Isoperla tripartita tripartita Illies, 1954

Murányi, Dávid, 2011, Balkanian species of the genus Isoperla Banks, 1906 (Plecoptera: Perlodidae), Zootaxa 3049, pp. 1-46 : 23-32

Isoperla tripartita tripartita Illies, 1954

( Figs. 67–98)

Isoperla tripartita Illies, 1954 — Illies 1954: 118 (original description of male and female); Illies 1955: 99 (repr. of Illies 1954); Gulička 1955: 628 (supplementary description of male); Winkler 1956: 337 (supplementary description of male); Winkler 1957: 62 (supplementary description of male); Illies 1966: 422 (catalog); Berthélemy 1971: 46 (description of larva); Zwick 1973: 252 (catalog); Kis 1974: 237 (supplementary description of male and female); Raušer 1980: 102 (supplementary description of larva); Tierno de Figueroa et al. 2001: 69 (description of egg).

Isoperla tripartita tripartita Illies, 1954 — Raušer 1963: 807 (supplementary description of male); Zwick 1978: 230 (supplementary description of male).

Isoperla graeca Aubert, 1956 — Aubert 1956: 206 (original description of male and female); Aubert 1964: 295 (supplementary description of male, refers to Isoperla illyrica Tabacaru, 1971 ); Illies 1966: 404 (catalog); Zwick 1978: 230 (syn. fide).

Isoperla tripartita graeca Aubert, 1956 — Raušer 1963: 805 (stat. n., supplementary description of male).

Material examined: AUSTRIA: Niederösterreich: Wienerwald, Eckbach , 13.05.1999, leg., det. W. Graf: 1m 1f ( HNHM; used for drawings Figs. 67–71) ; HUNGARY: Veszprém county: Eplény, Mts Bakony, Malomvölgyi Stream , 05.05.1972, leg. S. Újhelyi: 1m 2f ( HNHM; I. grammatica , det. S. Újhelyi) ; Bakonybél, Mts Bakony, Tisztavíz , 24.06.1972, leg., det. S. Újhelyi: 1m 4f ( HNHM) ; Baranya county: Mánfa, Mts Mecsek , 14.06.1957, leg. L. Móczár, det. W. Joost 1974: 5m 8f ( HNHM; eggs prepared for SEM) ; Komló, Mts Mecsek, Takanyó valley , 21.05.1991, leg. L. Ábrahám: 2m 2f ( HNHM; one penial armature prepared on slide) ; Magyaregregy, Mts Mecsek, Vár-völgyi Stream , 300 m, 26.06.2006, leg. J. Kontschán, D. Murányi: 1m 1f ( HNHM) ; Tolna county: Váralja, Mts Mecsek, Váraljai Stream , 26.05.2005, leg. Gy. Sziráki: 1m ( HNHM) ; Bátaapáti, Mts Mecsek, Hutai Stream , 13.05.2006, leg. Z. Fehér, L. Tamás: 1m ( HNHM) ; Komárom-Esztergom county: Dömös, Mts Visegrádi, Szőkeforrás valley , 16.06.1988, leg. L. Tóth: 1m 2f ( HNHM) ; Pest county: Visegrád, Mts Visegrádi, Apátkuti valley , 19.05.1965, leg.?: 3m ( HNHM) ; 10.05.1986, leg. L. Tóth: 1m ( HNHM; I. belai , det. L. Tóth) ; 21.06.1992, leg. L. Tóth: 2m ( HNHM) ; Szentendre, Mts Pilis, Bükkös Stream , 20.05.1974, leg. S. Újhelyi: 1f ( HNHM) ; 25.05.1977, leg. S. Újhelyi: 1m ( HNHM) ; 30.05.1977, leg. S. Újhelyi: 8m 2f ( HNHM) ; Szokolya, Mts Börzsöny, Hártókút , 14.04.1966, leg. H. Steinmann: 1m 1f ( HNHM; I. belai , det. H. Steinmann) ; Les-völgyi Stream , 11.06.1987, leg. L. Tóth: 2m 5f ( HNHM) ; Királyrét, Nagyvasfazék Stream , 20.05.1992, leg. L. Tóth: 4m 5f ( HNHM) ; Kemence, Mts Börzsöny, Királyháza , Kemence Stream , 380 m, 14.06.2005, leg. M. Földvári, D. Murányi, L. Papp: 1m 2f ( HNHM; used for drawing Fig. 72, male terminalia prepared for SEM) ; Nógrád county: Diósjenő, Mts Börzsöny, Kemence Stream , 25.07.1986, leg. L. Tóth: 1f ( HNHM) ; 12.06.1991, leg. L. Tóth: 1m 1f ( HNHM) ; Kemence Stream , 430 m, 03.05.2006, leg. M. Földvári, D. Murányi, L. Papp: 1 larva ( HNHM) ; Málna Stream , 450 m, 03.05.2006, leg. M. Földvári, D. Murányi, L. Papp: 2 larvae ( HNHM; used for drawings Figs. 91–93, one maxilla prepared on slide) ; Szécsény, Mts Cserhát, Pösténypuszta , Ipoly River , 21.05.2005, leg. K. Balogh, K. Harmos, D. Murányi: 1m ( HNHM; penial armature prepared on slide) ; Pásztó, Mts Mátra, Hasznos Stream , 27.07.1967, leg. H. Steinmann: 1m 3f ( HNHM) ; ROMANIA: Mureş county: Brâncoveneşti , 12.05.1971, leg., det. B. Kis: 6m 6f ( HNHM; one penial armature prepared on slide) ; Caraş- Severin county : Băile Herculane, 07.1907, leg. Schmidt, det. W. Joost 1975: 3m ( HNHM; one penial armature prepared on slide) ; Mehedinţi county: Staricea ( Vaskapu ), 20.05.1969, leg., det. B. Kis: 3m 1f ( HNHM; pigmy population, one penial armature prepared on slide) ; BOSNIA-HERZEGOVINA: Foča region: Dobro Polje, Toplica spring and Dobropoljka Stream at the bridge, N 43°35.658’ E 18°29.697’, 995 m, 03.06.2009, leg. W. Graf: 3m 4f ( CWG) ; Sutjeska National Park, Jabušnica sastavski, N 43°17.413’ E 18°37.040’, 765 m, 02.06.2009, leg. W. Graf: 1m ( CWG) ; Sutjeska National Park, Cestu Spring beside the road, N 43°15.902’ E 18°35.567’, 1110 m, 02.06.2009, leg. W. Graf: 3m 2f 1 larva ( CWG) ; MONTENEGRO: Pljevlja municipality: Pljevlja, Breznica Stream , 01.05.2008, leg. V. Pešić: 1m ( HNHM; penial armature prepared on slide) ; Kozička Stream at its influence to Ćeotina River , 26.06.2008, leg. V. Pešić: 1m ( HNHM; penial armature prepared on slide) ; Berane municipality: Berane, Monastiri George Spring , N 42°51’9.2” E 19°51’41.3”, 30.05.2009, leg. W. Graf: 6m 6f ( CWG) ; Monastiri Chocho , N 42°51’9.2” E 19°51’41.3”, 30.05.2009, leg. W. Graf: 7m 15f ( CWG) ; Kolašin municipality: Biogradska Gora National Park, Biogradska Stream , affluence of Biogradsko Lake , N 42°53’33.0” E 19°36’09.7”, 1115 m, 02.06.2009, leg. W. Graf: 3m, 1 larva ( CWG) ; Andrijevica municipality: Gnjili potok, N 42°45’02.0” E 19°41’51.0”, 1125 m, 30.05.2009, leg. W. Graf: 1m ( CWG) ; Visitor Mts, Murino, Murinska River , small streams and spring, N 42°39’17.6” E 19°52’47.6”, 880 m, 30.05.2009, leg. W. Graf: 4m, 1 larva ( CWG) ; Plav municipality: Gushinje, Alipašini Springs , N 42°33’0.5” E 19°49’33.1”, 930 m, 31.05.2009, leg. W. Graf: 18m 6f ( CWG) ; 09.06.2009, leg. W. Graf: 1m ( CWG) ; Brezojevica, Lim River at Plavsko Lake , N 42°36’28.9” E 19°55’39.0”, 920 m, 30.05.2009, leg. W. Graf: 1m 1f ( CWG) ; KOSOVO: Pejë municipality : Peć ( Ipek ), 02.07.1917, leg. E. Csiki, det. W. Joost 1975: 1m ( HNHM) ; MACEDONIA: Čaška municipality: Nežilovo, Mts Jakupica, Babuna Spring , 08.07.2008, leg. T. Deli, B. Pál-Gergely, P. Subai: 2m 12f ( HNHM; used for drawing Fig. 95, one penial armature prepared on slide, one male terminalia and eggs prepared for SEM) ; ALBANIA: Shkodër district: Okol, Mts Prokletije, karst spring N of the village, towards Pejë Pass , N 42°25.664’ E 19°45.704’, 990 m, 30.05.2005, leg. K. Balogh, Z. Barina, D. Murányi, D. Pifkó: 4m ( HNHM; used for drawing Fig. 96, two penial armatures prepared on slides) ; karst spring system N of the village, N 42°25.347’ E 19°45.680’, 885 m, 01.06.2005, leg. K. Balogh, Z. Barina, D. Murányi, D. Pifkó: 1m ( HNHM) ; stream along the path towards Pejë Pass , N 42°24.496’ E 19°45.271’, 1010 m, 30.05.2005, leg. K. Balogh, Z. Barina, D. Murányi, D. Pifkó: 1m 2f ( HNHM; used for drawing Fig. 94, penial armature prepared on slide, eggs prepared for SEM) ; Theth, Mts Prokletije, Shalë River , N 42°23.695’ E 19°46.265’, 750 m, 03.06.2005, leg. K. Balogh, Z. Barina, D. Murányi, D. Pifkó: 1f, 1 larva ( HNHM) ; Tropojë district: Dragobi, Mts Prokletije , Valbonë valley above the village, N 42.460700° E 19.905750°, 890 m, 04.06.2009, leg. Z. Barina, G. Lunk, D. Schmidt: 1m ( HNHM; penial armature prepared on slide) ; Tropojë, Mts Prokletije, open stream on Mt. Callumit , N 42.498620° E 20.124430°, 1970 m, 07.06.2009, leg. Z. Barina, G. Lunk, D. Pifkó, D. Schmidt: 1m ( HNHM) ; Has district: Kruma ( Krumë ), 06.06.1918, leg. Alb. Exp.: 2m ( WNHM; I. graeca , det. J. Aubert 1963; penial armatures prepared on slides Nr. 9–10) ; Kukës district: open brook along the Novoselë–Kolesjan road, N 41°56.594’ E 20°29.879’, 1800 m, 24.06.2007, leg. L. Dányi, Z. Erőss, Z. Fehér, A. Hunyadi, D. Murányi: 18m 12f ( HNHM; one penial armature prepared on slide, eggs prepared for SEM) ; Bicaj, Mts Gjalica e Lumës , Shkallë Bicaj , Tershanë Stream , N 41°59.518’ E 20°25.333’, 500 m, 25.06.2003, leg. Z. Erőss, Z. Fehér, J. Kontschán, D. Murányi: 3m 5f ( HNHM; used for drawing Fig. 97, one penial armature prepared on slide, eggs prepared for SEM) ; Ploshtan , 22.07.1918, leg. Alb. Exp.: 1m ( WNHM; I. graeca , det. J. Aubert 1963; penial armature prepared on slide Nr. 7) ; Dibër district: Radomirë, Mts Korab, Radomirë Stream E of the village, N 41°49.022’ E 20°30.022’, 1445 m, 28.06.2007, leg. L. Dányi, Z. Fehér, D. Murányi: 3m 2f ( HNHM; one penial armature prepared on slide) ; spring and torrent beneath Fushë Korabit , N 41°49.207’ E 20°30.727’, 1770 m, 28.06.2007, leg. L. Dányi, Z. Fehér, D. Murányi: 1m 1f ( HNHM) ; open brook beneath Fushë Korabit , N 41°49.149’ E 20°31.304’, 1875 m, 28.06.2007, leg. L. Dányi, Z. Fehér, D. Murányi: 1m 1f ( HNHM) ; Fushë Korabit , spring and wet meadow, N 41°49.210’ E 20°31.563’, 1880 m, 26.06.2007, leg. L. Dányi, Z. Erőss, Z. Fehér, A. Hunyadi, D. Murányi: 1f ( HNHM) ; open brook above Fushë Korabit , N 41°49.121’ E 20°32.240’, 1905 m, 27.06.2007, leg. L. Dányi, Z. Erőss, Z. Fehér, A. Hunyadi, D. Murányi: 6m 8f, 2 larvae ( HNHM; one penial armature prepared on slide, one male terminalia and eggs prepared for SEM) ; spring and open brook above Fushë Korabit , N 41°49.251’ E 20°31.543’, 1940 m, 28.06.2007, leg. L. Dányi, Z. Fehér, D. Murányi: 1m 1f, 1 larva ( HNHM) ; Mts Dejë, Varoshit Stream at Shkanderbeu Cliff , N of Murrë Pass, N 41°38.792’ E 20°11.390’, 975 m, 26.06.2003, leg. Z. Erőss, Z. Fehér, J. Kontschán, D. Murányi: 1m 3f ( HNHM) ; Librazhd district: Qarishtë, Mts Jablanica , brook E of the village, N 41.24569° E 20.51238°, 1900 m, 04.07.2008, leg. Z. Barina, D. Pifkó, A. Vojtkó: 1m 2f ( HNHM; one penial armature prepared on slide) ; Steblevë, Mts Jablanica, Zall i Barik Stream S of the village, N 41.28893° E 20.47496°, 1730 m, 03.07.2008, leg. Z. Barina, D. Pifkó, A. Vojtkó: 2f ( HNHM; eggs prepared for SEM) ; brook SE of the village, N 41.27905° E 20.50103°, 1865 m, 03.07.2008, leg. Z. Barina, D. Pifkó, A. Vojtkó: 3m 5f ( HNHM; two penial armatures prepared on slides) ; Skrapar district: Çeramica, Mts Ostrovicë , stream W of the village, N 40°32.780’ E 20°27.527’, 1535 m, 06.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 3m 2f ( HNHM; one penial armature prepared on slide) ; brook W of the village, N 40°32.649’ E 20°26.573’, 1820 m, 05.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 7m 1f ( HNHM) ; Backë, Mts Ostrovicë, spring section of Mrbret River beneath Faqekuq Peak, N 40°31.752’ E 20°21.153’, 1970 m, 05.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 1f ( HNHM) ; stream beneath the pass between Frengu and Faqekuq peaks, N 40°31.614’ E 20°25.021’, 1915 m, 04.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 6m 11f ( HNHM; used for drawing Fig. 98, two penial armatures prepared on slide, eggs prepared for SEM) ; E slope of Frengu Peak, N 40°31.561’ E 20°24.917’, 1900 m, 04.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 1m ( HNHM) ; Mts Ostrovicë, brook beneath the Ostrovicë Peak, N 40°34.051’ E 20°26.846’, 1960 m, 06.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 6m 5f ( HNHM) ; spring between Ostrovicë and Faqekuq peaks, N 40°33.485’ E 20°25.074’, 1715 m, 07.07.2005, leg. Z. Barina, D. Pifkó, D. Schmidt: 6m 1f ( HNHM) ; GREECE: Florina prefecture: Pisoderi, Mts Verno , forest stream 3km W of the village, N 40°47’16.5” E 21°13’26.7”, 1315 m, 15.05.2006, leg. L. Dányi, J. Kontschán, D. Murányi: 1m, 1 exuviae ( HNHM; male terminalia prepared for SEM) ; Ioannina prefecture: Milea , 5km SW of the village, 1300 m, 09.06.1992, leg. M. Gerecke, det. G. Vinçon: 3m 3f ( HNHM; one penial armature prepared on slide, eggs prepared for SEM) .

Diagnosis: The medial penial armature of this species is divided into upper and lower coloured portions. The upper medial armature is further divided or subdivided into diverging, elongate left and right parts, lower medial armature subdivided; scales spike-like. Its lateral penial armatures are small to vestigial.

Description: Large-sized species, but a pigmy population was also found (Staricea, Romania, see also Remarks); macropterous. Body length: males 12.5–14.5 mm (n=30), females 13.0–16.0 mm (n=30); forewing length: males 12.5–15.0 mm (n=30), females 13.5–16.5 mm (n=30). Pigmy males are 9.0–10.0 mm (n=3), female 10.0 mm; forewing lenght: males 9.5–10.5 mm (n=3), female 10.5 mm. General colour yellowish but the meso- and metanotum and the abdomen mostly brown; pilosity of the body and legs short and dense. Head rounded, yellow with an X-shaped dark brown patch connecting the three ocelli and the apical parts of the M-line ( Fig. 67); on Balkanian specimens it is sometimes modified to a upturned U ( Fig. 98), or can be rather extensive ( Figs. 94–97). Tentorial callosities and M-line more or less distinct, occiput brown laterally and usually lacks rugosities ( Figs. 67, 96), but the rugosities sometimes can be rather numerous ( Fig. 95). Eyes as large as the area delimited by the three ocelli ( Figs. 67, 94-97), or slightly smaller ( Fig. 98). Scape dark brown, pedicel and the following three or four antennomeres are brown but distal part of the antenna is dark brown; palpi brown. Pronotum yellow to brown, rectangular, edges angled; rugosities are small and usually not so numerous, brown coloured, anterior and posterior lines brown under and above the rugosities. Mesonotum dark brown but yellow anteriorly and medially, metanotum dark brown. Wings yellowish, venation pale in the anterior third, costa and the other veins brown. Ventral surface of thorax mostly pale, meso- and metabasisternum bear two dark brown stripes laterally, furcasternites pale, furcal pits black ( Fig. 70); some extremely dark coloured Balkanian populations have entirely dark meso- and basisternum with dark furcasternites. Femora pale but the dorsal surface and the ventral edges brown. Tibiae pale ventrally, brown dorsally; tarsi brown.

Male abdomen: First tergite dark brown but yellowish anteriorly and medially. Tergites II–VI entirely dark brown, tergite VII entirely dark brown or dark brown with pale marks posteriorly. Pale markings become more extensive on tergites VIII–IX, but a medial dark brown mark always present; tergite X yellowish with two brownish, triangular patches medially ( Fig. 69). Transverse row of four pigmented spots seen on tergites I–VIII, tergite IX usually have two spots, tergite X lacks spots. Ventral surface of abdomen mostly yellow, sternites II–VIII have a brown transversal anterior line, usually interrupted in the middle; sternites II–VII have a medial transverse row of four spots, sternite VIII with two spots. Vesicle of sternite VIII brown, as wide as long, its posterior margin is weakly rounded; as long as half the segment’s length ( Fig. 68). Sternite IX yellow but with brown patches anterolaterally and sometimes with a dark medial area, the medial penial armature visible in the posterior half. Paraprocts brown, sharp, thin and recurved; cerci dark brown, base of the first cercal segment usually paler.

Penis: Divided into four lobes and a basal section in extruded position ( Figs. 72–75). The medial penial armature is divided into an upper and a lower part, both are coloured, though the lower part sometimes rather pale; upper armature located on the medial lobe adjacent to the ventral lobe, lower armature located on the central part of the ventral lobe. Lateral penial armatures located on the lateral lobes just above the basal section, but sometimes vestigial and uncoloured. The upper medial penial armature is further divided or subdivided into left and right arms which are diverging towards the ventral lobe, elongated and usually stripe-like but never drop-shaped, sometimes slightly folded. Length of the parts are 300–450 µm, width 120–200 µm ( Figs. 76–78). The lower medial penial armature is subdivided into left and right arms which are diverging towards the basal section, usually forming an upturned V. Length 250–370 µm, width 100–250 µm ( Figs. 76–78). The scales are spike-like, those on the lower part are usually longer and thinner, short ones of the upper armature sometimes bent. Their length is 40–110 µm, width 5–10 µm ( Figs. 79–80). Lateral penial armatures are usually small, consisting of only a few scales arranged in an elongated patch. The scales are spike-like, their length is 15–40 µm, width 5–10 µm ( Fig. 81). The ventral lobe is hemispherical, lateral sides bald. Its upper medial section bears small branched hair-like scales ( Fig. 82), these are grading into bigger ones towards the lower medial penial armature; the lobe bears a medial stripe of strong triangular scales beneath the armature ( Fig. 83), triangular scales also occur basolaterally. The medial lobe is elongate, apical half slightly widening; most of the surface is bald, but bears very small ciliated scales above the upper medial penial armature ( Fig. 84). The lateral lobes are elongated, central part constricted along a transverse stripe of hydra-like scales. This stripe is narrow arises from the lateral penial armatures and continues to the upper medial penial armature. Other surfaces of the lobes are bald to sparsely covered with small ciliated scales ventrolaterally grading into to the hydra-like scales. Sensilla are settled along the lateral part of the lobes, but not apically. The basal section is covered with mostly triangular scales, but these grade into hydra-like scales towards the dorsal origin of the lateral lobes.

Female abdomen: First tergite dark brown but yellowish anteriorly and medially. Tergites II–VI entirely dark brown, pale markings become more extensive on tergites VII–IX, but a medial dark brown mark always present; tergite X yellow or with some brownish patches medially. Transverse row of four pigmented spots seen on all but tergites IX-X. Sternites II–VII yellow with an interrupted transverse anterior line, and a medial transverse row of four spots. Subgenital plate covers most of sternite VIII and the anterior part of sternite IX; anterior part of sternite VIII with two dark patches. Plate usually uniformly yellow; posterior margin rounded, tip sometimes slightly notched ( Fig. 71). Sternite IX yellow, bearing two pale brown lateral patches on the posterior half. Sternite X and the paraprocts yellowish; cerci dark brown, base of the first cercal segment usually paler.

Egg: Chorion dark brown, 0.31–0.35 mm long and 0.22–0.26 mm wide (n=30). Shape oval, opercular end usually depressed ( Figs. 85–88). Hatching line inconspicuous. Micropyles placed in a transverse row on the opercular third, not raised, each take place close to the meeting of carinae between the FCIs ( Fig. 90). Chorion with marked ornamentation of penta- or hexagonal FCIs, sometimes with undulated edges. Collar round, rim flanged or slightly flanged, sometimes with depressed ditch at the base; bears one or two rows of FCIs ( Fig. 89). Anchor flat, anchor surface structure in development stage 1 (unmodified), according to Isobe (1997), globular bodies distributed in the whole area ( Fig. 89).

Mature larva: Body length of the matured larva: 14.5–17.5 mm (n=10). General colour brown but with yellowish markings and pale legs ( Fig. 91). Pilosity usual for the genus, pronotal, posterior tergal and cercal fringes relatively short and blunt; swimming hairs present on the femora, tibiae and metatarsi, distal half of the cerci with scarce and inconspicuous dorsal hair fringe of erect hairs as long as distal whorl of setae. Head brown or dark brown with a yellow spot anterior to the M-line, interocellar spot large, closed off posteriorly by pigment, a large spot between the posterior ocellus and the compound eye on each side, and a pair of spots posterior to the complete occipital row of setae ( Fig. 92). M-line distinct, tentorial callosities barely visible; eyes normal sized. Scape, pedicel and the following five or six antennomeres are light brown, distal part of the antenna yellowish; palpi yellowish, mouthparts light brown. Lacinia bidentate, triangular, with 7–9 strong setae situated on a shallow mound beneath subapical tooth, thin hairs present all along the inner margin to near base; galea with long setae on the inner, and short setae on the outer margin ( Fig. 93). Pronotum rounded, dark brown but with a wide medial yellow stripe along the medial suture, a pair of elongate dark brown areas and light inclusions present, lateral margins yellow. Mesonotum and metanotum mostly dark brown but with pale, marbled pattern; wingpads whitish, with an elongated central brown stripe. Ventral surface of thorax pale, furcasternites and furcal pits slightly darker. Legs pale, dorsal surface of femora and tibiae slightly darker. Abdominal tergites brown to dark brown with two more or less continuous, light coloured, longitudinal stripes along the abdomen. Tergites also bear lateral yellow markings, but these are sometimes lacking on the first and last one or two tergites. Transverse row of pigmented spots present, but sometimes hardly seen on all but the last segment. Ventral surface of abdomen pale brown, the distal segments usually darker. Paraprocts brown; cerci light brown in the basal segments, distal part yellowish.

Affinities: It differs from I. tripartita recta by having divergent left and right arms of the upper medial penial armature instead of parallel arms. Both subspecies differ from the closely related I. obliqua and I. pesici by their elongate, but never tear drop-shaped (as in I. obliqua ) or rounded ( I. pesici ), appearance of the upper medial penial armature. The West Balkanian I. illyrica differs by having an undivided upper medial penial armature that consists of short scales; and I. autumnalis differs by having an uncoloured and undivided lower medial penial armature. Furthermore, I. autumnalis , I. illyrica and I. pesici lack the dark brown lateral stripes on the ventral surface of the thorax that are characteristic for most of the I. tripartita tripartita specimens, and the head pattern is rather different from the typical pattern of I. tripartita tripartita . In addition, I. autumnalis is the only autumnal Isoperla species known from the Balkans. The notched subgenital plate that does not continue as a short sulcus was regarded (e.g. Kis 1974) as a distinguishing feature of I. belai (formerly assigned to the tripartita group). A slightly notched subgenital plate also occurs in I. tripartita tripartita . The larva can be distinguished from that of I. autumnalis by the more extended pale markings, especially on the wingpads and the stripes on the abdomen.

Ecology and distribution: The species was originally described from the Wienerwald of Austria ( Illies 1954). Later it was reported from Slovakia, the Czech Republic, Hungary, and Romania in Central Europe, and all of the Balkan countries ( Fochetti 2004, Sivec 1980a, 1980b). In the Alps I. tripartita tripartita is known only from the Eastern foothills ( Graf 1999). It was collected in the western and the southern Carpathians but there are only a few data from the northern and the eastern Carpathians ( Fiałkowski & Kittel 2002, Kis 1974, Krno 2003, Zhiltzova 1977). In the Carpathian Basin it is the most frequent Isoperla of streams and brooks of the submontane and hilly regions, but it is missing from the Transsylvanian Mountains where it is seems to be replaced by I. belai ( Kis 1974) . It is widely distributed in the Balkans, where inhabits not only the hilly and submontane waters but is also found in mountain streams, being a typical inhabitant of high montane open brooks. The specimens were collected from April to July, but mostly in the second half of May and the first half of June in the Carpathian Basin. In the Balkanian high montane populations, adults were present in June and July. The accompanying fauna consists of widely distributed European species common to the Carpathian Basin (e.g. Brachyptera risi ( Morton, 1896) , Capnia bifrons ( Newman, 1839) , Leuctra hippopus Kempny, 1899 , Protonemura intricata intricata , Nemoura cinerea cinerea ). It was collected with a much richer stonefly fauna within the Balkans.

Remarks: Isoperla tripartita tripartita shows rather high variability that suggests that further splitting of the taxon may be warranted. Unfortunatelly, SEM studies of the penis did not provide additional characters useful to this purpose, since the variability in the specimens involved both the coloured penial armatures and the body colour pattern, but not the distribution of the uncoloured penial armatures. Investigation using molecular methods, drumming signals, and closer examination of morphological features will be required to tease out meaningful differences in this variable taxon.

Isoperla graeca was distinguished from I. tripartita by the presence of lateral penial armatures ( Aubert 1956); however, Zwick (1978) showed that the types of I. tripartita also possess small lateral armatures and synonymized the two species. Raušer (1963) reported that specimens from the Bulgarian Stara Planina and Strandcha Mountains have no lateral penial armatures, at character state in agreement with the original description. Zwick (1978) himself reported such specimens from the Greek Euboea Island. Some of the specimens studied herein seemingly lack the armatures, but at least a few uncoloured spike-like scales have been observed in these specimens when slide mounted. Vestigial and well developed lateral armatures sometimes occur in the same population, suggesting that this character state is of minor taxonomical value.

The morphology of the medial penial armatures is highly variable, including the shape and length of the arms of the upper medial armature, the degree of folding of the medial armatures, and the degree of subdivision, shape and length of the lower medial armature (see Figs. 76–78, Raušer 1963: Figs. 4–5, 7A and Zwick 1978: Figs. 72b– e). These different forms occur in the same population; hence, they not correspond to geographical areas. Conversely, most of the body colour pattern variations are geographically delimited and more or less constant in a given population. Hungarian populations agree well with the specimens from Wienerwald ( Figs. 67–71); this typical colour pattern occurring sporatically in the Balkans, at low altitudes or in high mountains (e.g. foothills of the Verno Mountains, Greece or the higher parts of the Korab Mountains, Albania). Specimens from the Romanian Carpathians have a conspicious head pattern with dense rugosities on the occiput ( Kis 1974: Fig. 146A); single specimens from Kosovo and the Kozička Stream, Montenegro have the same colouration. A similar, but pigmy, population was found at Staricea, Mehedinţi county of Romania. Some specimens from Montenegro and most of the North Albanians have a head pattern as illustrated on Fig. 97. Other Montenegrian and Bosnian specimens have a head pattern reminiscent of I. albanica ( Fig. 43). Specimens from the Ostrovicë Mountains of Albania, and from Berane, Montenegro have the palest head pattern showed on Fig. 98, but typical populations were also found in the Ostrovicë Mountains. Specimens from Babuna Spring, Macedonia ( Fig. 95), some specimens from the Prokletije Mountains, Albania ( Fig. 94) and some specimens from Montenegro (Biogradska Gora, and some specimens from the Visitor Mountains) are strikingly dark coloured. Here, the ventral surface of the thorax lacks the dark brown lateral stripes that are characteristic for all the other forms, and reminds to those of I. bosnica ( Fig. 24). Some specimens from the Jablanica Mountains, Albania have a similarly dark head pattern, but these occur in common with forms from the lower parts of the Korab and Prokletije Mountains ( Fig. 96), and also with more typical specimens. The colour pattern of the studied larvae seem to be less variable than those of the imagos, but the larvae of the particularly dark forms are notably darker than the typical specimens.

It is worth mentioning that all the studied eggs distinctly differ from the I. tripartita eggs described from the Peloponnes, Greece (Tierno de Figueroa et al. 2001), as they have polygonal ornamentation on the chorion instead of punctation on the Greek eggs. This type of ornamentation reminds to those described below for I. pesici , but the Greek eggs differ with having a long collar. Given to its locality of origin, the description of Tierno de Figueroa et al. (2001) possibly refers to the unknown egg of I. obliqua .