an overlooked European species of Periscelididae (Diptera), with notes on the morphology and terminology of terminalia

. Periscelis ( Periscelis ) fugax sp. nov. is described and illustrated based on series of specimens from Portugal and the Czech Republic. It is probably widespread in Europe but has not been previously recognized from the closely related and externally very similar P. ( P. ) winnertzii Egger, 1862. The new species differs from P. winnertzii not only in structures of the male and female terminalia (illustrated) but also in colour pattern of pedicel and mesonotum. Morphology of the male and female terminalia is studied in detail in both these species and terminology of their structures is discussed and rede ﬁ ned. A new modern key to Palaearctic species of Periscelis (s. str.) species is constructed.


Introduction
The world taxa of Periscelididae (including Stenomicridae as subfamily Stenomicrinae) have recently been catalogued by MATHIS & RUNG (2011), including a taxonomic conspectus of this group and a key to extant subfamilies, genera and subgenera. Based on this catalogue, the Periscelidinae = Periscelididae (s. str.) comprises 6 genera and 27 extant species; the genus Periscelis Loew, 1858 is represented by 15 extant species placed in subgenera as follows: Myodris Lioy, 1864 (Holarctic: 5 species), Notioscelis Mathis, 1993 (Australian: 1 species) and Periscelis s. str (Holarctic, Oriental, Neotropical: 9 species). Simultaneously, PAPP & WITHERS (2011) revised the Palaearctic Periscelidinae (= Periscelididae s. str., i.e. glycerine under a binocular microscope. After examination, all parts were transferred to a small plastic tube in glycerine and pinned below the respective specimens. Detailed examinations were performed with a compound microscope (Jenaval) and genital structures were drawn by means of Abbe's drawing apparatus on this microscope at a higher magnifi cation (130-350×). For more details see ROHÁČEK (2006). A detailed description of the new species is provided because all previous redescriptions of P. winnertii (including the most recent in PAPP & WITHERS 2011) are incomplete, lacking many important characters shared with the new species.
The general formation of the male genitalia of Periscelididae (s. str.) [i. e. without Stenomicridae] is very distinctive due to the peculiar modifi cation of the phallapodeme which is extended to form a large pocket-shaped (hood-like in PAPP & WITHERS 2011) capsule that is ventrally fused with the hypandrial frame. This is a strong synapomorphy of the family occurring obviously in all genera including Periscelis where the phallapodeme is much larger than the epandrium (see Fig. 6).
The epandrium is relatively small, arch-shaped (Figs 6, 11, 12, ep) but provided with a pair of distinctive but slender anteroventral appendages or projections, fi rmly connected (not movable) with the epandrium. This (fi rst) pair of appendages is considered to represent true surstyli (Figs 6,12,ss) in agreement with PAPP & WITHERS (2011) but this structure is not homologous with the "surstylus" of authors (e.g. SINCLAIR 2000, CUMMING & WOOD 2009) because their "surstylus" is in fact homologous with the gonostylus (as interpreted here). In the subgenus Periscelis (s. str.) the true gonostyli are relatively small (Figs 6,11,12,gs) and represent a second pair of genital appendages. PAPP & WITHERS (2011) call this paired structure incorrectly "epandrial process". They are recognizable as gonostyli because they are movably connected with the medandrium (= intraepandrial sclerite, = fused remnants of gonocoxites), thus surely not derived from the epandrium (cf. Fig. 12). While the medandrium (Figs 11,12,ma) is reduced but still distinct in Periscelis (s. str.) species, it seems to be entirely absent in the subgenus Myodris where also the gonostyli disappeared (cf. also PAPP & WITHERS 2011: Figs 22, 33). Such extensive reduction to absence of (true) gonostyli is very unusual in Acalyptrates as also is the presence of true (though unmovable) surstyli in Periscelis spp. Note: the surstylus in Periscelididae, particularly its less projecting form in species of the genus Scutops Coquillett, 1904(see PAPP & WITHERS 2011 seems to be homologous with the "anteroventral process of epandrium" variously developed in species of the fossil Eocene genus Protanthomyza Hennig, 1965 (Anthomyzidae), see ROHÁČEK (2013a: Figs 1F, 2E, 6B). The third pair of genital appendages is formed by postgonites. They belong to the internal genitalia and are situated more medially being attached to the basal part of aedeagus (Figs 6,14,pg). The last (fourth) pair of genital appendages are the cerci (Figs 6,11,ce). They are enlarged, slender, elongate, setose and positioned most caudally. In species of Myodris the male cerci are armed by strong spines on apex (cf. PAPP & WITHERS 2011: Figs 21, 27, 35, 39) and may have a clasping function to substitute the (here missing) gonostyli.
The internal genitalia are formed by hypandrial and aedeagal complexes. In Periscelis species the hypandrial complex is represented only by the hypandrium (Fig. 6, hy). It is low, frame-shaped but posteriorly medially attenuated to submembranous. Dorsally it is fused with the ventral margins of the pocket-shaped part of phallapodeme and can be best recognized laterobasally where it is more sclerotized (Fig. 6). In Myodris and Scutops species, the hypandrium is more distinctly separated from phallapodeme (cf. PAPP & WITHERS 2011: Figs 22, 33, 52). The posterior sclerotized parts of the hypandrium (see Fig. 12, hy, rest of hypandrium removed in this illustration) are attached to the basal parts of the gonostyli, if these are present. Pregonites (= appendages of hypandrium) are not developed.
The aedeagal complex is formed by the phallapodeme, ejacapodeme, aedeagus (phallus) and postgonites. The phallapodeme (Fig. 6) is extremely enlarged, bulging dorsally to form a cup-like structure fused ventrally with the hypandrial frame and serving as a protection to the distiphallus. In addition to this large cup-like part, the phallapodeme has in Periscelis (s. str.) also a smaller basal part (Fig. 6, bpha) being formed as a short, ventromedially deeply forked, sclerite which is closely attached to and/or partly fused with the anterior pocket-shaped part. In Myodris species both these parts of the phallapodeme are fused completely. Ventral arms of the basal part of the phallapodeme reach to base of aedeagus (see Fig. 14, bpha). Also the ejacapodeme (Fig. 6, ea) is large, rod-like but basally somewhat widened to forked, situated in the ejaculatory duct (Figs 6, 12, ed) above the phallapodeme and serving as a part of the sperm-pump. The aedeagus is undivided, with phallophore reduced and not separated from the distiphallus (Figs 6, 14 dp), which is very elongate, ribbon-like, curved to twisted, weakly sclerotized and pale-pigmented, partly hidden in the phallapodemal pocket. A pair of postgonites is attached to basal part of aedeagus (Figs 6,14,pg).
Internally there are two distinct structures of female genitalia belonging to the 8th segment. Spermathecae (2+1) are characterized by heavily sclerotized and dark spherical bodies (Figs 18,32), robust and long ducts reinforced either by an internal spiral structure or other sclerotization (cf. PAPP & WITHERS 2011: Fig. 20) and by the very short fused part of ducts in the paired spermathecae (Figs 18,32). Female genital chamber is largely membranous, but anteriorly projecting in a digitiform submembranous ventral receptacle having a small tail-like projection on apex (Figs 19,31).
Cephalic chaetotaxy: all setae blackish brown; pvt well developed (although shortest of frontal setae), divergent, situated between posterior ocelli at dorsal margin of occiput; vti robust, longest of cephalic setae, upright, very slightly inclinate; vte, oc and ors subequal in length, strong but distinctly shorter than vti; vte lateroclinate; oc strongly proclinate and very slightly divergent, arising ouside ocellar triangle; only 1 reclinate ors situated in middle of orbit; 1-3 microsetulae in front of ors; no vibrissa or pseudovibrissa but with 2-3 short ventro-reclinate setae on ventral side of vibrissal angle and anterior part of gena; 3-5 inclinate setae also on lateroventral margin of face; gena posteriorly to vibrissal part with a series of 5-6 thicker and longer ventroclinate peristomal setae, becoming shorter posteriorly; no genal seta; expanded part of postgena and occiput behind eye with numerous short setae being stronger near posteroventral eye margin; posteroventral angle of occiput with a cluster of setae, 2 longer than others; postocular setulae behind posterodorsal margin of eye numerous, dorsally in single, ventrally in 2-3 rows.
Thoracic chaetotaxy (Fig. 3): all setae and setulae blackish brown; ac setulae numerous, in 8 rows on suture, with 4 rows reaching almost to scutellum, none of them enlarged; 2 strong postsutural dc, the anterior half length to two-thirds of the more robust posterior, 8-11 dc setulae in front of anterior dc but no setulae between dc setae; 1 strong hu (postpronotal) seta plus 4-5 setulae on humeral callus; 2 strong npl, anterior as long as hu, posterior shorter; 1 sa (as long as hu) and 1 shorter pa; 2 sc, apical as long as posterior dc, laterobasal shorter than anterior dc; 1-3 (usually 2) fi ne setulae between apical sc but they can often be broken off; 1 short but distinct ppl; anepisternum with a group of short setulae in posterodorsal corner; 2 stpl (katepisternal) setae, anterior always shorter, numerous setulae on disc and 3-4 longer but fi ne setae on ventral corner of katepisternum.
Wing (Fig. 2) relatively broad, with pale brown membrane darker fumosely spotted in some parts and ochreous to dark brown veins. Wing pattern is characterized by infuscation of distal part of cell r 2+3 , around apex of R 4+5 , area around r-m, M between r-m and dm-cu, around basal part of CuA 1 and of entire alula. Veins are darkened in all these parts and also distal half of R 1 and A 1 are dark brown. C not interrupted, uniformly setulose, reaching to apex of R 4+5 . Sc short, ending free in subcostal cell but its curvature to C indicated by venal fold. R 2+3 long, very slightly bent to sinuate, ending closer to apex of R 4+5 than M. R 4+5 straight to indistinctly sinuate and terminating in wing apex. Distal part of M apically slightly recurved, diverging from R 4+5 . Cross-vein r-m situated in distal half of dm cell; cross-vein dm-cu present but attenuated or even interrupted by spurious vein. CuA 1 distally slightly bent, ending near wing margin. Cells bm and cup developed, veins in the latter are attenuated. A 1 distinct but not reaching wing margin. Alula relatively large, dark, with marginal ciliation as long as that of anal lobe of wing. Wing measurements: length 2.78-3.61 (holotype 3.61) mm, width 1.03-1.29 (holotype 1.24) mm, Cs 3 : Cs 4 = 0.44-0.58, rm/dm-cu : dm-cu = 1.48-1.88. Haltere with yellowish stem and relatively large, dirty white, knob.
Legs (Figs 1, 4) yellow or yellowish white and brown variegated on fore coxa (with ventral part pale yellow) and all femora, tibiae and tarsi; setosity brown. Extent of dark areas seems to be variable, particularly on femora. Generally f 1 and f 2 have two (often incomplete) brown rings, a paler ring basally and a darker ring subapically (with knees yellow) while f 3 is brown along most of its length dorsally with complete ring subapically leaving knee and ventral basal portion yellow. All tibiae have two brown rings, a proximal below knee and a distal subapically but t 1 has distal ring longer, almost reaching apex of tibia. Tarsi are yet lighter, yellowish white to (fore tarsus) white, each with 2 distal segments brown. Chaetotaxy: f 1 with a series of 6-8 long and thicker posteroventral setae and with a double row of shorter and fi ner upright posterodorsal setae; f 2 posteroventrally with a row of numerous fi ne setae (longest about three-fourth of maximum width of femur); t 1 with 1 slightly longer posterodorsal seta; t 2 with 1 distinct and thicker ventroapical seta (about as long as maximum width of tibia); remaining parts of legs uniformly setulose, without peculiarities.
Postabdomen: T6 relatively large, although narrower and somewhat shorter than T5, transverse but tapered posteriorly, setose similarly and also bearing lateral silvery spots as have T3-T5 (Fig. 4). S6 (= pregenital sternum, Fig. 13) narrower and paler than S5, suboblong, with sparse setae at posterior margin and with distinct posteromedial narrow depression. In front of epandrium there is a virtually symmetrical arch-shaped synsclerite formed probably by fusion of T7, S7 and S8. This synsclerite is shortly setose only in posterior half and has embedded 7th spiracles in its lateral parts.
Postabdomen 20,21) broad anteriorly, strongly tapered posteriorly. T6 large, fl at, with lateral part somewhat bent ventrally, brown, with well developed lateral white and silvery microtomentose spots (Fig. 15), fi nely setose in posterior half and laterally (setae longest). S6 simple (Fig. 20), transversely suboblong, smaller (particularly shorter) than S5, ochreous with lateral darkening and sometimes with a pair of diffuse darker spots on disc, with 2 pairs of longer setae at posterior margin besides short setosity. 6th spiracle in membrane very close to margin of T6 (Fig. 20). T7 and S7 fused to form ring-shaped tergosternum T7+S7 (Figs 15, 20, 21) which is brown except for pale ventromedial part; ventrally with more setae than dorsally, with longest setae at posterior margin laterodorsally. 7th spiracle situated laterally, in T7+S7 (Fig. 21). T8 forming a bent, relatively narrow brown sclerite (Fig. 16), fi nely but relatively long setose in posterior two-thirds. S8 (Fig. 17) separate, about as wide as T8 but slightly shorter, densely setose on entire disc, yellow with characteristic brown darkening along lateral and posterior margins. Genital chamber membranous, elongate, without sclerotized structures; ventral receptacle ( Fig. 19) submembranous, digitiform but distally dilated, having regularly fi nely striated slender proximal part and somewhat tuberculate distal widening, the latter with a tail-like, apically attenuated and twisted projection. Spermathecae (1+2) globular (Fig. 18), blackish brown and heavily sclerotized; a pair borne on common duct often larger than single one; spermathecal ducts long and relatively broad, internally strengthened by spiral structure; the terminal fork connecting 2 spermathecal bodies very short. T10 (supraanal plate) absent (Fig. 21). S10 (subanal plate) reduced (Figs 20, 21), short, crescent-shaped, weakly sclerotized and pale-pigmented, covered by micropubescence and with 2-3 minute setulae posterolaterally. Cercus (Figs 20, 21) relatively small, short, subovoid, with rich fi ne setae and fi ne micropubescence; apical seta longest, as long as cercus. Etymology. The new species is named fugax because one of the meanings of this Latin adjective is "passed unnoticed" to refl ect the fact that species has been so long overlooked. Relationships. Periscelis fugax sp. nov. has formerly been mixed with the very similar P. winnertzii Egger, 1862 which undoubtedly is its nearest known relative. According to PAPP & WITHERS (2011) P. winnertzii has no close ally among Palaearctic species of Periscelis (which they interpret as a genus in a narrower concept, i. e. without other subgenera). Despite the fact that there is now an additional species, P. fugax sp. nov., having similar venation and structures of the male and female genitalia, we agree with them, that this species-pair does not deserve to be classifi ed in their own supraspecifi c taxon as did ENDERLEIN (1936) for P. winnertzii establishing for it a separate genus Parclioscena Enderlein, 1936.
Figs 11-14. Periscelis (P.) fugax sp. nov., male paratype (Portugal: Valongo). 11 -external genitalia caudally (surstyli omitted); 12 -same, cranially (cerci omitted); 13 -pregenital sternum (S6), ventrally; 14 -aedeagal complex, laterally (only basal part of distiphallus depicted). Scale = 0.1 mm. For abbreviations see p. 231. cercus with relatively short setae on apex. In the female terminalia no synapomorphy can be revealed because these structures remain undescribed in other species of the subgenus. Biology. The species seems to be associated with sap runs of oaks because the majority of type specimens were collected in this habitat (cf. also ROHÁČEK et al. 2016, as P. sp. cf. winnertzii), thus living similarly to P. winnertzii (see below). Interestingly, P. fugax has hitherto not been  (Figs 16-19). For abbreviations see p. 231. found to co-occur syntopically with P. winnertzii although both species can apparently be sympatric (confi rmed for Portugal). Almost all specimens examined were found in September-October, only singletons in June, July and August.
Distribution. Periscelis fugax is probably widespread in Europe: it has hitherto been recorded from Portugal and Czech Republic (both Bohemia and Moravia) but is surely also living in intervening areas. It has previously been recorded from the Czech Republic (Podyjí NP) by MÁCA et al. (2005) under the name P. winnertzi, see the type material. Two of the specimens recorded by ROHÁČEK et al. (2016) as P. sp. cf. winnertzii from Portugal were subsequently found not to belong to P. fugax but to true P. winnertzii (see material examined under that species).
Further differences against P. fugax sp. nov.: Male head with gena lighter, brownish only at ventral margin. Antenna with apex of 1st fl agellomere more rounded, with little prominent anterodorsal corner (Fig. 5). Arista with 5 long dorsal and 3-4 long ventral rays. Cephalic chaetotaxy with some setae (vte, oc) slightly longer and thicker, also peristomal setae distinctly more robust. Thorax darker than in P. fugax not only as regards microtomentose pattern on mesonutum and darker scutellum but also pleural part of thorax darker, with longitudinal pale band narrower. On mesonotum ac setulae more numerous, in up to 10 rows on suture; macrosetae more robust, particularly anterior dc longer. Wing with fumose spots defi nitely smaller, less distinct: that in the middle restricted to close surrounding of r-m and those in wing apex (at ends of R 2+3 and R 4+5 ) small, often poorly visible. Knob of haltere partly yellow on tip. Legs not different from those of P. fugax. Male preabdomen with the same blackish brown bands on T3-T5 but S3-S5 distinctly darker, entirely uniformly brown. Postabdomen of similar construction but S6 markedly dissimilar in shape and pigmentation (see diagnosis). Male genitalia different not only in form of surstylus, gonostylus and postgonite (see above) but also cercus (Fig. 27) differently setose (densely proximally, sparsely distally) and ejacapodeme (Fig. 23) of different shape, particularly proximally.
Female with sexually different coloration of face as in P. fugax but with gena lighter, all yellowish white, not brownish at vibrissal angle. Abdomen with T3-T5 dorsomedially paler brown than laterally. Sterna S3-S5 uniformly ochreous (thus lighter than in male), see S5 in Fig. 28. Postabdomen broader anteriorly, with S6 distinctly longer and less transverse than that of P. fugax and 6th spiracle in margin of T6 which is more bent ventrally (Fig.  28). Differences in pigmentation and setosity of T8 (Fig. 29) and S8 (Fig. 30) are stressed in the above diagnosis. Ventral receptacle (Fig. 31) digitiform but not widened distally, with similarly fi nely striated proximal part but distal part also striated, not tuberculate and terminal small projection different, distally thicker. Spermathecae (Fig. 32) very similar to those of P. fugax but larger compared to ducts. Setae on cercus shorter, the apical in particular (Fig. 28).

Remarks:
Periscelis winnertzii had formerly been classifi ed in several genera and/or subgenera and its name has been variously misspelled (see review of synonymies above). In EGGER'S (1862) original description it is named "winertzii" but this is an evident typographical or typing error because the species was named according to Johann Winnertz whose name is written correctly in the derivatio nominis in EGGER'S (1862) paper, see also PAPP & WITHERS (2011: 356). Consequently, SCHINER (1863: 272) emended the species' name correctly. P. winnertzii and its sister species P. fugax surely do not belong to a separate supraspecifi c taxon inasmuch as their genitalia are of the same construction as those of the type species of Periscelis, viz. P. annulipes Loew, 1858. Classifi cation of P. winnertzii within subgenus or genus Myodris (and its synonyms, see above) was also incorrect because based on the (plesiomorphic) presence of posterior cross-vein (dm-cu). In reality, dm-cu is distinctly attenuated or interrupted by a spurious vein in both these species, indicating a fi rst step to reduction of the cross-vein being so characteristic of other Periscelis (s. str.) species. Biology. The biology of P. winnertzii was studied by PAPP (1998) in Hungary. Adults emerge in mid July to beginning of September. They lay eggs in September. The larvae live in sap runs in black oozing wounds on old oak trees, and during autumn develop to third instar which is the overwintering stage. Mature (third instar) larvae were found as late as in May. Pupariation occurs on wet bark in June or July. Adults occur from June to September (most commonly in September) but the two specimens examined from Portugal were found already towards the end of June. Distribution. Also P. winnertzii is probably widely distributed in Europe. Because formerly mixed with P. fugax, the reliable records are only those revised by PAPP & WITHERS (2011) from Poland (Breslau = Wrocław), Austria and Hungary and those recorded here from Portugal (new) and Slovakia. A record by ROHÁČEK (2013b) from the latter country also is correct (revised). Previous records of P. winnertzii from other countries, summarized by MATHIS & RUNG (2011), viz. from Great Britain, France, The Netherlands, Switzerland and Germany are to be checked as they can partly deal with P. fugax. The same can be true for the fi nding of the species in Spain (CARLES-TOLRÁ & PAGOLA-CARTE 2013). On the other hand the species is to be (for the time being) deleted from the fauna of the Czech Republic (MÁCA 2009) because all specimens recorded by MÁCA et al. (2005) proved to belong to P. fugax.

Discussion
The examination of the male genitalia of P. fugax sp. nov. and some of its relatives (including two species of the subgenus Myodris) raised some doubts about the generic classifi cation of Palaearctic Periscelididae sensu stricto as proposed by PAPP & WITHERS (2011). The absence of gonostylus (= epandrial process of authors), used by PAPP & WITHERS (2011) to argue for the separation of Myodris Lioy, 1864 as a genus different from the rest of Periscelis is not restricted to this group. Apart from Myodris species the gonostylus disappeared also in the New World genus Scutops Coquillett, 1904 (as found by PAPP & WITHERS 2011: 366-369) and even in the Afrotropical Periscelis stuckenbergi Mathis & Freidberg, 2012 from Ethiopia having been originally classifi ed in the subgenus Periscelis s. str. (MATHIS & FREIDBERG 2012). Moreover, the structures of the male genitalia (and female terminalia in particular) are unknown in some other (Neotropical) genera placed in Periscelididae (s. str.). It should also be stressed that the loss of gonostylus has not necessarily occurred only once and, consequently, this character need not be synapomorphic for all the taxa discussed above. In our opinion it seems premature to change the generic classifi cation of Periscelididae (s. str.) until it can be based on serious phylogenetic analysis including also characters of terminalia in all known taxa. For this reason we have followed the nomenclature and the generic and subgeneric classifi cation used by MATHIS & RUNG (2011).