Indocloeon (Indocloeon) secundum, Kluge & Suttinun, 2020

Kluge, Nikita J. & Suttinun, Chanaporn, 2020, Review of the Oriental genus Indocloeon Müller-Liebenau 1982 (Ephemeroptera: Baetidae) with descriptions of two new species, Zootaxa 4779 (4), pp. 451-484 : 456-467

Indocloeon (Indocloeon) secundum sp. n.

( Figs 1–3, 6–14, 25–34, 40–47, 53–55)

Indocloeon primum: Kluge 2012: 367 (partim).

Etymology. This is the second species of Indocloeon s. l. in Sri Lanka and the second known species of Indocloeon s. str.

Material examined ( ZIN). Holotype: L-S-I ♂ {specimen [XVI] (16) 2020}, SRI LANKA, Central province , Nuwara Elya District , foot of the mountain Sri Pada , Delhausie, river Seethagangula close to guesthouse «Vegetable Garden», 6°49’34”N 80°31’29”E, 4–5.II.2020, coll. N. Kluge & L. Sheyko : Paratypes: the same locality, date and collectors, 2 L-S-I ♂, 1 L-S/I ♂, 2 L-S ♂, 8 L-S-I ♀, 5 larvae; the same locality and collectors, 24–26.I.2011: 1 ♀ imago .

Descriptions. Larva. CUTICULAR COLOURATION. Cuticle of head mostly light brownish. Pronotum and mesonotum light brownish, with diffusive lighter and darker markings; mesonotum with diffusive darker wide longitudinal median stripe; protoptera with darker and lighter stripes along some longitudinal veins. Thoracic pleura from brown to nearly colourless, sterna lighter. Legs lighter or darker brownish. All abdominal terga I–X nearly uniformly brown. Abdominal sterna lighter than terga. Caudalii nearly uniformly brown.

Hypodermal colouration. Each abdominal tergum can have more or less expressed reddish transverse band on posterior margin.

Shape and setation. Antenna: anterior side of flagellum with pointed denticles at apex of each segment, without enlarged spines (as in Fig. 68). Dorsal side of labrum with paired row of setae stretching from submedian seta to anterolateral margin and including two setae between submedian seta and submarginal setal arc ( Fig. 6) [see Indocloeon s. str. (1)]. Left mandible: incisor terminated by 3 denticles with 2nd denticle longest; kinetodontium terminated by 3 denticles with 1st denticle longest; setae between prostheca and mola absent; mola with seta(e) on proximal angle ( Fig. 1) [see Indocloeon s. str. (2), (3), (4)]. Right mandible: incisor terminated by 3 denticles with 2nd denticle longest [see Indocloeon s. str. (2)]; kinetodontium terminated by 3 denticles with 1st denticle longest; margin between prostheca and mola with tuft of setae; mola with seta(e) on proximal angle ( Fig. 2). Maxillary palp long and slender, indistinctly 3-segmented, with remnant of 3rd segment very short and bent inward (as in Fig. 5) [see Indocloeon s. str. (5)]. Labial palp with 2nd segment moderately long, 3rd segment short; projected medioapical angle of 2nd segment sharply pointed ( Figs 3, 7) [see Indocloeon s. str. (7)]. Legs slender, with femur parallel-sided; in holotype, length of femur: tibia: tarsus: claw (mm) of fore leg 0.83: 0.55: 0.57: 0.15, of middle legs 0.92: 0.67: 0.47: 0.15, of hind leg 0.94: 0.67: 0.47: 0.15. Stout setae on outer side of femur non-pectinate, apically blunt (as in Fig. 81). Apex of femur normally with 2 (occasionally up to 4) stout blunt setae ( Figs 13–14). Tibiae of fore, middle and hind legs normally with one stout outer-apical seta (occasionally 2 such setae), without other stout setae on outer margin ( Figs 12–14) [see Indocloeon s. str. (8)]. Claw with 2 rows of denticles; in each row 3–4 most distal denticles larger than others ( Figs 10–11). Hind margin of tergum I either lacks denticles or with few occasional small denticles ( Fig. 25); hind margin of each tergum II–VII bears regular row of denticles fused at their proximal halves ( Figs 26–28); denticles on terga VIII–IX either non-fused, or partly fused at bases; on middle of posterior margin of tergum IX (behind submedian pair of setae) denticles shorter ( Fig. 29); denticles on tergum X non-fused ( Fig. 30). Hind margins of sterna I–II lack denticles; each sternum III–VIII with fused denticles ( Fig. 32); sternum IX of female bears non-fused or partly fused denticles; sternum IX of male bears non-fused or partly fused denticles at sides of protogonostyli and between protogonostyli. Scales on abdominal terga and sterna pointed, forming irregular transverse rows ( Fig. 34). Each segment of cercus with regular row of short denticles and few elongated spine-like denticles, especially expressed on each 2nd or each 4th segment ( Fig. 33). For other characters see diagnoses of Indocloeon s. str. above and Indocloeon s. l. ( Kluge 2012 and above).

Subimago. CUTICULAR COLOURATION. Cuticle nearly completely colourless, only margin of scutellum and femur-tiba articulations tinged with brownish ( Fig. 42). Postsubalar sclerite colourless, with antero-dorsal angle stretched and curved and postero-dorsal angle stretched into long projection (as in Kluge 2012: fig. 34) [see Indocloeon s. str. (12)]. Wings light.

Hypodermal colouration. As in imago (see below).

Male imago ( Fig. 41). Head pale (ocher or white). Antenna: scapus without hypodermal pigmented spots; proximal part of pedicellus with hypodermal pigmented spots on lateral and median sides (as in Fig. 35) [see Indocloeon s. str. (9)]. Turbinate eyes with facetted surface and distal part of stem pale yellowish; middle part of stem grayish, proximal part black. Thorax entirely pale (ocher or white), with few small brown markings. Legs pale ocher. In holotype, length of femur: tibia: tarsomeres (mm) of fore leg 1.00: 1.25: 0.05: 0.52: 0.37: 0,20: 0.14 (in subimago 0.83: 0.80: 0.05: 0.30: 0.22: 12: 14), of middle leg 0.92: 1.00: 0.21: 0.08: 0.04: 0.14 (same in subimago), of hind leg 0.94: 0.98: 0.21: 0.08: 0.04: 0.14 (same in subimago). Wings with longitudinal veins light brownish, only junction of Sc, RA and costal brace tinged with brown, cross veins contrastingly coloured with dark brown; pterostigma with 3–6 oblique cross veins; marginal intercalaries long. Abdominal segments I–VII translucent and whitish, with dark lateral tracheal trunks; each tergum II–VII with contrasting red or brown hypodermal narrow transverse stripe on posterior margin, laterally these stripes pointed and not reaching tracheal trunks; tergum VIII reddish medially, with white lateral parts; segments IX and X whitish [see Indocloeon s. str. (10), (11)]. Genitals whitish. Cerci whitish.

Genitals ( Fig. 46): Styliger medially with sharply outlined concavity [see Indocloeon s. str. (13)]. Proximal (1st+2nd) segment of gonostylus greatly widened at base, with inner margin evenly convex. Distal (3rd) segment of gonostylus with outer side convex and inner side straight or slightly concave.

Female imago ( Figs 42–45). Head and thorax pale (ocher or white); antennae as in male; pronotum with one pair of contrasting brown or reddish maculae. Legs pale ocher or diffusively tinged with reddish or yellowish. Wings as in male. Abdominal segments I–VII pale ocher, with dark lateral tracheal trunks and following hypodermal colouration: each tergum II–VI with contrasting red or brown narrow transverse stripe on posterior margin, laterally these stripes are pointed and do not reach tracheal trunks [see Indocloeon s. str. (11)]; each tergum III–VI, besides transverse stripe, with median longitudinal red or brown stripe, either parallel-sided ( Fig. 42), or triangular, widened posteriorly ( Figs 43–44); tergum VII whitish, with posterior margin narrowly bordered by red or brown; tergum VIII reddish medially, with whitish lateral parts; tergum IX whitish; tergum X ocher with reddish.

Egg. Oval, about 0.15 mm length. Polar area bearing net-like relief [see Indocloeon s. str. 15)] with cells wide, each with irregular convexities on bottom ( Fig. 55); sharply outlined cavities (see ibid.) located all over remaining part of egg ( Figs 53–54).

Dimension. Fore wing length (and approximate body length) 5–6 mm.

Habitat. Larvae of I. (I.) secundum sp. n. were collected in the same area as I. (I.) primum (village Delhausie near Sri Pada), but mainly in another biotope: all larvae of I. (I.) secundum sp. n. were collected in the river Seethagangula, while most larvae of I. (I.) primum were collected in a very small stream running from the forest through tea plantation. In the river Seethagangula, larvae of I. (I.) secundum sp. n. are found on sandy substrate in the widened places with stagnant water.

Comparison. In contrast to I. (I.) primum , the larva of I. (I.) secundum sp. n. has less elongated glossae and paraglossae; its 2nd segment of labial palp is less elongated and more widened from base to apex ( Fig. 3); denticles on hind margins of abdominal terga are shorter and less fused together, being mostly non-fused at least on tergum IX, sometimes also on tergum VIII ( Figs 26–30); scales on abdominal terga and sterna are pointed ( Figs 34) (in contrast to all other species of Indocloeon s. l.); cerci have elongated spine-like denticles ( Fig. 33). In contrast to I. (I.) primum , male imago of I. (I.) secundum sp. n. has cross veins contrastingly pigmented ( Fig. 41); female imago and subimago each have a median reddish stripe on abdominal terga III–VI ( Figs 42–44). The proximal (1st+2nd) segment of the gonostylus is more widened proximally, with its inner margin evenly convex ( Fig. 46–47). The egg of I. (I.) secundum sp. n. differs in the structure of the cell of the reticulate area (cells are wide, with convexities on bottom) ( Fig. 55) and by having more regular concavities on the remainder of the surface ( Fig. 53).

Distribution: Sri Lanka.