Indocloeon (Hindocloeon), 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 : 452-453

Genus Indocloeon Müller-Liebenau 1982 , s. l.

Hierarchical name: Indocloeon /g1 (incl. Hindocloeon subgen. n.).

( Figs 1–118)

Indocloeon Müller-Liebenau 1982: 125 (larva); Kluge 2012: 362 (larvae, subimagines, imagines); Kaltenbach & Gattolliat 2017: 57 (larvae).

Type species: Indocloeon primum Müller-Liebenau 1982 .

Comments. Indocloeon belongs to the plesiomorphon Protopatellata Kluge & Novikova 2011. All examined species of Indocloeon s. l. have leg structure characteristic for Protopatellata: patella-tibial suture is clearly expressed on middle and hind legs of larvae, subimagines and imagines of both sexes, but is completely absent on fore legs of all stages, including larva, female subimago and female imago ( Figs 13–14, 76–77; Kluge 2012: figs 13–14).

Indocloeon s. l. is characterized by a unique autapomorphy in the structure of male gonostyli ( Figs 46–49, 101– 105; Kluge 2012: fig. 23–25, 27–29, 32, 33): the proximal (1st+2nd) segment of the gonostylus is unusually short, and the distal (3rd) segment of the gonostylus is unusually long. In the subimago, the distal segment is nearly as long as it is in the imago stage, but is developed under the larval cuticle without crumpling ( Kluge 2012: fig.35). In the mature male larva, subimaginal gonostyli developing under larval cuticle are folded as follows: 2nd segment bent laterally; 3rd segment bent medially and curved anteriorly ( Kluge 2012: fig. 35). This mode of folding corresponds to the « Cloeon - type » which is usual for Protopatellata, but it looks unusual due to the fact that the 2nd segment is very short and the 3rd segment is very long.

Characters of larva. In the larval stage, Indocloeon s. l. is characterized by a certain combination of characters, which include plesiomorphies and characters of unclear status occurring in some other taxa. To the characters formerly reported ( Kluge 2012: pp. 362–363), the following additions, corrections and notes should be added.

MAXILLA. Kaltenbach and Gattolliat (2017) reported that maxillae of two species described by them have «two simple, robust apical setae under crown» (i.e. setae just ventrad-laterad of canines) and «medially with one spine-like seta and five long, simple setae» (i.e. setae proximad of biting edge). These characters are unclear in the original description of I. indonesiae , because the maxilla is figured in dorsal view ( Kluge 2012: fig. 5), while these setae are located on its ventral side. Kaltenbach and Gattolliat (2017) erroneously figured these setae on the same side as dentisetae, i.e. on the dorsal side of the maxilla ( Kaltenbach & Gattolliat 2017: figs 2h, 4g). Actually these setae are present in all examined species— I. (Indocloeon) primum , I. (Indocloeon) secundum sp. n., I. (Hindocloeon) indonesiae and I. (Hindocloeon) continentale sp. n. ( Fig. 69) and should be regarded as common for all Indocloeon s. l.

LABIUM. Using the terms suggested for setal rows on the labium ( Kluge 2016), the labium of Indocloeon s. l. should be characterized as follows ( Figs 7–9, 73–75): The glossa has the median longitudinal setal row, the dorsolateral longitudinal row, the ventro-median longitudinal row and scattered setae on the proximal part of the ventral side; the apex of the glossa bears 3–4 stout, long setae tightly pressed together. On the apex of the paraglossa, the latero-apical setae are arranged in 3 rows. The ventro-median row of setae runs obliquely and crosses the ventral side of the paraglossa from its median margin to the lateral margin ( Figs 9, 75). The dorso-median row of setae is restricted by the distal part of the paraglossa and passes along its median margin; it consists of 2 setae in Indocloeon s. str. and 4–5 setae in Hindocloeon ; laterad of this row, several thinner setae are located irregularly ( Figs 8, 74). Kaltenbach and Gattolliat (2017: figs 2i, 4h) erroneously figured the ventro-median row on the dorsal side of paraglossa and the dorso-median row on the ventral side of the paraglossa.

LEGS. Outer side of femur bears small, stout setae situated irregularly; these setae were said to be bipectinate and pointed both in I. primum and I. indonesiae ( Kluge 2012) ; actually, in I. (I.) primum , as well as in I. (I.) secundum sp. n., I. (H.) spathasetis and I. (H.) continentale sp. n., setae on the outer side of the femur are non-pectinate and apically blunt ( Fig. 81), and only in I. (H.) indonesiae and I. (H.) timorense are setae on outer side of the femur pectinate and pointed. Stout setae on the inner side of the femur are more or less pectinate and pointed in all known species. In the original descriptions of I. spathasetis and I. timorense , exact numbers of stout setae are reported ( Kaltenbach & Gattolliat 2017); however, their number and position significantly vary on individual legs of the species examined.

The apex of the femur normally bears 2 stout and blunt apical setae ( Figs 13–14, 76–77); on individual legs of I. (I.) primum and I. (I.) secundum sp. n., the femur bears not two, but a greater number of such apical setae (up to 8); such increased number of apical setae can be found on the selected leg of any pair—fore, middle of hind ones.

At least on the fore leg, the tibia normally bears one constant stout outer-apical seta and no other stout setae on outer margin ( Fig. 76); in the subgenus Indocloeon s. str., tibiae of middle and hind legs have the same setation of outer margins ( Fig. 14); in the subgenus Hindocloeon , tibiae of middle and hind legs bear an indeterminate number of smaller stout setae on the outer margin, among which the most distal one can be either somewhat larger than others ( Fig. 77) or equal to others ( Kluge 2012: fig. 14); thus, we can say that in the subgenus Indocloeon s. str. all tibiae have the constant outer-apical seta, and in the subgenus Hindocloeon only the fore tibia has the constant outer-apical seta. Within the subgenus Indocloeon , both in I. (I.) primum and I. (I.) secundum sp. n. tibiae of individual legs (belonging either to the fore, or to the middle pair) have not one, but two subapical setae ( Figs 12–13), and rarely a greater number of subapical setae (up to 5). The condition with two outer-apical setae was erroneously reported as a generic character ( Müller-Liebenau 1982: p. 126).

Characters of subimago. Subimagines of all Indocloeon s. l. have the cuticle nearly completely colourless ( Fig. 42). In the subimago of both sexes, all tarsomeres of all three leg pairs are covered by pointed microlepides only (in contrast to other parts of the leg, which are covered by microtrichiae) (probably plesiomorphy within Liberevenata).

Other characters of winged stages. Winged stages of all known Indocloeon s. l. have the tarsus of middle and hind legs as long as about ½ of the tibia length, with the proximal (1st+2nd) tarsomere relatively long and with the inner-apical spine occurring on the 3rd tarsomere only ( Kluge 2012: fig. 19). Wings have no more than one marginal intercalary per space ( Kluge 2012: figs 18, 37) (plesiomorphy, in contrast to Baetovectata).

Distribution. Oriental Region: known from Southern India ( I. continentale sp. n.), Sri Lanka ( I. primum and I. secundum sp. n.), Indochina ( I. continentale sp. n. and I. sp. « Vietnam »), Philippines ( I. longistylus ), Borneo ( I. spathasetis ), Java and Lesser Sunda Islands ( I. indonesiae and I. sp. «Java») and Timor Island ( I. timorense ).