Key to Plecoptera nymphs of the Brazilian Amazon

The following key includes eight species whose nymphs have been associated with their adults and 14 morphospecies known only from their nymphs.

1 Two ocelli...........................................................................................2

- Three ocelli ( Enderleina) ............................................................................. 21

2 Body ranging from light yellow to brown. Spot present on head contouring or not the ecdysial suture, reaching the base of ocelli or not, and extending to the area between the ocelli or not. Post-frontal line not curved between ocelli (Figs. 2, 3, 6, 7). Distance between ocelli 0.2 mm. Lacinia with groups of 5 to 7 bristles below the lower tooth. Presence of groups of bristles on the femur. Gills with the following disposition: ASC1, PSC 1 with two trunks, AT2, AT3, PT3, A1 dual trunks; ASC, PSC (2.3) and SL absent ( Anacroneuria)...........................................................................3

- Body ranging from light yellow to dark yellow. Spots absent in the head. Post-frontal line curved between the eyespots (Figs. 5, 8). Distance between the eyespots at least 0.3 mm; Lacinia groups with 6 to 8 bristles below the lower tooth. Absence of bristles on the femur. Gills with the following provision: ASC and PSC [1,2,3] AT [2,3] PT [3] all with simple trunk; and SL with multiple trunks ( Macrogynoplax)....................................................................18

3 Body light yellow.................................................................................... 4

- Body yellow-orange to dark brown........................................................................ 5

4 Body light yellow with little pilosity. Head pale yellow, without spots. Pronotum without spots. Meso- and metanotum without medians spots [AM, PA]....................................................... Anacroneuria minuta (Fig. 13)

- Body brown......................................................................................... 9

5 Head spot exceeding ecdysial suture and ocelli (Fig. 2)....................................................... 6

- Head spot not exceeding ecdysial suture and ocelli (Figs. 3, 6, 7)............................................. 10

6 Body light to dark brown...............................................................................7

- Body yellow-orange to dark yellow...................................................................... 8

7 Body dark brown. M-line inconspicuous. Pronotum with a median area without spots and with posterior median concavity. Meso- and metanotum with medial and lateral spots forming circles or discs, borders pale yellow. [AM, AP, PA, MA, MT, RR]............................................................................ Anacroneuria marlieri (Fig. 14)

- Body light brown. M-line conspicuous. Pronotum with median area pale yellow without median concavity. Meso- and metanotum with inconspicuous spots, lateral borders whitish [AM, PA, MA, AC]........... Anacroneuria manauensis (Fig. 15)

8 Head with M-line inconspicuous. Pronotum with short longitudinal spots, without posterior median concavity. Meso- and metanotum with large median whitish spots [AM]................................. .. Anacroneuria sp. AB1 (Fig. 16)

- Head with M-line conspicuous. Pronotum without median spots, with slight posterior median concavity. Meso- and metanotum with small median yellowish spots [AM]......................................... Anacroneuria sp. AB2 (Fig. 17)

9 Pronotum with long longitudinal median spots, lateral spots small and whitish, with posterior median concavity. Meso- and metanotum with large, medium and small whitish spots spots [PA, MT]................ Anacroneuria singularis (Fig. 18)

- Pronotum without longitudinal and lateral spots with median area lighter, without posterior median concavity. Meso- and metanotum with small spots forming whitish circles [PA]............................ Anacroneuria sp. AB3 (Fig. 19)

10 Head spot not reaching the ecdysial suture, reaching halfway to the frontal area, not reaching the area behind the ocelli [PA, AP]........................................................................ Anacroneuria sp. AB4 (Fig. 20)

- Head spot passing half of the frontal area, reaching the area behind the ocelli (Fig. 2)............................... 11

11 Head spot extending to the area between the ocelli (Figs. 3, 6).................................................12

- Head spot not extending to the area between the ocelli (Fig. 7)................................................17

12 Head spot narrow in the area between the ocelli (Fig. 3)......................................................13

- Head spot wide in the area between the ocelli (Fig. 6)....................................................... 14

13 Body dark yellow to light brown. Head light yellow with the post-frontal area brown. Pronotum without spots, lighter yellow medially. Meso- and metanotum with circular dark yellow or whitish spots [PA]......... .. Anacroneuria sp. AB5 (Fig. 21)

- Body yellow-orange. Head orangish. Pronotum with median and longitudinal yellowish spots. Meso- and metanotum with orange yellow spots medially [AM]............................................. Anacroneuria sp. AB6 (Fig. 22)

14 Head with yellow-orange spot on post-frontal area and between ocelli.......................................... 15

- Head with light brown spot on post-frontal area and between ocelli............................................ 16

15 Pronotum without spots, without posterior median concavity. Meso- and metanotum with a set of bright spots semicircular, not elongated, in the anterior median area [PA, MT].................................... Anacroneuria sp. AB7 (Fig. 23)

- Pronotum with spots circular whitish, with slight posterior median concavity. Meso- and metanotum with spots in the shape of elongated handles that extend from to the upper side to the median area [PA, MT]........ Anacroneuria sp. AB8 (Fig. 24)

16 Body brown. Head with M-line conspicuous, with spot slightly reaching and not passing ocelli, bordering the ecdysial suture. Pronotum with elongated median and longitudinal spots, laterally forming small ellipses and semi-circles, with slight posterior median concavity. Meso- and metanotum with wide anterolateral and posterolateral whitish spots, slightly ovoid, uniform or in the form of semi-circles[PA]................................................... Anacroneuria sp. AB9 (Fig. 25)

- Body light brown. Head with M-line inconspicuous, spot passing ocelli and not bordering ecdysial line. Pronotum with two large spots forming whitish semirectangles, without posterior median concavity. Meso- and metanotum with lateral whitish spots in the form of parentheses “()”, forming elongated “handles” extending from the anterior median area [PA]................................................................................... Anacroneuria sp. AB10 (Fig. 26)

17 Body yellow-orange with ferruginous hue. Head orange with the postfrontal area brown. Pronotum with elongated and uniform median ferruginous spot extending to the lateral, distal and apical borders, contrasting with the surrounding dark brown coloring. Meso- and metanotum with large and uniform median ferruginous spot [PA].... Anacroneuria sp. AB11 (Fig. 27)

- Body light yellow. Head yellow with postfrontal area, dark orange. Pronotum with spots inconspicuous. Meso- and metanotum with uniform yellowish median spot, inconspicuous, of orange color hues [AM]........ .. Anacroneuria sp. AB12 (Fig. 28)

18 Body light to dark yellow with light brown color hues........................................................ 19

- Body dark yellow with greenish and reddish color hues......................................................20

19 Body light yellow. Head light yellow with conspicuous M-line. Pronotum with anterior circular spots and two wide longitudinal median whitish markings of dark brown color hues on the lateral margins. Meso- and metanotum with large whitish median circular spots, with two short and thin dark markings on the lateral margins. [AM]....... Macrogynoplax sp. AB1 (Fig. 29)

- Body dark brown. Head light brown with inconspicuous M-line. Pronotum without markings. Meso- and metanotum with light yellow semicircular median spots, with two dark markings anteriorly slightly wider and posteriorly longer and thinner on the lateral margins [AM, AP, PA]................................................. Macrogynoplax delicata (Fig. 30)

20 Body dark yellow with greenish color hues. Head dark yellow without spots. Pronotum without spots. Meso- and metanotum with large uniform dark yellow medial spot with greenish color hues [AM, AP, PA]...... Macrogynoplax pulchra (Fig. 31)

- Body orange with reddish color hues. Head with elongated triangular spots with reddish color hues lateral to each ocellus, and two inverted U-shaped sinuous markings just below the antero-lateral ecdisyal suture to the compound eyes. Pronotum with dark reddish spots. Meso- and metanotum with light yellow median and lateral markings with reddish borders [AP]................................................................................. Macrogynoplax sp. AB2 (Fig. 32)

21 Body light to dark yellow. Head dark yellow without spots, M-line inconspicuous. Pronotum without spots. Meso- and metanotum without spots [AM, AP, PA]................................................ Enderleina froehlichi (Fig. 33)

- Body pale brow. Head light brown with conspicuous M-line. Pronotum with inconspicuous spots, with two dark marking longer and larger on the lateral margins. Meso- and metanotum with small inconspicuous spots [AM, RR].................................................................................................. Enderleina flinti (Fig. 34)