Isoperla

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 : 30-31

Key to nymphs of the East Palaearctic Isoperla species

1. Head with irregular and medially more or less widely interrupted occipital spinule row. Cerci, in apical half with dorsal, or both dorsal and ventral, silky hair fringes ( Figs. 27–28; 13–14). Setal whorls of terminal cercal segments with one dorsal and (or) one ventral setae longer than others ( Figs. 28, 48, 41, 60) .................................... 3

­ Head with complete occipital spinule row. Cerci, without silky hair fringe ( Fig. 7, 21). Setal whorls of terminal cercal segments with one ventral seta longer than others ( Figs. 7, 21) ................................................................................................................... 2

2. Abdomen with single, wide pale stripe surrounded by brown pigment ( Fig. 1)............. ................................................................................................................ I. altaica Sámal

­ Abdomen with alternating light and dark bands ( Fig. 15) ... I. eximia Zapekina­Dulkeit

3. Apical half of cerci with fringe of long silky hairs on dorsal side only ( Fig. 41). Lacinia triangular ( Fig. 36) ........................................................................................... 4

­ Apical half of cerci with fringes of long silky hairs on both dorsal and ventral sides ( Figs. 13–14). Lacinia ( Fig. 9) subquadrate ........................................ I. asiatica Raušer

4. Apical cercal whorl of terminal segments with one vental setae longer than others (sometimes only twice the others) ( Figs. 40–41; 59–60).............................................. 5

­ Apical cercal whorl of terminal segments with one dorsal and one ventral setae longer than others ( Figs. 47–48)............................................................................................... 8

5. Galea tip reaches base of subapical lacinial tooth ( Fig. 55).......................................... 6

­ Galea tip does not reach a base of subapical lacinial tooth ( Fig. 36)............................ 7

6. Head ( Fig. 54) pale, U­shaped spot of frontoclypeus open anteriorly; occiput mostly pale. Pronotum ( Fig. 54) with medial, pale, cross­shaped spot. Abdominal terga ( Fig. 54) with medial pale stripe composed of a row heart­shaped spots................................ ....................................................................................................... I. obscura Zetterstedt

­ Head ( Fig. 49) with pale spot of frontoclypeus closed anteriorly, or nearly so, by a thin transverse dark stripe; occiput mostly dark. Pronotum ( Fig. 49) without cross­shaped stripe, pattern more complicated. Abdominal terga ( Fig. 49) with paired rounded pale spots surrounding a brown median stripe ................................... I. mongolica Zhiltzova

7. Frontoclypeus with U­shaped, dark spot curved anterior to anterior ocellus ( Fig. 35), lateral margins of this spot do not reach antennal bases; occiput with curved transverse darken band between compound eyes narrowed medially ( Figs. 35) ............................. ......................................................................................................... I. lunigera Klapálek

­ Head with brown M­band connecting antennal bases and limited to anterior of epicra­

nial suture ( Figs. 29); occiput completely pale ................................... kozlovi Zhiltzova 8. Dark M­band limited anteriorly by a well defined pale M­line, large pigmented areas in anterior of frontoclypeus ( Figs. 22; 61) .................................................................... 9

­ Dark M­band limited anteriorly by a well defined pale M­band, large unpigmented areas in anterior of frontoclypeus ( Figs. 42, 68) ......................................................... 10

9. Frontoclypeus ( Fig. 22) darker than general body color, with dark­brown M­band and distinct, pale M­line. Lacinia ( Fig. 23) with small rounded subapical projection. Tip of galea reaches the base of subapical tooth ( Fig. 23) .... I. flavescens Zhiltzova & Potikha

­ Frontoclypeus ( Fig. 61) brownish, pigment more diffuse and does not contrast with general body color, M­line pale, indistinct. Lacinia ( Fig. 62) triangular, without subapical projection. Galea small its tip does not reach the base of subapical tooth ( Fig. 62). ........................................................................................................... I. ornata Zhiltzova

10. Pronotum ( Fig. 42) with pale cross­shaped spot. Frontoclypeus without spots. Abdomen ( Fig. 42) with distinct, dark, median stripe and alternating rows of contrasting dark and pale stripes. Cerci without clothing hairs ( Fig. 46–48) .................................... ....................................................................................................... I. maculata Zhiltzova

­ Pale pronotum ( Fig. 68) spot not cross­shaped; anterior of frontoclypeus with two pale spots ( Fig. 68). Medial stripe of abdomen ( Fig. 68) consisting of a wide, pale, mesal longitudinal row of rounded spots, with a faintly darker median line. Cerci ( Figs. 72– 74) covered with thin clothing hairs ........................................ I. pseudornata Zhiltzova