Caenis sp. 1

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 : 67-69

Caenis sp. 1

( Figs. 143–151 )

Materials examined. 1J imago, 1♀ imago, South India, Tamil Nadu, Madurai District, Vaigai river , 10°08′32′′N, 77°93′22′′E, 192 m, 1.VIII.2022, colls. P. Srinivasan & R. Isack ( AMC /ZN/211, 212) .

Description.

Male imago ( Fig. 143 ). Measurements. Body length: 2.9 mm; forewing length: 1.9 mm; foreleg length: 1.8 mm; midleg length: 1 mm; hindleg length: 1.2 mm; cercus length: 6.7 mm. Ratios. Head (see Malzacher 2015; Fig. 4k ): c: a = 2.2; a: b = 1.1; Leg: fore femur: fore tibia = 0.57; fore tibia: fore tarsus = 1.37; fore leg: hind leg = 1.5; segments of fore tarsus 1st: 2nd: 3rd: 4th: 5th = 1: 3.6: 2.1: 1.6: 0.9

Coloration. Head: Vertex light brownish. Antenna: scape and pedicel pale. Thorax: Prothorax mostly pale with dark brownish transverse band in the posterior margin. Mesonotum generally dark brownish; scutellum darkly pigmented with fin-shaped processes; mesonotal suture darkly pigmented; prosternum, mesosternum, and metasternum pale. Wings hyaline, costa, and subcostal veins reddish-brown. Legs whitish, except apical part of femora and tibiae with a dark brownish patch. Abdomen: Terga mostly colourless with a well-developed brownish transverse band and a longitudinal black stripe medially on terga III– VI ( Fig. 144 ). Cerci translucent.

Head ( Fig. 145 ). Fore margin between lateral and frontal ocelli slightly bowed. Pedicel two times the length of scape. Base of the antennal flagellum slightly dilated.

Thorax. Prosternal sclerites strong, forming an apically blunt isosceles triangle, without transverse strip. Foretarsus segments 2–3 each with a lateral and a median projections and segment 4 with an apico-median projection equipped with strong small spines ( Fig. 146 ).

Abdomen. Tergum II without a finger-like process. Lateral filaments short. Penis broad, with rounded lobes, hind margin with a well-developed medial incision, Penis mediolaterally with a tongue-shaped process. Forceps basally broadened with more or less parallel sides, consists of a long tuft of spines with a strong spine more or less fused with few thin spines ( Fig. 147 ). Other genital details are missing.

Female imago. Measurements. Body length: 3.7 mm; forewing length: 2.4 mm.

Coloration is similar to that of males. Transverse band in terga III–VI strongly pronounced compared to that of males.

Larva. Unknown.

Egg. Length: 110–120 μm; width: 75–85 μm. Oval-shaped ( Figs. 148, 149 ); chorion smooth with a flat epithema forming a coil of fine threads on the pole ( Fig. 150 ); micropyle long, situated at the subequatorial plane with mouth not broadened, with well visible circular sperm guide ( Fig. 151 ).

Distribution. Vaigai river, Madurai, Tamil Nadu, India.

Discussion. The unnamed species Caenis sp. 1 is similar to C. ulmeriana and C. limai by the shape of the forceps, but differs from them by the lateral and median projections in foretarsus segments 2–3 and an apico-median projection in segment 4 in the male imago ( Malzacher 2015; Malzacher and Sangpradub 2020; Srinivasan et al. 2023). The eggs of Caenis sp. 1 distinguished from both C. ulmeriana and C. limai by the length of the micropyle (Malzacher and Sangpradub 2020; Srinivasan et al. 2023).

Figures

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 148–151. SEM view of eggs of Caenis sp. 1: (148, 149) entire view; (150) epithema; (151) micropyle.

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.