taxonID	type	description	language	source
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	description	(Figs. 1 – 32)	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	materials_examined	Materials examined. Holotype. L-S-I ♂, South India, Tamil Nadu, Madurai District, Karuppaurani pond, 9 ° 94 ' 07 " N, 78 ° 18 ' 84 " E, 132 m, 27. I. 2025, colls. M. Kiruthiga & P. Srinivasan (AMC / ZN / 289). Paratypes. 3 L-S ♂, 3 L-S-I ♀, 7 larvae (AMC / ZN / 290) with same label data as holotype. Other materials. 5 ♀ imagos, South India, Tamil Nadu, Madurai District, Karuppaurani lake, 9 ° 94 ' 07 " N, 78 ° 18 ' 84 " E, 132 m, 24. V. 2020, colls. P. Srinivasan & R. Isack (AMC / ZN / 266).	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	diagnosis	Diagnosis. Caenis srinii sp. nov. can be distinguished from all other Caenis species by the following combination of characters: Imago: 1) base of the antennal flagellum not dilated (Fig. 2); 2) prosternal triangle with concave sides, tip less broadly rounded lacking a transverse strip (Fig. 3); 3) Segments 2 – 4 of foretarsus with a small lateral and a median projection (Fig. 5); 4) penes broad with a deep concavity at the posterior margin and each of the two lobes triangular (Fig. 7); 5) forceps divergent, apically with a large spine equipped with 4 – 5 small spines (Fig. 7). Larva: 1) cuticular coloration of each femora ochre with contrasting dark brownish patch in the 3 / 4 the distal apex; tibia and tarsus ochre with dark brownish band at middle (Fig. 17); 2) medial margin with a triangular process between mola and inner incisor of right mandible (Fig. 12); 3) mesonotum with margins denticulate without any bulging (Fig. 16); 4) forefemur with a transverse row of 8 – 10 spatulate setae on ¾ of distal region (Fig. 18); 5) hindclaw strongly bent with 4 basal denticles increasing in size distally, and a row of microdenticles (Fig. 21); 6) gill cover with poorly developed Y-shaped ridges, inner one reduced posteriorly (Fig. 24); 7) hind margin of sternum IX rounded with numerous minute indentations medially (Fig. 26).	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	description	Description Male imago (Fig. 1). Measurements (holotype). Body length: 2.41 mm; forewing length: 1.67 mm; foreleg length: 1.99 mm; midleg length: 0.9 mm; hind leg length: 1.2 mm; cercus length: 6.7 mm. Ratios. Head (see Malzacher 2015; Fig. 4 k), c: a = 2.2, a: b = 1.3; Leg: fore femur: fore tibia = 0.44; fore tibia: fore tarsus = 1.47; fore leg: hind leg = 1.7; segments of fore tarsus 1 st: 2 nd: 3 rd: 4 th: 5 th = 1: 2.1: 1.4: 1.2: 1.3. Coloration. Head: Vertex with dark brown transverse bands between the ocelli (Fig. 2). Antenna: scape and pedicel pale. Thorax: Pronotum with a dark brownish transverse band near the posterior margin. Mesonotum dark brownish with lateral stripes; scutellum pale; mesonotal suture darkly pigmented. Wings: Mostly hyaline except costa and subcostal veins reddish-brown. Legs: Forefemora dark brown, proximal and distal ends of foretibiae with dark brown patches, remaining parts pale or translucent (Fig. 4). Abdomen: Terga I – II often with a faint blackish stippling, other segments of tergum mostly colourless. Cerci translucent. Morphology. Head. Anterior margin between lateral and frontal ocelli slightly bowed (Fig. 2). Pedicel ca. 2.5 times the length of scape. Base of the antennal flagellum not dilated (Fig. 2). Thorax. Prosternal triangle with concave sides, tip less broadly rounded lacking a transverse strip (Fig. 3). Segments 2 – 4 of foretarsus with a small lateral and a median projection (Fig. 5). Abdomen. Tergum II without a finger-like process. Lateral processes absent. Sternum IX and genitalia as in Fig. 6. penes broad, nearly as wide as the styiger plate (Fig. 7); penis with a deep concavity at the posterior margin and each of the two lobes triangular. Styliger sclerite broad, with short apophyses. Forceps moderate, divergent, apically with a large spine equipped with 4 – 5 small spines (Fig. 7). Female imago (Fig. 8). Measurements (n = 3). Body length: 3.5 – 3.8 mm; forewing length: 2.3 – 2.5 mm. Coloration similar to that of males, but terga III – VI with well-developed dark brownish transverse band (Fig. 8). Mature larva (Fig. 9). Measurements (n = 2). Body length: 3.4 – 3.6 mm in female (Fig. 9); 2.4 – 2.7 mm in male (Fig. 10). Caudal filaments length: 2.5 – 2.8 mm in female; 1.3 – 1.5 mm in male. Antennae length: 1.5 mm. Head. General coloration dark brown, with a dark brownish transverse band between lateral ocelli; vertex with branch-like markings (Fig. 9). Pedicel 2.5 times length of scape (Fig. 11) and with few simple setae on lateral margins, genae distinctly bulged. Mouthparts: Labrum ca. twice as broad as long, medial emargination with thick setae, lateral margin with long simple setae. Hypopharynx with few small, hair-like setae on apical margin and lateral margins of superlingua with long, simple setae. Right mandible. Outer incisor with three denticles and inner incisor with two denticles; medial margin between mola and inner incisor with a small triangular process (Fig. 12). Left mandible. Outer incisor with four denticles and inner incisor with three denticles; medial margin without any process between mola and incisors (Fig. 13). Maxilla (Fig. 14). Palp three-segmented with a ratio of 1: 0.6: 1.2; segment I with a row of four pointed bristles on outer margin; segment III with a longitudinal row of long, simple setae near inner marginal surface. Labium (Fig. 15). Palp three-segmented with length ratio of 1: 0.9: 0.4; segment I with a row of 6 bipinnate bristles on outer margin, segment II with a row 5 pointed bristles on outer margin, segment III with a row of 6 spine-like setae on inner margin and two transverse rows of long, spine-like setae along with few scattered long, hair-like setae on the dorsal surface. Thorax. Mesonotum with margins denticulate without any bulging (Fig. 16). Legs: Cuticular coloration (Fig. 17): Femur of each leg ochre with contrasting dark brownish patch in the 3 / 4 the distal apex; tibia and tarsus ochre with dark brownish band at middle. Coxal processes semi-circular with denticulate margins. Foreleg (Fig. 17): lengths of femur: tibia: tarsus: claw 0.41: 0.35: 0.26: 0.14 mm; femur with a transverse row of 8 – 10 spatulate setae on ¾ of distal region (Fig. 18); femora covered with numerous scale bases; inner margin with a row of long hair-like setae on proximal half; dorsal surface of tibia with a longitudinal row of 6 – 8 spatulate setae; tarsi with a row of 2 bipinnate bristles; claw thin and slender with 3 basal denticles, increasing in size distally (Fig. 19). Midleg (Fig. 22): lengths of femur: tibia: tarsus: claw 0.42: 0.32: 0.23: 0.12 mm. Dorsal surface of femur with scattered spatulate bristles (Fig. 22); outer margin with a row of few long, spatulate setae; tibia similar to that of foreleg, except inner margin medially with a large spine-like seta; tarsi with a longitudinal row of 6 bipinnate bristles and a long monopectinate seta on distal end; midclaw (Fig. 20) broad with 5 basal denticles. Hindleg (Fig. 23): lengths of femur: tibia: tarsus: claw 0. 46: 0.39: 0.24: 0.14 mm. Femur, tibia, and tarsi similar to that of midleg. except outer margin medially with a large spatulate seta; claw strongly bent with 4 basal denticles increasing in size distally, and a row of microdenticles (Fig. 21). Abdomen. Abdominal terga with dark brownish sublateral patches (Fig. 9). Tergum I without any posteromedian process; tergum II with a blunt triangular posteromedian process; gill cover with poorly developed Y-shaped ridges, inner one reduced posteriorly (Fig. 24); dorsal surface with 2 – 3 spatulate setae on apical half of Y-ridge (Fig. 24); left margin of Y-ridge with a row of long, simple setae; right margin of Y-ridge with a row of small, simple setae. Microtrichia elongated, parallel-sided, and pinnate. Gills III – VI with numerous filaments (Fig. 25). Posterolateral processes on terga I and II absent; tergum III with slightly developed posterolateral processes; terga IV – IX with a well-developed posterolateral processes. Hind margins of tergum VII with a row of long hair-like setae and tergum VIII with a row of long hair-like setae along with few spatulate setae and terga IX and X with small denticles. Hind margin of sternum IX rounded with numerous minute indentations medially (Fig. 26), shagreen field of sternum IX with 9 – 10 irregular rows of very small denticles parallel to the hind margin (Fig. 27). Cerci translucent. Gill cover about 2.5 times the length of gill I. Egg. Oval, relatively long and broad with 110 – 120 μm in length; 75 – 85 μm in width (Fig. 29). Two-surfaced chorion with a tiny protuberance on the outer edge of the egg nearest to the polar cap and a perfectly smooth surface on the pole (Fig. 30). One end has a polar cap, while the other is smooth and devoid of any attaching structures (Fig. 29). A polar cap with numerous coiled threads located close to the margin with the chorion in their extended configuration, the Knob terminated coiled threads (KCT’s) in their folded configuration appear as a compact button-like structure (Figs. 30 – 32). The micropyle has a tubular micropyle canal and circular sperm guide in the subequatorial region (Fig. 28).	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	etymology	Etymology. The new species is named after Dr. Pandiarajan Srinivasan (Sri S. Ramasamy Naidu Memorial College, Sattur) for his invaluable contribution to the study of Caenidae in India. Noun in the genitive case.	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
03C98115FF93FFE9FF45FD5245BDFE2D.taxon	distribution	Distribution. Karuppaurani pond, Madurai, Tamil Nadu, India.	en	Kiruthiga, Mahendran, Sivaruban, T., Jeyapriya, Velmurugan, Barathy, S., Isack, Rajasekaran (2026): A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Madurai, India. Zootaxa 5782 (1): 183-192, DOI: 10.11646/zootaxa.5782.1.11, URL: http://dx.doi.org/10.7717/peerj.20736
