Isoperla oxylepis subsp. balcanica Rauser 1962

Isoperla oxylepis balcanica Raušer, 1962

(Figs. 1–6, 8–10, 12–16, 18–20, 126)

Isoperla oxylepis balcanica Raušer, 1962 — Raušer 1962: 80 (original description of male); Illies 1966: 414 (catalog); Zwick 1973: 249 (catalog).

Material examined: ALBANIA: Gyalica Ljums (Kukës district, Mts Gjalica e Lumës), 1000–1600 m, 16.07.1918, leg. E. Csiki: 1m (HNHM; I. oxylepis, det. W. Joost 1975); Dibër district: Radomirë, Mts Korab, spring and stream E of the village, N 41°49.032’ E 20°30.016’, 1440 m, 26.06.2007, leg. L. Dányi, Z. Erőss, Z. Fehér, A. Hunyadi, D. Murányi: 4m 13f (HNHM; used for drawings, one male terminalia and eggs prepared for SEM), 2m 2f (CGV); 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: 1f (HNHM; eggs prepared for SEM); Mat district: Gurri i Bardhë, Mts Shkanderbeu, open stream S of the village, N 41°25.839’ E 20°05.518’, 1025 m, 30.06.2007, leg. L. Dányi, D. Murányi: 2m 1f (HNHM).

Diagnosis: This subspecies is characterized by medial penial armature that is nearly circular with its sides being folded but lacking lateral expansions. The scales of the armature are triangular and relatively slender, their length being 3x their width. Lateral penial armatures lacking.

Description: Medium-sized species, macropterous. Body length: males 10.0– 11.5 mm (n=9), females 10.5– 14.0 mm (n=17); forewing length: males 11.0–12.0 mm (n=9), females 11.5–13.5 mm (n=17). General colour yellowish but the meso- and metanotum and the abdomen mostly brown; pilosity of the body and legs short and dense. Head yellow, with a broad U-shaped dark brown patch connecting the three ocelli; tentorial callosities and M-line hardly visible, occiput with brown rugosities laterally (Fig. 1). Eyes as large as the area delimited by the three ocelli. Scape dark brown, pedicel and the following three or four antennomeres are brown, distally darker brown; palpi brown. Pronotum yellow, rectangular, edges angled; rugosities are large and brown, anterior and posterior margins outlined in brown. Mesonotum dark brown but yellow anteriorly and medially, metanotum dark brown. Wings yellowish, veins pale in the anterior fourth of the wings, further veins brown. Ventral surface of thorax mostly pale, meso- and metabasisternum bear two broad, dark brown stripes laterally, medial parts light brown; furcasternites light brown, furcal pits black (Fig. 4). Femora pale but the dorsal surface and the ventral edges brown. Tibiae pale ventrally, brown dorsally; tarsi dark brown.

Male abdomen: First tergite dark brown but yellowish anteriorly and medially. Tergites II–VII entirely dark brown, tergite VIII dark brown or dark brown with yellowish brown marks posteriorly. Tergite IX dark brown or brown, posteriorly it bears an undulating yellowish transverse stripe; tergite X yellowish (Fig. 2). Transverse row of four pigmented spots seen on all but tergite X. Ventral surface of abdomen mostly yellow, sternites II–VIII have a brown transverse anterior line, interrupted in the middle at least on segments VII–VIII; sternites II–VII have a medial transverse row of four, sternite VIII of two spots. Vesicle of sternite VIII brown, as wide as long, its posterior margin slightly truncate; shorter than half of the segment’s length (Fig. 3). Sternite IX yellow but with brown patches anterolaterally, the medial penial armature visible through the integument in the posterior half of the segment. Paraprocts brown, sharp, thin and slightly recurved; cerci dark brown, base of the first cercal segment sometimes paler.

Penis: Divided into four lobes and a basal section in extruded position (Figs. 6, 8–9). The medial penial armature located on the medial lobe adjacent to the ventral lobe, lateral penial armatures lacking. The medial penial armature oval, lateral sides folded; length 150–170 µm, width 130–150 µm (Figs. 10, 12). The scales are triangular and erect, cross section cylindrical (Figs. 10, 12). Their length is 30–45 µm, width 10–15 µm. The ventral lobe is hemispherical, most of the surface covered with small, simple hair-like scales. Lateral sides bald; medial section bears branched hair-like scales and a central patch of strong triangular scales that are resembling to the scales of the medial penial armature but are smaller and not coloured. The medial lobe is long and narrow; sides are smooth but the medial section bears a stripe of branched spike-like scales. This stripe is apically wider and consists of smaller but more numerous scales which are grading into stronger ones towards the tapering end over the medial penial armature (Figs. 13, 15). The lateral lobes are long and slightly bent above the basal section. They bear a lengthwise stripe of small, hydra-like scales (Fig. 14); the stripe rises from the dorsolateral ends of the basal section and continues along the medial lobe. Apical part of the lobe bald, rest of the lobe ventrobasally from the stripe of hydralike scales covered with simple and a few branched hair-like scales. A few sensilla settled in an elongated, diagonal field, both between the hydra-like scales and the hair-like scales. The basal section covered mostly with triangular scales (Fig. 16), but these are grading into hydra-like scales towards the dorsal origin of the lateral lobes, and the section beneath the ventral lobe bears simple hair-like scales. Triangular scales are stronger but sparcer ventrally.

Female abdomen: First tergite dark brown but yellowish anteriorly and medially. Tergites II–IV dark brown, tergites V–VII paler, tergites VIII–IX pale brown, tergite X yellowish with some brown marks. Transverse row of four pigmented spots seen on all segments. Sternites II–VIII yellow with an interrupted transversal anterior line; sternites II–VII have a medial transverse row of four spots, hardly visible on the apical ones. Subgenital plate covers most of sternite VIII and the anterior part of sternite IX, most of the plate yellowish but posterior edge usually somewhat darker; posterior margin rounded (Fig. 5). Sternite IX yellow, bearing two pale brown lateral patches on the posterior half. Sternite X and the paraprocts yellow; cerci dark brown, base of the first cercal segment usually paler.

Egg: Chorion brown, 0.32–0.35 mm long and 0.20–0.25 mm wide (n=30). Shape oval, cross section half moon shaped as one side of all the examined eggs are depressed (Fig. 18), though this shape is possibly an artifact (see Tierno de Figueroa et al. 2000). Hatching line inconspicuous. Micropyles placed in a transverse row on the opercular third, not raised (Fig. 20). Chorion with hardly visible ornamentation of penta- or hexagonal FCIs, but dense, well visible punctation present within each impression. Collar round, rim flanged, bears extended ribs. Anchor flat, anchor surface structure in development stage 1 (unmodified, according to Isobe 1997), and with few globular bodies (Fig. 19).

Larva: unknown.

Affinities: This subspecies differs from I. oxylepis oxylepis in that it has a more nearly circular medial penial armature that consists of relatively longer and narrower scales. Furthermore, the ventral lobe bears strong triangular scales, and the stripe of spike-like scales on the medial lobe is more extended in I. oxylepis balcanica. Both subspecies differ from the closely related I. submontana and I. orobica by the oval medial penial armature, furthermore, the vesicle of sternite VIII is weakly separated in I. submontana. They also can be separated from I. bosnica by the lack of lateral expansions on the medial penial armature.

Ecology and distribution: The subspecies was originally described from the Rila Mountains of Western Bulgaria (Raušer 1962). Later it was reported from Montenegro and Kosovo (Sivec 1980b) and Macedonia (Ikonomov 1986; see also the distribution notes on I. bosnica below) (Fig. 126). In Central Europe and in the northern Balkans it is replaced by the nominal subspecies. Isoperla oxylepis balcanica is newly reported for Albania where it was collected from two streams at the end of June. The locality in the Korab Mountains is above 1400 m, where the stream is flowing across stony substrates and the riparian vegetation is ruderal Mediterranean bush with some willow. The species was quite numerous and found on bushes, sedges and Petasites leaves, in common with Leuctra inermis Kempny, 1899, Amphinemura triangularis (Ris, 1902), Protonemura intricata intricata (Ris, 1902), Nemoura cinerea cinerea (Retzius, 1783), I. albanica and Perla pallida Guérin, 1838. The locality in the Shkanderbeu Mountains is above 1000 m, the stream is flowing across stony substrates in an open grassland, the riparian vegetation consists of ruderal plants and a few small eastern hornbeams. Only a few specimens were found on the hornbeams in common with numerous Perla marginata Panzer, 1799.