Holotype : larva (slide 672, mounted with Canada balsam), Sri Lanka, border of Central and Sabaragamuwa provinces, vicinity of Marathenna village, mountain slope, helocrene in valley of large stream, 6.751333, 80.686167, 1390 m a.s.l., Chertoprud M.V. leg., 5.ii.2017 – IN Sri1Ingsp. Paratypes: 1 larva (slide 673, mounted with Canada balsam), ibid., Chertoprud M.V. leg., 5.ii.2017 – IN Sri1Ingsp. 1 larva (in slide 674 with Euparal), Sri Lanka, Central Province, vicinity of Holmwood Estate, stream (section with almost no current), 6.826389, 80.724444, 1660 m a.s.l., Chertoprud M.V. leg., 4.ii.2017 – IN Sri2Ingsp.

This species is named after Dr Mikhail V. Chertoprud (Moscow, Russia), who provided the material for this study.

Indoganodes tschertoprudi sp. nov. can be distinguished from the only other known representative of Indoganodes, I. jobini, by the following combination of characters: (i) tarsal claw with row of 5–8 large, blunt denticles and several (1–3) small, pointed denticles among the large ones (Fig. 3G, H); (ii) several distinct small chalazae bearing stout setae present only in distal part of inner margin of hind femur (Fig. 3C, F); (iii) shape of femora (Fig. 3A–C); (iv) posterolateral processes present only on segments VI–IX, all of them moderately developed (Fig. 5B); (v) posterior margins of all abdominal terga without any median tubercles (Fig. 5A).

Larva: body length 8.7–12.5 mm; caudal filaments partially detached, their length ratio to body unknown, paracercus not rudimental. Body light brown (Fig. 1B); head with yellow spots with unclear margins under ocelli; pronotum and mesonotum with several brown smudges (Fig. 1F); legs light brown; ventral side of body dirty yellow to light brown, without any distinct coloration.

Head. Genae small; head without any protuberances; surface of head covered with small hair-like setae and small scale sockets (Fig. 1C); anterior margin of clypeus with dense irregular row of long, stout, hair-like setae with divided apex (Fig. 1A). Labrum (Fig. 2A): wide, anterolateral angles rounded; anterior margin with shallow and wide medial emargination. Dorsal surface (especially anterior part) and anterior margin of labrum densely covered with differently sized (mostly medium-sized and long), thin and stout, hair-like setae. Mostly posterior part of dorsal surface of labrum densely covered with scale sockets. Lateral margins of labrum subparallel, slightly concave. Mandibles (Fig. 2C, D): surface covered with empty scale sockets and scattered short, thin, hair-like setae. Outer margin of mandibles with numerous short and medium-sized hair-like setae. Outer and inner incisors on both mandibles divergent. The molar surface of left mandible composed of three distinct, short, wide ridges; molar surface of right mandible composed of six distinct elongate ridges. Left mandible with bunch of long, hair-like setae under mola; right mandible without setae under mola. Hypopharynx (Fig. 2B): superlinguae with rounded apexes covered by thin and stout, mostly long, hair-like setae; apex of lingua densely covered with short, fine setae. Lingual surface near base with irregular (subparallel to longitudinal axis of body) rows of short, pointed, stout setae (about 18 setae on each side). Maxilla (Fig. 2E, F): palp reduced to small knob, with short, hair-like seta on apex; galea-lacinia with two dentisetae with bristly apexes; galea-lacinia bears one apically rounded, robust denticle on inner margin above dentisetae, ventral surface of maxilla near robust denticle with group of 6 long, stout, hair-like setae; also group of long, stout setae on inner margin near inner dentiseta; base of galea-lacinia with group of long, stout, hair-like setae near inner margin; one or two short or long, pointed, stout setae on dorsal surface near reduced palp. Labium (Fig. 2G): glossae and paraglossae deeply divided, their apexes bluntly pointed, outer margins of paraglossae with deflection. Surfaces of glossae and paraglossae covered with stout and thin, mostly long, hair-like setae; prementum covered with scattered hair-like setae; submentum well developed, covered by same setae and additionally by empty scale sockets. Labial palp 3-segmented; segments II and III robust, but not flattened. Outer margin and adjacent area of dorsal surface of segments I and II covered with long, thin and stout, hair-like setae and several empty scale sockets; several long, hair-like setae on inner margin of segments I and II. Segment III elongated, rounded apically; length/width ratio 2.43–2.75; apex of segment with numerous fine setae, several fine setae present on segment’s surface.

Thorax. Dorsal surface covered with short, thin, hair-like setae and scattered empty scale sockets; tubercles and ridges absent (Fig. 1E). Anterolateral angles of pronotum with small protuberances (Fig. 1F); prosternum without bilobular, spinous process medially (Fig. 1D).

Femora of all legs robust, with longitudinal ridge; outer margin without apical projections (Fig. 3A–C). Fore femur 1.73–2.05 times as long as wide; middle femur 2.27–2.37 times as long as wide; hind femur 2.31–2.58 times as long as wide. Average length ratios of femur, tibia, and tarsus: fore leg 2.13 : 2.24 : 1.00; middle leg 2.78 : 2.85 : 1.00; hind leg 3.48 : 3.51 : 1.00.

Dorsal surface of fore femur with indistinct wide, transversal band of short and medium-sized, oval, stout setae bearing feathered margins and short and medium-sized, feathered, stout setae with divergent margins and cleft at apex (Figs 3A, D, E, 4A–C). Same kind of setae along outer margin and on outer and inner margins (on outer margin, setae more numerous then on inner margin); one stout setae on inner margin on small chalaza. Outer margin of fore femur without chalazae. Entire dorsal surface of fore femur and its margins covered with scattered short, thin, hair-like setae and long, pointed, stout setae with feathered margins.

Ventral surfaces of fore tibia and tarsus with numerous differently shaped, stout setae on inner margin and along it; main types of stout setae are: long, stout setae with feathered margins and pointed apex (Fig. 4G); feathered, stout setae with divergent margins and flat apex (some setae with cleft at apex) (Fig. 4F); medium-sized, stout, hair-like setae (Fig. 4H); elongated, feathered, stout setae with slightly divergent margins and rounded apex (Fig. 4E). Dorsal surface of fore tibia and tarsus covered with medium-sized, hair-like setae; dorsal surface of fore tibia along patella-tibial suture also bears row of differently sized, oval or rounded, feathered, stout setae with cleft at apex in some (Fig. 4A–D). Outer margins of fore tibia and tarsus without stout setae, and only with differently sized, hair-like setae.

Dorsal surfaces of middle and hind femora covered with oval and rounded, medium-sized, feathered, stout setae with cleft at apex in some (Fig. 4B, D), and scattered, short and medium-sized, feathered, stout setae with divergent margins, with cleft at apex (Fig. 4J), and short and medium-sized, oval, stout setae with feathered margins (Fig. 4A–C). Stout setae mostly along outer margin and in central area of femora; stout setae more numerous on outer margins than on inner margins. Additionally, entire dorsal surface and all margins of middle and hind femora covered with a few short, hair-like setae. Middle femur with small, indistinct chalazae bearing stout setae on inner margin (Fig. 3B). Several distinct, small chalazae bearing stout setae present only in distal part of inner margin of hind femur (Fig. 3C, F).

Patella-tibial suture on tibiae of middle and hind legs distinctly shorter than that on fore leg. Setation of middle and hind tibiae and tarsi near that of fore leg, but in contrast to fore leg, outer margins of these tibiae bear short, feathered, oval, stout setae; in immature larvae, row of stout setae more dense and distinct.

Tarsal claw of all legs robust, hooked, its surface covered with several medium-sized, thin, hair-like setae. Claw with row of 5–8 large, blunt denticles and several (1–3) small, pointed denticles among the larger ones (Fig. 3G, H).

Abdomen. All terga without any median tubercles (Fig. 5A). Terga I–X covered with: short, feathered, stout setae with divergent margins and a cleft at apex; mostly short, thin, hair-like setae; empty scale sockets (Fig. 4I–K). Posterior margins of all terga without denticles, only with a few short, thin, hair-like setae. Lateral margins of terga I–V covered only with scattered thin, hair-like setae; lateral margins of segments VI–X also with short, feathered, stout setae. Posterolateral processes presented on segments VI–IX; all of them moderately developed; largest processes on segments VI–IX (Fig. 5B, C). All sterna covered with: short, feathered, thin hair-like setae (Fig. 4N); short setae with divergent, feathered margins, and feathered apex (Fig. 4L, M); empty scale sockets.

Segment I without gills; gills present on abdominal segments II–VI (Fig. 5A). Gill II light brown (Fig. 5D), covered with scattered short, thin, hair-like setae and empty scale sockets; dorsal lamella semi-operculate, without transverse band of weakened membrane, incompletely covers other gills. Ventral lobes of gills II–V bifurcated, multifoliate (Fig. 5D–G); gill VI simple, without medial cleft (Fig. 5H).

Basal part of caudal filaments with feathered, stout setae and stout, hair-like setae at articulations; stout setae shorter, mainly oval on dorsal side of the filaments and elongated on ventral side.

Winged stages : unknown.

Larvae of new species were found in wooded gullies in the mountains of Sri Lanka in the subtropical altitudinal zone (altitude 1390–1660 m a.s.l.) (Fig. 6A). Two larvae of I. tschertoprudi sp. nov. were collected from a helocrene spring in the valley of a large stream (Fig. 6B). The maximum depth of the spring was only 1–2 cm deep; there was no current and the bottom was covered with mud, leaf litter, and detritus. Co-occurring species of mayflies recorded from this habitat were Ephemera sp. (Ephemeridae) and Kimminsula sp. (Leptophlebiidae). Another larva of this new species was collected along with Ephemera sp. from a small stream, in a section with almost no current and having a muddy bottom (Fig. 6C).