Isoperla potanini (KLAPÁLEK, 1923) Zwick & Surenkhorloo, 2005

Zwick, P & Surenkhorloo, P, 2005, The Mongolian Species Of Isoperlinae (Plecoptera: Perlodidae), Acta Zoologica Academiae Scientiarum Hungaricae 51 (3), pp. 253-276 : 266-269

Isoperla potanini (KLAPÁLEK, 1923) , comb. n.

( Fig. 8 )

Mesoperlina potanini KLAPÁLEK, 1923a: 114 , figs 78, 79; RAUŠER 1968: 367, figs 82–98.

Material studied. MONGOLIA: Bajanchongor aimak, Somon Zag, Changaj Gebirge, 2100m, Zag gol, 18.VII.1966, 87 mm, 9 ff [KASZAB 708, 709] ; Chovd aimak, 3 km N Somon Uenč, 1450m, Uenč gol, 2.–4.VII.1966, 3 ff [KASZAB 618] ; Chovd aimak, ca 35 km N Somon Uenč: Mongol Altaj Gebirge, 1750m, kl. Nebenbach des Uenč gol, 8.VII.1966, 2 mm [KASZAB 646] ; Chovd aimak, Somon Altaj, 1350m, Bodončijn gol, 2.VII.1966, 1 m [KASZAB 613] ; Chövsgöl aimak, 8 km N von Somon Burenchaan, 1450m, Delger mörön, 20. VI.1968, 4 mm, 2 ff [KASZAB 989] ; Chövsgöl aimak, 8 km W Somon Burenchaan, 1450m, Delger mörön, 16.VII.1968, 1 f [KASZAB 1117] ; Chövsgöl aimak, Alag Mort, 42 km NO vom Pass Chaldzan Sogotyn davaa, 1900m, Tesijn gol, 14.VII. 1968, 110 mm, 30 ff [KASZAB 1110]; Gobi Altaj aimak, von SO Ecke des Až Bogd ul bis ca 20 km O vom “neuen” Somon Altaj, 1500–1900m ,, 29.VI.1966, 3 ff [KASZAB 600] ; Uvs aimak, Somon Baruunturuu, 1280m, Baruunturuun gol, 25. VI.1968, 2 mm, 1 f, 3 La (putative) [KASZAB 1012] .

Size. Fore wing length, mm 4.7–5.9 mm; ff 6.7–7.7 mm.

Colour pattern. Ochre or light brown, except a brown pattern on head and pronotum ( Fig. 8a ) and the dark brown meso- and metanota. Head with a small rhomboid yellow mark between the ocelli and a yellow mark on frontoclypeus in front of the anterior ocellus. There are large light ochre areas between the compound eyes and the posterior ocelli which extend to the rear of head and are medially separated by a wide brown stripe. Scapus a little darker than rest of antenna. Thorax with a well-defined median pale band; laterally with the usual brownish muscle attachment marks; the lateral edges are light. The cercus segments are distally dark brown, the cerci therefore appear annulate. view, i = egg

The apical brown bands increase in width on distal segments, terminal segments may be completely dark brown.

Structure. Typical of the genus; there are no appendages or flanges on thoracic nota. Legs ( Fig. 8b ) short, femora about 4 times as long as wide, with several setae along ventral edge and also a few dorsally. Tibiae with very sparse apical setae. Cerci with fine ground pilosity and apical crowns of several long setae approximately of equal size ( Figs 8c, d ).

Male. Sternite 8 without ventral lobe ( Fig. 8e ), the intersegmental membrane towards sternite 9 appears a little swollen in side view. Sternite 9 forms a subgenital plate which is almost parallel-sided and apically truncate in ventral view; it covers the elongate paraprocts from below. Paraprocts long, slender, distally little upcurved ( Fig. 8f ). Penis entirely membraneous, no sclerites or large spines. The everted penis resembles the one of I. asiatica in having an unpaired outgrowth on its dorsal side. The membrane is covered with many minute oval and pointed little teeth; near the base are very fine and slender transparent spicules ( Fig. 8g ).

Female. Subgenital plate barely extended backward, slightly and shallowly bilobed, the shallow medial notch angular ( Fig. 8h ). Sternite 9 with a round more strongly sclerotized darker area on each side.

Egg ( Fig. 8i ). About 350 µm long, oval, with 6 blunt longitudinal ribs which reach neither the oval posterior pole nor the flattened anchor pole. Collar simple, stalked, with outwardly bent rim, its base slightly projecting into the egg space. Chorion about 5 µm thick, with distinct coarse irregular punctation. Shape and appearance of eggs varies with degree of hydration. Eggs from dried females appear almost parallel sided and narrow and are about 365 µm long.

Larva (putative). Pale (faded?), the head pattern resembles I. difformis (see ILLIES 1955). Femora and tibiae with fringes of long silky hairs, cerci without any. Dorsal integument with small intercalary setae but without the fine procumbent tomentum-like pilosity that most Isoperla larvae have.

Diagnostic characters and affinities. Originally the present species was included in Mesoperlina and redescribed as such ( RAUŠER 1968). It was ZHILTZOVA (1970) who recognized the characters being typical for Mesoperlina : male tergite 9 raised and with a spinule patch posteriorly on both sides, tergite 10 posteriorly with a pair of erect, horn-like processes, sternite 8 and paraprocts simple. Distinctive female characters of Mesoperlina are not known. ZHILTZOVA recognized that M. potanini does not belong in the genus, but left it unplaced.

Several salient diagnostic features of the present species are not mentioned in the redescription by RAUŠER (1968). We therefore confirmed our identification by examining some of KASZAB’ s material studied by RAUŠER who had compared syntypes in coll. KLAPÁLEK, in the museum in Prague.

I. potanini has some superficial resemblance with I. asiatica through the very narrow transverse sternal lobe on male sternite 8. However, I. potanini differs clearly from all other presently known Mongolian species in that each cercus segment carries a complete apical whirl of several setae, and by the presence of strong erect setae on the ventral edge of the short femur. The short bilobed female subgenital plate, the round spots on sternite 9, and the ribbed egg are also distinctive. However, these differences do not justify the exclusion from genus Isoperla . There are Nearctic species with ribbed eggs ( SZCZYTKO 2005), and pilosity was not described for many species, the distinctness of I. potanini in this respect may only be seeming. The putative larva conforms with other Isoperla species.

I. potanini is presently known from northern and western Mongolia.

Figures

Fig. 8. Isoperla potanini (KLAPÁLEK): a = head and prothorax, b = hind leg, c, d = middle portion of cercus, e = male abdominal tip, ventral view, f = the same, dorsal view; g = cleared penis membrane, details of armatures all at the same magnification but not to scale, h = female abdominal tip, ventral