Caenis Stephens, 1835

Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2023, Contribution to the knowledge of family Caenidae (Insecta: Ephemeroptera) from Madurai District, Tamil Nadu, Zootaxa 5258 (1), pp. 39-75 : 73

Key to the known males of Caenis Stephens, 1835 from South India

(Male adult characters of Caenis sp. 2 is unknown)

1 Base of the antennal flagellum well dilated ( Fig. 101 )...................................... C. arunachalami sp. n.

- Base of the antennal flagellum slightly or not dilated ( Fig. 23 ).................................................. 2

2 Forceps apically with few tuft of short spines ( Srinivasan et al. 2023; Fig. 46 )........................... C. americani

- Forceps apically with a rigid spine ( Figs. 27 , 67 , 106 , 147 ).................................................... 3

3 Foretarsus segments 2–3 each with a lateral and a median projections and segment 4 with an apico-median projection ( Fig. 146 )....................................................................................... Caenis sp. 1

- Foretarsus segments 2–4 each with an apico-median projection................................................. 4

4 Prosternal sclerite bell-shaped ( Fig. 24 )....................................................... C. kaegies sp. n.

- Prosternal sclerite differently shaped ( Figs. 62 , 103 ).......................................................... 5

5 Forceps apically with a short spine ( Fig. 10 ).................................................... C. maduraiensis

- Forceps apically with a long spine ( Fig. 66 )................................................................ 6

6 Hind margin of penis with a well-developed medial incision ( Fig. 67 )......................... C. venkataramani sp. n.

- Hind margin of penis with slight or no medial incision ( Srinivasan et al. 2023; Fig. 10 )............................. 6

7 Forceps more or less parallel-sided ( Srinivasan et al. 2023; Fig. 11 )........................................ C. limai

- Basal half of forceps very broad, apical part abruptly narrowed ( Malzacher 2015; Fig. 5b )................... C. maratha

Figures

FIGURES 100–103. Male imago of Caenis arunachalami sp. n.: (100) dorsal view; (101) head, dorsal view; (102) foretarsus; (103) prosternal triangle.

FIGURES 20–23. Male imago of Caenis kaegies sp. n.: (20) dorsal view; (21) lateral view; (22) abdominal terga; (23) head, dorsal view.

FIGURES 45–47. Larval exuvia of Caenis kaegies sp. n.: (45) hindleg; (46) hindtarsus setation; (47) hindclaw.

FIGURES 24–27. Male imago of Caenis kaegies sp. n.: (24) prosternal triangle; (25) foretarsus; (26) male genitalia; (27) forceps.

FIGURES 64–67. Male imago of Caenis venkataramani sp. n.: (64) foretarsi; (65) closer view of foretarsomere segment III; (66) male genitalia; (67) forceps and penis.

FIGURES 104–106. Male genitalia of Caenis arunachalami sp. n.: (104) dorsal view; (105) penis; (106) forceps.

FIGURES 143–147. Male imago of Caenis sp. 1: (143) dorsal view; (144) closer view of abdominal terga; (145) head, dorsal view; (146) foretarsus; (147) forceps.

FIGURES 58–63. Caenis venkataramani sp. n.: (58) dorsal view of male imago; (59) closer view of head and thorax of male imago; (60) abdominal terga of male imago; (61) head, dorsal view of male imago; (62) prosternal triangle of male imago; (62) prosternal triangle of female imago.

FIGURES 8–15. Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021: (8) male imago (holotype); (9) head of male imago; (10) forceps; (11) forefemur of larval exuvia; (12) hindfemur of larval exuvia; (13) hindclaw; (14) sternum IX of male larval exuvia; (15) shagreen field in the dorsal surface of sternum IX.

FIGURES 4–7. SEM view of eggs of Caenis americani Srinivasan et al. 2021: (4) entire view; (5) epithemata; (6) closer view of chorion; (7) micropyle.