Systenus

Key to males of Systenus from Costa Rica

1 All femora yellow.................................................................................... 2

- At least one femur with some brown cuticle................................................................. 4

2 Cercus short, wide and subrectangular (Figs 4 d, e); tibiae yellow with brownish vestiture; postpedicel basally subrectangular and yellow, and abruptly narrowed to elongate dark brown tapering point distally (Fig. 4 c)............. S. parkeri sp. nov.

- Cercus elongate and digitiform (Figs 1 d, f); tibia I white with ivory colored vestiture; postpedicel various.............. 3

3 Wing apex brown, and posterior membrane reduced near apex so vein M forms the posterior margin (Fig. 1 e); CuAx ratio> 1.0................................................................................. S. maculipennis sp. nov.

- Wing hyaline, unmodified (Fig. 1 c); CuAx ratio <0.7.................................... S. flavifemoratus sp. nov.

4 All femora with at least some brown cuticle; postpedicel elongate, triangular and tapering gradually.................. 5

- Femora I and II yellow, and only femur III with brown cuticle distally; postpedicel various.......................... 6

5 Both tibiae I and III with white cuticle and short ivory colored vestiture; tibia II yellow with brownish vestiture (Fig. 4 a); cer- cus elongate and projecting well beyond surstylus (Fig. 4 b).................................... S. eboritibia sp. nov.

- Tibia I only with white cuticle and ivory colored vestiture; tibia II yellow and tibia III brownish (Fig. 1 a); cercus and short and digitiform, not extending beyond surstylus (Fig. 1 b)............................................ S. tenorio sp. nov.

6 Vein M apically bent and forming sharp point on wing margin (Fig. 3 a); tibia III entirely yellow; postpedicel gradually taper- ing; tibia and tarsus I with ivory colored vestiture; cercus flagellate with long setae (Fig. 3 b)........ S. divericatus sp. nov.

- Vein M and R4+5 subparallel and wing margin entire; tibia III with some brown cuticle; other features various........... 7

7 Tibia I with normal short black vestiture; segment 7 (hypopygial peduncle) elongate, almost twice length of epandrium (Fig. 3 c), cercus elongate and clavate with subapical field of strong pale setae (Fig. 3 d).................... S. zurqui sp. nov.

- Tibia I with some ivory colored vestiture, segment 7 subequal in length to epandrium; cercus elongate with only short pale setae............................................................................................... 8

8 Tibia I only with ivory-colored vestiture on anterior face; tibia III with brown cuticle only on distal quarter (Fig. 2 a), surstylus squarish with long dorsoapical projection (Fig. 2 b).......................................... S. emusorum sp. nov.

- Femur, tibia and tarsus I almost entirely covered with short ivory-colored vestiture; tibia III with brown cuticle on basal quarter and distal quarter (Fig. 2 c), surstylus elongate and curved (Fig. 2 d)............................. S. naranjensis sp. nov.