Isoperla autumnalis, Murányi, 2011

Murányi, Dávid, 2011, Balkanian species of the genus Isoperla Banks, 1906 (Plecoptera: Perlodidae), Zootaxa 3049, pp. 1-46 : 36-40

Isoperla autumnalis sp. n.

( Figs. 109–125, 127)

Type material: Holotype male: MONTENEGRO: Kolašin municipality: Redice, big side stream of the Morača River beneath the village, N 42°50.921’ E 19°20.069’, 560 m a.s.l., 10.10.2008, leg. L. Dányi, D. Murányi ( HNHM: PLP2961 ; used for drawings Figs. 109–112, 114, terminalia prepared for SEM) . Paratypes: same locality and date: 1f ( HNHM: PLP3348 ; used for drawing Fig. 113) , same locality and date: 3 larvae, 1 exuviae ( HNHM: PLP3349 ; used for drawings Figs. 121–123, one maxilla of the exuviae prepared on slide) .

Diagnosis: This species is characterized by a medial penial armature that is divided into an upper and a lower part, where only the upper armature is coloured. Additionally, the upper armature is further subdivided into diverging, elongated left and right parts; the lower medial armature remaining undivided. Scales of the armature are spike-like. Lateral penial armatures small.

Description: Medium-sized species, macropterous. Body length: holotype male 10.5 mm, paratype female 11.0 mm; forewing length: holotype male 11.0 mm, paratype female 12.0 mm. General colour brown but the head and pronotum mostly yellow with dark brown markings; pilosity of the body and legs short and dense. Ground colour of the head yellow, but with large dark brown patch connecting the three ocelli, the tentorial callosities and the M-line, and with a more expanded brown area around the central dark brown patch ( Fig. 109). Tentorial callosities and M-line distinct, a few wrinkles present between the M-line and the lateral margins; occiput lacks rugosities but dark brown laterally. Eyes as large as the area delimited by the three ocelli. Scape dark brown, pedicel and the following ten antennomeres are brown but distal part of the antenna is dark brown; palpi brown. Pronotum yellow, rectangular, edges angled; rugosities are large and dark brown, the surrounding area brown, anterior and posterior lines dark brown under and above the rugosities. Mesonotum dark brown but yellow anteriorly and medially, metanotum dark brown. Wings brownish, especially on the outer posterior half; venation dark brown but the anterior fifth of costa whitish. Ventral surface of thorax mostly pale, meso- and metabasisternum mostly dark brown, furcasternites pale, furcal pits dark brown ( Fig. 112). Femora brown dorsally and pale ventrally, edges dark brown. Tibiae brown ventrally, dark brown dorsally; tarsi dark brown.

Male abdomen: First tergite brown but yellowish anteriorly and medially. Tergites II–VII entirely brown with an interrupted anterior dark brown line. Tergites VIII–IX mostly light brown, but with a medial dark brown mark and an interrupted anterior dark brown line; tergite X yellowish with two brown, triangular patches medially and with posterolateral light brown edges ( Fig. 111). Transverse row of four pigmented spots seen on all but tergite X. Ventral surface of abdomen mostly light brown, sternites II–VIII have a brown transverse anterior line interrupted in the middle, and brown lateral margins; sternites II–VII have a medial transverse row of four spots, sternite VIII with two spots. Vesicle of sternite VIII yellow, as wide as long, its posterior margin is rectilinear and only the edges rounded; nearly as long as half the segment’s length ( Figs. 110, 124). Sternite IX yellowish but with brown patches anteriorly and anterolaterally, the medial penial armature was slightly transparent before extrusion of the penis in the field. Paraprocts brown; cerci dark brown, the first cercal segment brown.

Penis: Divided into four lobes and a basal section in extruded position ( Figs. 114–117, 124). The medial penial armature is divided into an upper and a lower part, only the upper part coloured; upper armature located on the medial lobe on its end at 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. The upper medial penial armature is further divided into a left and a right part which are diverging towards the ventral lobe, elongated and slightly folded. Length of the parts are 260 µm, width 80 µm ( Fig. 118). The lower medial penial armature is undivided, subtriangular. Length 210 µm, width 190 µm ( Fig. 119). The scales are spike-like, those on the lower part are longer and thinner, short ones of the upper armature slightly bent. Their length is 25–60 µm, width 5–10 µm ( Figs. 118–119). Lateral penial armatures are small, consisting of only a few scales arranged in a wide patch. The scales are spikelike, their length is 15–30 µm, width 5–10 µm ( Fig. 120). The ventral lobe is hemispherical, lateral sides bald. Its upper medial section bears small branched hair-like scales, these are grading into bigger ones towards the lower medial penial armature; the lobe bears a medial stripe of triangular scales beneath the armature, small triangular scales occur also basolaterally. The medial lobe is elongated, apical half slightly widening; most of the surface is bald, but bears very small ciliated scales on the ventral third. The lateral lobes are elongated, central part constricted along a transverse stripe of hydra-like scales. This stripe is narrow, rises from the lateral penial armatures and contiues to the upper medial penial armature. Further surface of the lobes is bald besides sparse, small ciliated scales ventrolaterally to the hydra-like scales. Sensilla settled along the lateral part of the lobes, but not in the apical end. The basal section covered mostly with triangular scales, but these are grading 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–VIII entirely brown with an interrupted anterior dark brown line, tergites IX–X paler. Transverse row of four pigmented spots seen on all but tergite X. Sternites II–VIII light brown with a brown transversal anterior line interrupted in the middle, brown lateral margins and a medial transverse row of four spots. Subgenital plate covers most of sternite VIII and the anterior third of sternite IX; anterior part of sternite VIII with two dark patches. Plate light brown with dark brown margins, and an arrow-like dark brown patch medially; posterior margin rounded with a weak tip ( Fig. 113). Sternite IX light brown, bearing two large dark brown lateral patches. Sternite X and the paraprocts light brown; cerci dark brown.

Mature larva: Body length of: 10.5 mm (n=1). General colour dark brown but with yellowish markings and pale legs ( Fig. 121). Pilosity usual for the genus, pronotal, posterior tergal and cercal fringes relatively long and acute; swimming hairs present on the femora, tibiae and metatarsi, distal half of the cerci with scarce dorsal hair fringe of erect hairs five times longer than distal whorl of setae. Head dark brown with a yellow spot in front of anterior ocellus, interocellar spot small, a figure 8-shaped yellow 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. 122). 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, inner lacinial margin with seven stout setae and a row of short tin setae below subapical tooth; galea with long setae on the whole surface ( Fig. 123). Pronotum rounded, dark brown with a wide yellow stripe medially, lateral fields with pair of small yellow elongate spots, lateral margins yellow. Mesonotum and metanotum mostly dark brown with pale, marbled pattern medially; wingpads whitish, with a large central dark brown stripe. Meso- and metasternum pale, furcasternites and furcal pits slightly darker. Legs pale, dorsal surface of femora and tibiae slightly darker. Abdominal tergites dark brown with a pair of elongated yellow spots medially. The spots decreasing in size towards the last tergite which is entirely dark brown; tergites VI–IX bear narrow lateral yellow markings. Transverse row of paired pigmented spots seen on all but the last segment. Ventral surface of abdomen pale brown, the distal segments darker. Paraprocts brown; cerci light brown in the basal segments, distal part yellowish.

Egg: unknown.

Affinities: See I. tripartita tripartita above.

Ecology and distribution: The species was collected at a big stream at 560 m in the upper Morača valley in October ( Fig. 125, 127). Besides the imagos, one mature and two earlier instar larvae were collected, indicating a true autumnal flight period. The stream has rapid flow with cascades, and stony substrate, with sandy patches at slow or marginal sections. The stream flows through a rocky, forested gorge; the riparian vegetation consisting of Rubus , Petasites and some tall plants. The species was found in common with Leuctra mortoni feheri Murányi, 2007 , L. major , L. hirsuta , L. jahorinensis Kaćanski, 1972 , Protonemura hrabei Raušer, 1956 , P. nitida ( Pictet, 1836) , Perla pallida and Besdolus illyricus Kovács & Zwick, 2008 . The new species is apparently rare since all the accompanying species were also collected from several similar habitats in the area.

Etymology: The name autumnalis (from the Latin world autumnalis, means autumnal) refers to the autumnal flight period of the species. Used as an attributive adjective, gender neutral.