour mainly brown and grey, microtomentose and dull; some parts of head and legs yellow and abdomen with small silvery white microtomentose spots in lateral margin of tergites. Head: face microtomentose, protruding in front of anteroventral eye margin; mainly brown but yellow ochreous on the concavities below the antennae and on carina. Darkened on the protrusion above mouth edge. Frons large, brown, ocellar triangle small, situated at posterior margin of frons; ocelli arranged in equilateral triangle. Gena relatively low, postgena expanded posteriorly, brown and becoming darker posteriorly, towards concave occiput. Eye margin with a thin yellow ochreous stripe. Clypeus brown, palpi yellow. Antennae divergent and largely yellow, only pedicel with dull black dorsal spot covering completely the outer lateral side and one third of the inner side; pedicel with a row of short setae. Pedicel cap-shaped, relatively large, larger than the first flagellomere; the latter with apex slightly curved upwards, yellow, covered with light short pilosity. Arista yellow, long-pectinate, dorsally with 7 rays (3 longer and 4 shorter), ventrally with 4–5 rays (2 longer and 2–3 shorter). Mouthparts and palpi yellow ochreous, clypeus brown. Cephalic chaetotaxy: all setae blackish brown; pvt well developed, divergent, situated at dorsal margin of occiput behind the inner margin of ocelli; 1 longer convergent and inclinate vti; 1 slightly divergent and lateroclinate vte; 1 reclinate ors, 1 proclinate oc; 3–4 microsetulae in front of ors. No vibrissae or pseudovibrissae but with 3–4 short ventro-reclinate setae on ventral side of vibrissal angle and anterior part of gena; a row of 4–5 pairs of inclinate setae on lateroventral margin of face; gena posteriorly to vibrissal part with a series of 5–6 thicker and longer ventro-clinate peristomal setae, becoming shorter posteriorly; expanded part of postgena and occiput behind eye with numerous short setae being stronger near posteroventral eye margin.

Thorax: dull, brown with a grey microtomentose pattern; mesoscutum grey with brown acrostichal and dorsocentral brown stripes little contrasting compared to the background colouring; pleural part of thorax brown, with an apical paler stripe on the anepisternum; scutellum distinctly (basally) wider than long, rounded trapezoidal.

Thoracic chaetotaxy: all setae and setulae blackish brown; ac setulae numerous and in 8 irregular rows, more numerous in the anterior half of scutum, 2 postsutural strong dc setae, the posterior one longer; 8–10 setulae in front of dc but no setulae between dc setae; 1 prescutellar ac; 1 strong hu (= postpronotal) seta plus 2 small setulae on humeral callus; 2 strong npl setae; 1 sa and 1 pa; 2 sc setae, the apical one very long; 2 stpl (= katepisternal) setae, the anterior one shorter, and numerous short setulae on sternopleuron (katepisternum).

Wing (Fig. 8) closely resembling that of P. annulata, pale brownish, cross-vein r-m and section between r-m and dm-cu cross-veins on M somewhat brown darkened; cells c, r₁, r₂₊₃ light brown shadowed. Haltere light brown.

Legs yellow and brown variegated. Base of fore coxa brown, ventrally apically yellow, coxae 2 and 3 brown. Fore femur dark brown with base yellow. Femora 2 and 3 yellow with two not well bounded brown rings; tibiae with two dark brown rings, the distal one longer than the proximal; tarsi yellow with two last segments brown. Femur 1 with a series of 7–8 long and thicker distal posteroventral setae and other finer upright posterodorsal setae; femur 2 posteroventrally with a row of short and thicker setae; tibia 2 with 1 distinct and thicker ventroapical seta.

Abdomen brown, sternites lighter; tergites 3–6 with a pair of anterolateral small silvery spots. Postabdomen: pregenital sternite (sternite 6) simply transversely suboblong but posteromedially with small and shallow emargination (Fig. 23), generally pale brown but medially narrowly lighter, with setae restricted to posterior half of sclerite. Sternite 6 most resembling that of P. annulata except for all setae generally shorter, including longest lateral setae.

Male genitalia (Figs 11–16) most resembling those of P. (M.) annulata. Epandrium (Figs 11, 14, 16) relatively small, formed as a short arch-shaped sclerite, thus distinctly higher than long (Fig. 11) and about as high as broad (cf. Fig. 14), with large anal opening (fissure). Setosity of epandrium relatively uniform, restricted to its posterior marginal area but (in contrast to that of P. annulata) with some setae also posteroventrolaterally. Anteroventral projection of epandrium (= surstylus) long, proximally broad but distally gradually tapered (not angulate basally anteriorly) and very slender, in distal half with fine setulae at anterior margin (Fig. 15), and with apex somewhat blunt. Cerci relatively free, situated below anal opening as in all other Periscelis species but slender and elongate (longer than in any other known species of the subgenus Myodris), longer than height of anal opening (see Fig. 14). Each cercus (Fig. 12) tapering towards apex, the latter armed by a pair of closely arising robust, short and anteriorly directed spines; posterior and (partly) lateral sides of cercus with long setae and some micropubescence; posterior apical and subapical setae hardly longer than those situated more proximally (see Fig. 12). True gonostylus (as defined by Roháček and Andrade 2017) entirely absent (as in all Myodris species) and medandrium very reduced, forming a poorly visible strip-like sclerite situated posterior to hind part of hypandrium. Hypandrium (Fig. 11) frame-shaped but in contrast to that of Periscelis s. str. species more distinctly separated from phallapodeme (both sclerites only partly fused anteriorly and laterally). No appendages (= pregonites) of hypandrium. Aedeagal complex very large (compared to epandrium) and symmetrical, formed by voluminous phallapodeme, very long aedeagus and paired postgonites. Phallapodeme (Fig. 11) very similar to that of P. (M.) annulata, large, forming a single pocket-shaped (hood-like) capsule, thus with short and forked basal part completely fused to distal capsuliform part (in contrast to construction in Periscelis s. str. species, where these parts are separate, cf. Roháček and Andrade 2017, fig. 6). Aedeagus (Fig. 11) simple (without separate basal part = phallophore, thus formed only by distiphallus), weakly sclerotized to submembranous, forming slender and very long arched ribbon, partly hidden in capsule of phallapodeme; apex of distiphallus slightly widened, terminally blunt, unarmed, membranous. Postgonite (Fig. 13, pg) long and slender, about as long as surstylus (cf. Fig. 11), with short broad basal part and long, slender, slightly bent (often subterminally very slightly sinuate) distal part having subacute apex and series of setulae laterally and at posterior margin. Ejacapodeme (Figs 11, 13, ea) large and robust, relatively simple, basally somewhat wider than distally, longer and more elongate (about 5.5 times as long as its maximum width) than that of P. (M.) annulata.

Based on structures of male genitalia, Periscelis (M.) haennii sp. nov. is clearly different from all known Palaearctic relatives of the subgenus Myodris (cf. diagnosis above and Papp and Withers 2011). Although externally very similar to P. (M.) annulata (and most resembling the latter species also in genital characters) it proved to be distinctly different from both other European (and syntopically occurring) Myodris species in the DNA sequences of the barcoding gene COI (genetic distances are 7.58% from P. (M.) annulata and 9.12% from P. (M.) piricercus, respectively), see Table 1. Thus, not only the morphological characters of the male genitalia but also molecular features demonstrate the validity of this formerly cryptic species; as only one specimen has been barcoded for each species, in this context it is not possible to detect intraspecific variation.

The study of long series of all three European Periscelis (Myodris) species obtained from the same area and habitat revealed the formerly unknown external variability both in thoracic micropubescence and colour pattern, and, particularly, in clouding of wing membrane and veins. The latter was particularly variable in P. (M.) annulata. Based on these findings we found that these three species cannot be safely recognized from only external features and their identification should always be verified by study of male genitalia. Consequently, females of these species cannot be unambiguously recognized at present from morphology. However, they can now be identified by means of the molecular barcoding.

The new species seems to be the closest relative of P. (M.) annulata. The most obvious putative synapomorphy of these two species is the markedly elongated and slender male cercus (being distinctly shorter and basally more dilated in all other species of Myodris, including P. (M.) piricercus and P. (M.) kabuli L. Papp, 1988, see Papp and Withers 2011). However, it is to remark that P. (M.) haennii shares with P. (M.) piricercus similarly closely positioned anteroapical spines on male cercus (cf. Fig. 24 and Fig. 32) but this “feature” also occurs in more distant relatives, viz. in P. (M.) kabuli and even in the Nearctic P. (M.) flinti (Malloch, 1915), cf. Papp and Withers (2011, figs 27, 35). The close relationship of P. (M.) haennii and P. (M.) annulata is also indicated by the elongate (with long slender distal part) postgonite which can be another putative synapomorphy of this species-pair.

Unknown but probably similar to that of P. (M.) annulata which is associated with sap runs on wounded trees, particularly oaks and elms (most often in their crowns) having larvae developing in fermenting tree sap (cf. Papp 1998). The 305 specimens of P. (M.) haennii sp. nov. were collected by means of attractant traps (wine and beer, see Figs 1, 2) in a lowland forest of oaks and chestnuts (Fig. 3). Actually, in these traps also both other Periscelis (Myodris) and two Periscelis (s. str.) species were captured (Pollini Paltrinieri et al., unpublished data).

Hitherto only known from southern Switzerland. However, it can be presupposed that P. (M.) haennii will also be found elsewhere in Europe, particularly in more southern areas simply because it has not been formerly distinguished from P. (M.) annulata.

The specific name is dedicated to the eminent Swiss dipterist and our friend Jean-Paul Haenni.

Epandrium (Figs 17, 20, 22) small, shortly arch-shaped, distinctly higher than long (Fig. 17) but almost as broad as high (Fig. 22), with large (although slightly narrower than that of P. (M.) haennii) anal opening. Setae on epandrium relatively long but subequal in length and distributed only in posterior marginal area surrounding anal opening. Surstylus (Fig. 21) long, proximally broad but relatively suddenly (see somewhat angular anterobasal part) distally tapered. This slender distal part of surstylus slightly bent, provided with a row of fine setulae at anterior margin (Fig. 21) and with relatively acute apex. Cerci free and inserted below anal opening as in relatives. Each cercus slender and elongate but shorter than height of anal opening (see Figs 20, 22), tapered distally, with apex slightly bent anteriorly (Fig. 18) and provided with a pair of distinctly separate short anteroapical spines; posterior and posterolateral sides of cercus with some micropubescence and a row of long setae, the apical and (often) also subapical which are longer than others (see Fig. 18). True gonostylus lost; medandrium (see Fig. 20, ma) extremely reduced, forming a small transverse sclerite attached to posterior part of hypandrium. Hypandrium (Fig. 17) frame-shaped and relatively well separated from (dorsally attached) phallapodeme as characteristic for all Myodris species, without any trace of pregonites. Aedeagal complex very large, composed of large pocket-shaped phallapodeme, very long and slender submembranous aedeagus and distinctly sclerotized paired postgonites. Phallapodeme (Fig. 17) formed as in P. (M.) haennii, thus pocket-shaped and compact (= without separate basal part). Aedeagus (Fig. 17) also very similar (both in form and length, and formed only by distiphallus) to that of the latter species but its membranous apex rather spindle-shaped. Postgonite (Fig. 19) relatively large and distally slender, slightly longer than surstylus (cf. Fig. 17), with basal part short and broad, with distal slender part gradually tapered, straight and somewhat shorter than that of P. (M.) haennii having acute apex and a row of setulae at posterior margin. Ejacapodeme (Fig. 17) robust but relatively simple, basally hardly wider than distally, shorter and less elongate (about 4.5 times as long as its maximum width) than that of P. (M.) haennii.

Figures 23–34. 

Male S6 and structures of genitalia of European Periscelis (Myodris) species. 23–26. P. (M.) haennii sp. nov., paratype: 23. S6; 24. Cercus laterally; 25. Surstylus laterally; 26. Postgonite laterally; 27–30. P. (M.) annulata (Fallén), Slovakia: 27. S6; 28. Cercus laterally; 29. Surstylus laterally; 30. Postgonite laterally; 31–34. P. (M.) piricercus Carles-Tolrá & Verdugo Páez, Switzerland: 31. S6; 32. Cercus laterally; 33. Surstylus laterally; 34. Postgonite laterally. Scales: 0.05 mm (24, 28, 32); 0.1 mm (23, 25–27, 29–31, 33, 34).

Figures 35–36. 

Distal part of male abdomen of two Periscelis (Myodris) species (photographed in situ in ethanol). 35. P. (M.) haennii sp. nov., paratype; 36. P. (M.) annulata (Fallén), Switzerland. Scales: 0.1 mm. Photos by L. Pollini Patrinieri.