Caenis ulmeriana Malzacher, 2015

Srinivasan, Pandiarajan, Sivaruban, Thambiratnam, Barathy, Sivaruban & Isack, Rajasekaran, 2024, New findings of the Caenis ulmeriana-group (Ephemeroptera: Caenidae) in the Western Ghats, India, Journal of Insect Biodiversity and Systematics 10 (3), pp. 443-451 : 444-447

Caenis ulmeriana Malzacher, 2015 ( Figs 1–28)

Material examined. One male mature larva ( AMC /ZN/279) and two female larvae ( AMC /ZN/280), India, Tamil Nadu, Theni district, Anai Pillayar Kovil Dam , 10°03′07″N, 77°34′02″E; 336 m . a.s.l., 23-XII-2020, leg. P. Srinivasan & R. Isack .

Distribution. The species is reported from India (new record), Java ( Malzacher, 2015), Sumatra ( Malzacher, 2015), Thailand ( Malzacher, 2015; Malzacher & Sangpradub, 2021), Myanmar ( Malzacher, 2023) and Philippines ( Malzacher, 2023) ( Fig. 28).

Diagnostic characters. Caenis ulmeriana can be distinguished from all other Caenis species by the following combination of characters: Imago (Imaginal characters extracted from the male last instar larva): base of antennal flagellum not dilated ( Fig. 2); prosternal triangle forming cone-shaped structure ( Fig. 3); foretarsus segments 2–4 each with a lateral and median projections ( Fig. 4); penis broad and rounded, ventral fold forming a semicircular or semielliptical process ( Fig. 5); forcipes moderate, straight, sides apically converging with a rigid elongated spine or a moderate spine equipped with an apical tuft of long spines ( Fig. 6).

Larva. Genae slightly bulged; pronotum and mesonotum denticulate without any nose-shaped projection ( Fig. 13); maxillary palp segment III clearly longer than segment II ( Fig. 10); ratio of labial palp segments 2 and 3 greater than 2 ( Fig. 12); forefemur with a transverse row of 8–10 conspicuous spatulate setae ( Fig. 15); foreclaw slender with 2–3 small basal denticles ( Fig. 17); midclaw bowed with 3–5 small basal denticles ( Fig. 19); hindclaw strongly bent with 2–3 basal denticles, and a dense row of microdenticles ( Fig. 22); dorsal surface of tergalius II with numerous scales and 2–5 spatulate setae on the apical 2/3 rd of Y-shaped ridge ( Fig. 23); hind margin of tergum VII and VIII with long, simple setae, and hind margin of tergum IX and X with small denticles ( Fig. 26).

Ecology. The larvae of Caenis ulmeriana were collected in Anaipillayar dam of the southern Western Ghats (3–5 m wide, 0.5–1 cm depth). The water temperature ranges between 24–26°C; pH 7–7.2. Substratum is mainly made of rock, cobbles, gravel and leaf litter ( Fig. 27).