Isoperla citrina, Murányi, 2011

Murányi, Dávid, 2011, Balkanian species of the genus Isoperla Banks, 1906 (Plecoptera: Perlodidae), Zootaxa 3049, pp. 1-46 : 12-16

Isoperla citrina sp. n.

( Figs. 26–42, 127)

Type material: Holotype male: ALBANIA: Dibër district: Radomirë, Mts Korab , torrent E of the village, N 41°49.131’ E20°30.160’, 1460 m a.s.l., 26.06.2007, leg. D. Murányi ( HNHM: PLP2589 ; used for drawings Figs. 26–29) . Paratypes: same locality and date: 1m ( HNHM: PLP3038 ; used for drawing Fig. 30, terminalia prepared for SEM), 1m ( CGV, penial armatures prepared on slide) .

Diagnosis: This small-eyed, pale species is characterized by a medial penial armature that is oval with two lateral and one medial longitudinal ridge. The scales of the medial armature are drop-shaped in dorsal view, triangular in lateral view, while the scales of the lateral armatures are spike-like.

Description: Medium-sized species, macropterous. Body length: holotype 10.0 mm, paratypes 10.0– 10.5 mm (n=2); forewing length: holotype 11.0 mm, paratypes 10.5–11.0 mm (n=2). General colour bright yellow (especially in life), with few dark brown markings; pilosity of the body and legs short and dense. Head yellow with a dark brown V-shaped line connecting the ocelli; tentorial callosities and M-line barely visible, occiput lacking rugosities ( Fig. 26). Eyes smaller than the area delimited by the three ocelli. Scape dark brown, pedicel basally yellowish, the following three or four antennomeres are yellowish but the remainder is dark brown; palpi dark brown. Pronotum yellow, rectangular, edges angled; rugosities are large but few and not prominent, light brown coloured. Meso- and metanotum yellow with some dark patches on the posterior half. Wings yellowish, venation pale in the anterior half, costa and the distal few millimetres of the longitudinal veins brown; posterior half of the wing membrane indistinct brownish markings. Ventral surface of thorax yellow, meso- and metabasisternum bear two elongated brown patches in the line with the base of coxae; furcasternites light brown, furcal pits black ( Fig. 29). Femora yellow with longitudinal dark brown stripe on the dorsal and on ventral edges. Tibiae yellowish, tarsi brown.

Male abdomen: First five tergites dark brown; the next three are yellow but having a dark brown longitudinal medial and an anterior transverse line. Tergite IX has only a transversal anterior line interrupted in the middle, tergite X yellow with very pale posterior triangular patches ( Fig. 27). Transverse row of four pigmented spots seen on all but tergite X. Ventral surface of abdomen yellow, sternites II–VIII have a brown transverse anterior line interrupted in the middle; sternites II–V have a medial transverse row of four spots, while sternites VI–VIII have two. Vesicle of sternite VIII brown, as wide as long, its posterior margin is nearly truncate with only the edges rounded; as long as one third of the segment’s length ( Fig. 28). Sternite IX uniformly yellow, the medial penial armature can be seen through its posterior half. Paraprocts brown, blunt, thin and slightly recurved; the first two cercal segments yellow but distal part of the cerci are dark brown.

Penis: Divided into four lobes and a basal section in extruded position ( Figs. 30–33). The medial penial armature located on the medial lobe on its end at the ventral lobe. Lateral penial armatures located on the basal section just beneath the lateral lobes. The medial penial armature is oval with two lateral and one medial longitudinal ridge; length 230–240 µm, width 190–200 µm ( Fig. 34). The scales are drop-shaped in dorsal view ( Fig. 35), triangular in lateral view; some of them, especially in the medial groove, are shark-teeth shaped ( Fig. 36). Their length is 10–25 µm, width 5–10 µm, height in lateral view about 25 µm. Lateral penial armatures are triangular, length 160–170 µm, width 90 µm ( Fig. 37). The scales are spike-like, their length is 15–60 µm, width less than 10 µm; the apical ones are much longer than the basal ones. The ventral lobe is hemispherical, covered with small, mostly simple hair-like scales only in a median stripe ( Fig. 40). The medial lobe is long and narrow, smooth besides the medial penial armature. The lateral lobes are long and curved above the lateral penial armatures. They bear a transverse stripe of small, hydra-like scales ( Fig. 38); the stripe rises dorsally to the lateral penial armatures and broadens toward the medial lobe. A few sensilla are settled in an elongate field on the sides, both between the hydra-like scales and on the bald surface. The basal section bears triangular scales in addition to the lateral penial armatures, which are settled in a stripe spread between the lateral penial armatures, beneath the ventral lobe ( Fig. 39); scales are thinner and sparse midways.

Female, egg, larva: unknown.

Affinities: Isoperla citrina is a member of the rivulorum group. The three ridges of the medial penial armature distinguishes it from all the other members of this group. A similar structure is known in I. goertzi , but it has only two ridges, the shape of the armature is different and the scales are longer and narrower. Among the Isoperla species with similarly pale habitus, the new species is similar to I. flava also with small compound eyes, but the shape of the penial armatures and their scales are quite different.

Ecology and distribution: The species was collected at the end of June from a high gradient stream above 1400 m in the Korab Mountains ( Figs. 40–41, 127). This stream flows through a small limestone gorge with extensive riffles over coarse substrates. Slower sections flow over gravel and sand substrates. Riparian vegetation varies from tall sedge to Mediterranean bush and low willows. The species was found on sedges and on Petasites leaves in common with Leuctra inermis , Amphinemura quadrangularis Zwick, 1978 , Protonemura intricata intricata , I. albanica and Perla pallida . This species is apparently rare since I. albanica was more numerous than it and the accompanying species were found also at additional localities in the area.

Etymology: The name citrina (from the Latin word citrus, means lemon tree) refers to the bright yellow colour of the living insect, and is considered an adjective, gender feminine.