Isoperla altaica Sámal 1939

Teslenko, Valentina A. & Zhiltzova, Lidiya A., 2006, Nymphs of the genus Isoperla Banks (Plecoptera, Perlodidae) from the Eastern Palaearctic Region, Zootaxa 1130, pp. 1-33 : 2-5

Isoperla altaica Sámal 1939

( Figs. 1–7)

Description. Zapekina­Dulkeit (1955) originally described the nymph of I. altaica and her work agrees well with our understanding of the species. However, due to the freshness of our material, we can provide additional information about the color patterns of the nymph. Length of mature male nymph (excluding cerci) 7.0– 9.5 mm, female 8.0–12.0 mm; cerci of male 4.0–4.5; cerci of female 5.0– 5.5 mm. General body color pale­brown with contrasting pale and brown pattern on dorsum of head ( Fig. 1), pale, median longitudinal stripe on dorsum of thorax and abdomen; ventrum brownish, tip of abdomen slightly darker. Clothing hairs present on body surface.

Head with transverse occipital spinule row complete, two pale spots posterolateral to compound eyes extending from occiput to anterior ocelli ( Fig. 1); small, oval, pale spot in front of anterior ocellus with lateral arms extending to base of antennae; labrum with median pale spot. Lacinia ( Fig. 2 ) bidentate, triangular, gradually narrowed to tip; inner lacinial margin with row of five or six long stout setae below subapical tooth, and a few short, thick setae interspersed; base of lacinia with many finer hairs. Galea slightly prolonged, its tip exceeds the base of subapical tooth ( Fig.2 ). Mandible ( Fig. 3 ) with six unserrated teeth and two rows of setae: first setal row extends from the base of the first tooth, the second from the base of the fourth.

Thorax. Pronotum ( Fig. 1) transverse­oval, fringed with short stout setae, occasional long hairs interspersed at upper and lower angles; medial field pale, slightly narrowed to darkened anterior and posterior margins; lateral margins pale; sublateral fields brownish, each enclosing small pale spot. Meso­ and metanota with pale stripe medially, dark sublaterally, with two pair of pale spots within; margins pale. Legs ( Fig.4 ) pale, covered by thick, pale clothing hairs; femora and tibiae fringed with silky swimming hairs along dorsal margin; short, dark setae along ventral tibia margin.

Abdominal terga ( Fig. 1) brownish, with pale stripe medially; and narrow, pale stripes laterally. Cerci pale, without fringe of swimming hairs ( Figs. 5–7 ); 6–7 apical segments long, and with a whorl of short seta and 1 long seta ventrally.

Material examined: Russia. Altai Mnts., Telesckoye Lake, Vtoraya Rechka, 4.V 1989, Eu. Makarchenko, 1 nymph; Telesckoye Lake, Uodor R., 23.V 1989, Eu. Makarchenko, 1 nymph; Tuekta R., upstream, Seminsky Pass, 23.V 1989, Eu. Makarchenko, 1 nymph.

Distribution. Russia: Altai Mnts., Sayan Mnts., Transbaikal Region, South of the Magadan Region; Mongolia.

Figures

FIGURES 2 – 7. Isoperla altaica: 2. Right maxilla, ventral. 3. Right mandible, ventral. 4. Right leg, dorsal. 5 – 7. Basal, medial, and apical sections of right cerci, lateral. Scale (mm): 4 = 0.6; 2, 3, 5 – 7 = 0.4.