Branchiobaetis javanicus (Ulmer, 1913), comb. nov., by present designation.

New combinations

1. Branchiobaetis javanicus (Ulmer, 1913), comb. nov.

2. Branchiobaetis sabahensis (Müller-Liebenau, 1984), comb. nov.

New species from Sumatra

3. Branchiobaetis aduncus sp. nov.

4. Branchiobaetis hamatus sp. nov.

5. Branchiobaetis joachimi sp. nov.

6. Branchiobaetis minangkabau sp. nov.

New species from the Philippines

7. Branchiobaetis jhoanae sp. nov.

Larva. This new genus is distinguished by a combination of the following characters: A) body elongate and slender (Figs 24a, 25b); B) antennal scape distally with short, stout setae (Fig. 15i); flagellum with basal segments parallel sided and thereafter inclined, giving the impression of a spiral arrangement (Fig. 5a); C) labrum subrectangular, dorsally with a pair of long, simple submedian setae and a submarginal arc of long, simple setae (Fig. 14a); D) right mandible with blade-like incisor, prostheca stick-like with distolateral dentation (Fig. 6b); E) left mandible with blade-like incisor, prostheca robust, distally with denticles and comb-shape structure (Fig. 6a); F) maxillary palp 2-segmented, apex of segment II pointed; with accessory gill outside laterally between stipes and cardo (Figs 1a, 18h–j); G) labium with glossae basally broad, narrowing towards apex, shorter than paraglossae; paraglossae laterally slightly undulated, distally truncate and slightly bent inwards; labial palp with small to medium protuberance at segment II (Fig. 14j); H) femora with stout setae both on anterior and posterior side, dorsal margin with row of medium to long, spine-like setae and straight row of medium, fine setae (Figs 3a, b, 15a, d); claw robust, pointed, with one row of denticles and usually a long, subapical seta (Figs 7k, 15e); femoral patch reduced on fore and middle legs, well developed on hind legs (Fig. 7d–i); I) finger-like accessory gill ventrally between coxa and prosternum (Fig. 1b); J) hind protoptera present, well developed; K) paraproct with spines at posterior margin (Fig. 15h); L) seven pairs of tergalii (abdominal gills) on segments I–VII, anal margin with alternate short and long, fine setae (Fig. 15g); M) subimaginal gonostyli developing under cuticle of last instar larvae folded in the following way: segment II sharply bent towards middle, last segment sharply bent laterally (Figs 4a–d, 10a, b).

Imago. Forewing with double intercalary veins longer than the distance between corresponding longitudinal vein; pterostigma with numerous cross veins (Fig. 9a, c). Hind wing with three longitudinal veins and well developed triangular costal projection (Fig. 9d, e). Imaginal gonostyli: segment I of gonostylus with projected blunt angle proximad of its middle; segment III short and triangular (Fig. 10d, e). Sterno-styligeral muscle present and thin (Fig. 10f).

The imago is known for a single species (B. javanicus comb. nov.). Therefore, it is unclear, which of its characters are species-specific and which can be considered as diagnostic for the new genus. The structure of hind wing and the presence of a thin sterno-styligeral muscle are also revealed for B. sabahensis comb. nov., based on details developing in last instar larvae.

Branchiobaetis is a combination of Branchio-, in reference to the Latin word for gills and the accessory gills of the larvae, and baetis, to highlight the similarities with the genus Baetis. The gender is masculine.

Larva.

Head. Antenna. Bases of antennae not close to each other, without carina between them. Scape at least distally (and often outside laterally) with short, stout, apically rounded setae (Fig. 15i); flagellum with basal segments parallel sided and thereafter inclined, giving the impression of a spiral arrangement (Fig. 5a).

Labrum (Fig. 14a). Subrectangular, wider than long. Distal margin with medial emargination and a small process. Dorsally with a pair of long, simple, submedian setae and on each side a submarginal arc of long, stout, simple setae; surface scattered with medium, simple setae. Ventrally with lateral row of medium, simple setae, anterolaterally with long, feathered setae on margin and medially with long, bifid, pectinate setae on margin, several small, stout setae near anterolateral and sometimes also lateral margin.

Right mandible (Figs 6b, 14b–d, 22b). Incisor and kinetodontium almost fused, incisor with denticles, outer denticle blade-like, kinetodontium with denticles; inner margin of innermost denticle of kinetodontium with row of thin setae; prostheca stick-like, distolaterally denticulate; apex of mola with tuft of feathered setae. Basal half with fine, simple setae scattered over dorsal surface.

Left mandible (Figs 6a, 18e, f). Incisor and kinetodontium fused, incisor with denticles, outer denticle blade-like, kinetodontium with denticles; prostheca robust, distally denticulate and with comb-shape structure; apex of mola without tuft of setae. Basal half with fine, simple setae scattered over dorsal surface.

Incisors of both mandibles are quickly worn after the larva started feeding and become much shorter than in fresh, unused mandibles. The real shape of unused mandibles can be seen during development inside the actual mandible (Figs 6a, b, 20b, d).

Maxilla (Figs 1a, 18h–j). Apically with three stout canines and three denti-setae; distal denti-seta tooth-like, other denti-setae slender, bifid, and pectinate; maxillary palp with two segments, apex strongly pointed. Small accessory gill located on outer side of the articulation between stipes and cardo.

Hypopharynx (Fig. 14h). Apex with compact tuft of long, dense setae-like processes.

Labium (Fig. 14j). Glossae basally broad, narrowing towards apex, shorter than paraglossae; inner margin with row of spine-like setae, increasing in length distally; apex with several short to long, robust setae; outer margin with row of spine-like setae; ventral surface with fine, simple scattered setae. Paraglossae laterally slightly undulated, distally truncated, and slightly bent inwards; apex with three rows of long, robust, distally pectinate setae; ventrally usually with several short, simple setae in distomedial area and one short, simple seta in proxolateral area; dorsally with few long, spine-like setae near inner margin. Labial palp with three segments, segment II with small to medium protuberance.

Thorax. Hind protoptera present, well developed.

Foreleg (Figs 1b, 2a–c, 3a, b, 7a, d, g, k, 13a, 15a, d, e). Femur with row of medium to long, spine-like setae and additionally straight row of fine setae on dorsal margin; on apex short, stout setae on anterior and posterior side; femoral patch present, reduced and sometimes indistinct. Accessory gill on inner side of coxal articulation (between coxa and prosternum); bubble-like membranous swelling between coxa and trochanter and between coxa and pleurite (Figs 1b, 2a–c). Tibia with long patella-tibial suture in ¾ area; dorsal margin with row of short, stout setae and row of fine setae. Tarsus dorsally with row of short, stout setae, ventrally with row of curved, spine-like setae increasing in length distally. Claw robust, pointed, with one row of denticles; usually with one long, subapical seta (posterior seta sensu Kluge and Novikova 2014).

Middle and hind leg (Figs 2a, 7b, c, e, f, h, i). As foreleg; femoral patch on middle leg also reduced, but well developed on hind leg; hind femur without apical setae on posterior side. Bubble-like membranous swelling on middle leg between coxa and trochanter and reduced between coxa and pleurite, on hind leg only between coxa and trochanter.

Figure 2. 

Branchiobaetis javanicus comb. nov., larva a thorax, lateral view. Branchiobaetis joachimi sp. nov., larva b, c foreleg. Abbreviations: cx, coxa; ff, forefemur; hf, hind femur; mf, middle femur; pl, pleurite; pr, pronotum; tr, trochanter.

Abdomen. Tergalii (Figs 15g, 26a–e). Present on abdominal segments I–VII, dorsolaterally oriented; costal margin with minute denticles and short, fine setae; anal margin with minute denticles and alternating both short and long, fine setae.

Paraproct (Fig. 15h). Posterior margin with stout spines; most species with short, stout, apically rounded setae near posterior margin. Cercotractor with numerous, small, marginal spines.

Figure 3. 

Branchiobaetis javanicus comb. nov., larva a dorsal margin of foreleg. Branchiobaetis joachimi sp. nov., larva b dorsal margin of foreleg.

Caudalii (Fig. 5e). Inner lateral margin of cerci and paracercus bilaterally with primary swimming setae.

Larval protogonostyli (Fig. 10a) slightly projected; subimaginal gonostyli developing under cuticle of last instar larvae folded in the following way: segment II sharply bent towards middle, last segment sharply bent laterally (Figs 4a–d, 10a, b).

Imago. Forewing with double intercalary veins longer than distance between corresponding longitudinal vein; pterostigma with numerous cross veins (Fig. 9a, c). Hind wing with three longitudinal veins and well developed triangular costal projection (Fig. 9e). Imaginal gonostyli: segment I of gonostylus with projected blunt angle proximad of its middle; segment III short and triangular (Fig. 10d, e). Sterno-styligeral muscle clearly developed, but thin (Fig. 10f).

The imago is known from a single species (B. javanicus comb. nov.). Therefore, it is unclear, which of its characters are species-specific and which are generic (e.g., shape of turbinate eyes). Ulmer (1913, 1924) and Müller-Liebenau (1981) described imago and subimago and a complementary description is given below under B. javanicus comb. nov.

(Figs 27–29). Indonesia (Sunda Islands, Kalimantan), Malaysia (Sabah), Philippines.

Type locality. Indonesia • W. Java, Gedeh, Tjibodas; 1400 m; 24.-30.XII.1930; leg. M. A. Lieftinck; 2 ♀ larvae on slides; ZMH • Java, Cibodas; 6–11.VIII.2009; leg. N. Kluge & L. Sheyko; 4 ♂ subimagos with associated larval exuviae; [III](2)B2009, [III](7)B2009; 73 larvae; slides 7.XII.2021-1, 11.XII.2021-1, 24.XII.2021-1, 24.XII.2021-2, 24.XII.2021-3, 17.XII.2021-1; SPbU. Other material. Indonesia • Java, vic. Bogor, Mt. Sulak, Chiapus; 06°39'29"S, 106°44'55"E; 624 m; 24.II.2008; leg. S. Melnitsky; 1 ♂ imago; SPbU • Lombok, Mount Rinjani National Park; 25.IX.2009; leg. N. Kluge & L. Sheyko; 1 ♀ imago with associated larval and subimaginal exuviae; [XXXIX](1)2009; 34 larvae; SPbU • Java, Bogor, Ciliwung River, downstream of botanical garden; 06°35'32"S, 106°48'00"E; 235 m; 01.V.2010; leg. J.-M. Elouard; 1 larva on slide, GBIFCH00592476, 1 larva in alcohol, GBIFCH00592468; MZL • Java, Malang Batu Jalang, cascade, forest river; 07°54'52"S, 112°35'05"E; 570 m; 09.V.2010; leg. J.-M. Elouard; 2 larvae in alcohol, GBIFCH00592466, GBIFCH00592467; MZL.

Indonesia • Sumba, forest stream; 09°38'37"S, 119°40'56"E; 470 m; 27.IX.2011; leg. M. Balke; larva on slide; GBIFCH00592481; MZL; larva in alcohol; GBFCH00592463; MZL • Sumbawa, Batu Dulang, 10 mins to Tepal, forest stream; 08°35'52"S, 117°16'41"E; 860 m; 16.IX.2011; leg. M. Balke; 2 larvae on slides; GBIFCH00592479, GBIFCH00592480; MZL; 39 larvae in alcohol; GBIFCH00592462, GBIFCH00975593, GBIFCH00975594, GBIFCH00975604, GBIFCH00975605; MZL • Bali, Ubud, Sayan, Ayung River; 08°29'59"S, 115°14'35"E; 194 m; 20.IX.2011; leg. M. Balke; larva on slide; GBIFCH00592477; MZL • Bali, Ubud, Monkey River; 08°31'10"S, 115°15'18"E; 260 m; 16.V.2010; leg. J.-M. Elouard; larva on slide; GBIFCH00592478; MZL; 2 larvae in alcohol; GBIFCH00975611; MZL • Sumatra Barat, Universitas Andalas campus, forest stream; 00°54'40"S, 100°28'23"E; 360 m; 08.XI.2011; leg. M. Balke; 3 larvae on slides; GBIFCH00592474, GBIFCH00592475, GBIFCH00592502; MZL; 69 larvae in alcohol; GBIFCH00592489, GBIFCH00592501; GBIFCH00975582, GBIFCH00975583, GBIFCH00975595, GBIFCH00975596, GBIFCH00975597, GBIFCH00975603; MZL • Flores, Maumere region, river in garden land; 08°42'55"S, 124°04'24"E; 134 m; 21.IV.2012; leg. M. Balke; 2 larvae on slides; GBIFCH00592262, GBIFCH00592297; MZL; 18 larvae in alcohol; GBIFCH00592264, GBIFCH00592265, GBIFCH00975606; MZL.

Figure 4. 

Branchiobaetis gen. nov., subimaginal gonostyli developing under cuticle of male last instar larva a B. javanicus comb. nov. b B. sabahensis comb. nov. (not yet fully developed) c B. aduncus sp. nov. d B. joachimi sp. nov.

Larva. Following combination of characters distinguish B. javanicus comb. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with triangular protuberance, segment III rather long (Müller-Liebenau 1981: fig. 1b); B) dorsal margin of fore femur with row of spine-like setae, basally dense and partly arranged in double row (Fig. 7a; Müller-Liebenau 1981: fig. 1k); C) posterior margin of tergite I smooth, without spines; posterior margins of tergites II–X with triangular spines, partly longer than wide (Fig. 7j), partly as long as wide; posterior margin of sternites: I–VI smooth, without spines; VII smooth or with few small spines; VIII with few spaced, small, blunt spines; IX with triangular spines; D) paraproct not expanded, with stout setae along posterior margin.

Figure 5. 

Branchiobaetis javanicus comb. nov., exuviae of last instar male larva a portion of antenna b head c enlarged right eye and precursor of turbinate eye d left half of pronotum and mesonotum e abdomen.

Imagos and subimagos are described by Ulmer (1913, 1924). Müller-Liebenau correctly reported that hind wing has not two, but three veins (Fig. 9e; Müller-Liebenau 1981: fig. 2b). Larva is described by Ulmer (1939); larval characters are illustrated by Müller-Liebenau (1981: fig. 1). Here we give additional figures of larvae (Figs 1a, b, 3a, 5a–7k), subimagos (Fig. 8a–h), male imago (Figs 9a, b, j, 10d–f) and female imago (Fig. 9c–g, k).

Figure 6. 

Branchiobaetis javanicus comb. nov., larva a, b apices of left and right mandibles with mandibles of next instar developing inside them.

Turbinate eyes. Ulmer (1913, 1924) reported only colour of turbinate eyes (brown-grey), but not their shape. Turbinate eyes of male imago and subimago unusually small, cylindrical, with facetted surfaces round; facetted surface with approx. ten facets in diameter (Fig. 9b). In last instar male larva, precursors of the turbinate eyes representing a pair of reddish-brown maculae of egg-like shape; at middle of this macula, a smaller round area with well-expressed facets, approx. ten facets in diameter; peripheral area of the macula consists of very small and indistinct facets (Fig. 5c). Facetted surface of subimago and imago is developed from the round area, but not from the whole reddish brown macula.

Figure 7. 

Branchiobaetis javanicus comb. nov., larva a–c fore, middle, and hind legs d–f femoral patch of fore, middle and hind legs g–i femoral patch of fore, middle and hind legs j abdominal tergum k claw.

Larval mandibles (Fig. 6a, b). Incisors of left and right mandibles very long and parallel-sided (i.e., blade-like), with rounded apex and two small pointed denticles in proximal half.

N.B. Such shape of mandibular incisors is only visible when they are developed inside mandibles of the previous instar (Fig. 6a, b) and possibly just after the moult, before the mandibles are hardened and the larva starts to eat. After feeding, the incisors are worn and sometimes broken, so look much shorter (see outer lines of the same figures). Such worn mandibles are figured by Müller-Liebenau (1981: fig. 1e).

Maxillary and sternal gills (Fig. 1a, b). Presence of small ventral tracheal gills not formerly reported. Presence of a pair of maxillary gills and a pair of fore coxal gills.

Figure 8. 

Branchiobaetis javanicus comb. nov., subimagines a–g female subimaginal exuviae a foreleg, anterior view b fore femur, posterior view c, d base of fore tibia, anterior and posterior view e middle tibia f left mesopleuron with prealar and postsubalar sclerites g right part of mesonotum h middle tarsus of male subimago. Arrows show apex of patella-tibial suture.

Each maxillary gill located on outer side of articulation between stipes and cardo; trachea penetrating into this gill, arising from paired tracheal stem which is more distally divided into branch penetrating into maxilla and branch penetrating into corresponding half of labium (Fig. 1a).

Figure 9. 

Branchiobaetis javanicus comb. nov. a fore wing of male imago b head of male imago c, d fore and hind wing of female imago e hind wing enlarged f head and thorax of female imago g middle leg h, i male subimaginal abdomen extracted from larva j abdomen of male imago k abdomen of female imago.

Each fore coxal gill located on inner side of coxal articulation, i.e., on the membrane between coxa and prosternum; trachea penetrating into this gill, arising from trachea going into foreleg; close to its base, trachea is divided into branch passing inside prosternum and branch penetrating into gill. Inside fore coxal gill, trachea widened, thin-walled and colourless (Fig. 1b).

Patella-tibial suture. Patella-tibial suture present on all legs of larva, female subimago and female imago, including their fore legs (that is characteristic for Anteropatellata); greatly stretched along tibia: in larva reaching inner side of tibia in distal ¼ (Fig. 7a, c), in subimago and imago near middle of tibia (Figs 8a, e, 9g); in all stages patella-tibial suture barely reaching inner side of tibia, not crossing it.

Figure 10. 

Branchiobaetis javanicus comb. nov., male genitalia a subimaginal gonostyli crumpled under larval cuticle at earlier stage of development b subimaginal gonostyli extracted from larva starting to molt to subimago c genitalia of subimago, ventral view d genitalia of imago, ventral view e the same, apex of gonostylus f genitalia of imago, dorsal view. Abbreviations: gs1–gs3, segments of gonostyli; gv, gonovectis; m.gs, gonostylar muscle; m.sg, styligeral muscle; pgs, larval protogonostylus; usg, unistyliger.

Femoral patch. Each larval leg with a femoral patch/field of minute curved setae on inner side of femur near its base (that is characteristic of Baetofemorata); femoral patch on hind leg large (Fig. 7f, i), but on fore and middle legs either much smaller (Fig. 7d, e), or indistinct (Fig. 7g, h).

Figure 11. 

Branchiobaetis javanicus comb. nov., eggs.

Texture of subimaginal tarsi (Fig. 8c, d, h). In subimagos of both sexes, all tarsomeres covered with blunt microlepides; only very basal part of first tarsomere covered with microtrichia (like tibia), and apical parts of tarsomeres with pointed microlepides.

Colouration of subimaginal cuticle. Head colourless, antennae brown. Pronotum brown. Mesonotum mostly brown (Fig. 8g). Thoracic pleura with brown and colourless areas (Fig. 8f). Legs mostly light brownish with dark brown markings on femur, tibia, and tarsus (Fig. 8a–e). Abdominal terga nearly uniformly brown, slightly darker laterally; sterna lighter; cerci lighter brownish.

Colouration of abdomen of winged males. Abdominal colouration of male imago is adequately described by Ulmer (1913, 1924). It consists of contrasting colourless-white areas, vine-red areas and black areas, with sharply different colour patterns of the terga I–II, III–IV, V–VII, VIII–IX, and X, and sharply different colour patterns of the sterna I–IV, V–VII, VIII, and IX (Fig. 9j).

Abdominal colouration of subimago was briefly characterized by Ulmer (1924) as ‘Ähnlich der Imago, Segment III bis VII bräunlichgelb durchscheinend’. Among examined male subimagos reared from larvae or extracted from mature larvae, some individuals agree with this characteristic, i.e., their terga I–II and VIII–IX are dark brown, but terga III–VII and all sterna are uniformly light brownish (Fig. 9h); some individuals have terga and sterna III–VII differentiated somewhat approximating to that of imago (Fig. 9i).

Gonostyli of male. Imaginal gonostyli with characteristic species-specific shape (Fig. 10d, e; Ulmer 1924: fig. 25): unistyliger (wrongly called ‘Glied I’ in Ulmer 1924) cylindrical, somewhat narrowed at middle; segment I of gonostylus (wrongly called ‘Glied II’ in Ulmer 1924) with projected blunt angle proximad of its middle; segment III of gonostylus (wrongly called ‘Glied IV’ in Ulmer 1924) short and triangular, i.e., apically widened and truncate.

N.B. When developing subimaginal gonostyli are bent under the larval cuticle, segment II of gonostylus is bent medially (as in other Baetofemorata), and segment III is sharply bent laterally, that is a peculiar feature of Branchiobaetis gen. nov. (Fig. 10a, b). In subimago freed from the larval cuticle, gonostyli retain features of their previous pose under larval cuticle, with segments II sharply bent medially and segments III somewhat bent laterally (Fig. 10c); the species-specific shape of segment III is present in imaginal stage only (Fig. 10d, e). A paradoxical feature is that segment III starts to develop as unusually long (Fig. 10a), later it is bent and pressed to the 2^nd segment (Fig. 10b), while subsequently it becomes shorter (Fig. 10c, d).

Internal parts of male genitalia. Sterno-styligeral muscle developed, but slender; gonovectes S-shaped, i.e., arched, with apices curved cranially (Fig. 10f).

Egg (Fig. 11a–d). Eggs irregularly oval, with irregularly situated shallow cavities, and surface of chorion rugose.

Dimension. Size rather variable: fore wing length of male and female (and the general body length) varies from 6 mm to 10 mm; females usually larger than males.

Tergalii unable for rhythmical respiratory movements (as in other Baetungulata), and larvae are unable to live for a long time in stagnant water. Larvae are most abundant in fast streams with cold water.

(Fig. 27b). Indonesia: Java, Lombok; B. cf. javanicus comb. nov. Indonesia: Sumatra, Bali, Sumba, Sumbawa, Flores.

Malaysia • Sabah, Ranau; 14.–16.VII.1972; leg. G. F. Edmunds; ♂ larva on slide; SPbU • Sabah, Kundasang; 04.IX.1994; leg. S. C. Kang; ♂ larva on slide; SPbU.

Indonesia • East Kalimantan, Bas. Malinau, River Seturan, loc. Seturan (2000-block 44–45), trib. Wok (Sungai Guang); 2°59'12"N, 116°33'11"E; 16.VI.2000; leg. P. Derleth & J.-L. Gattolliat; 3 larvae on slides; GBIFCH00592470, GBIFCH00592471, GBIFCH00592495; larva in alcohol; GBIFCH00270724; MZL • East Kalimantan, Bas. Malinau, River Seturan, loc. Seturan (2001-block 57), trib. Bengahau; 02°59'22"N, 116°30'46"E; 19.VIII.2000; leg. P. Derleth & R. Schlaepfer; larva on slide; GBIFCH00592494; larva in alcohol; GBIFCH00270710; MZL • East Kalimantan, Bas. Malinau, riv. Seturan, loc. Seturan (2001-block 57), trib. Benganau; 02°59'22"N, 116°30'46"E; 11.IV.2001; leg. P. Derleth & B. Feldmeyer; larva in alcohol; GBIFCH00270710; MZL.

Figure 12. 

Branchiobaetis sabahensis comb. nov., larva a head of male larva b labrum c prosternum and bases of forelegs, front view d labium.

Larva. Following combination of characters distinguish B. sabahensis comb. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with short, thumb-like protuberance; segment III rather short and wide, ca. 0.5× length of segment II, ca. 0.8× as long as width at base, ca. 0.7× as long as maximal width (Fig. 12d; Müller-Liebenau 1984b: fig. 3b); B) incisor of right mandible with ventral denticle (Müller-Liebenau 1984b: fig. 3e; C) dorsal margin of femur with row of ca. 15 long, spine-like setae; no additional row of short setae along margin; no short, stout setae on surface of femur (Fig. 13a; Müller-Liebenau 1984b: fig. 3k); D) posterior margin of tergite I smooth, without spines; posterior margins of tergites II–III with rounded or triangular spines, posterior margins of tergites IV–X with triangular spines (Fig. 13c; Müller-Liebenau 1984b: fig. 14); posterior margins of sternites: I–V smooth, without spines; VI smooth, without spines, or with some small, triangular spines; VII–IX with triangular or blunt spines (Fig. 13d).

Figure 13. 

Branchiobaetis sabahensis comb. nov., larva a apex of hind femur b paraproct c abdominal tergum IX d abdominal sternum VIII e tergalius.

Imago. Winged stages unknown. Judging from details revealed in last instar larva, turbinate eyes not narrowed; hind wing with costal projection; sterno-styligeral muscle present and thin.

The original description of Baetis sabahensis Müller-Liebenau, 1984 was based on larvae, and certain similarities of this species with B. javanicus were reported. The single argument to separate B. sabahensis from B. javanicus, was the statement that ”Baetis sabahensis sp. nov. is the only species in the genus with coxal gills on the first pair of legs” (Müller-Liebenau 1984b: 92). Larva of B. javanicus was described and figured by the same author earlier (Müller-Liebenau 1981), but the coxal and maxillary gills had not been reported (see above).

Larva of Branchiobaetis sabahensis comb. nov. can be separated from B. javanicus comb. nov. by the following characters: A) dense spines on abdominal sternite VIII (Fig. 13d); B) presence of only one or two stout setae on paraproct, or complete absence (Fig. 13b); C) incisor of right mandible with ventral denticle; D) labial palp segment III short and wide (Fig. 12d; see above).

Judging by precursors of turbinate eyes developed in last instar male larva, male imago of B. sabahensis comb. nov. should differ from B. javanicus comb. nov. by usual (not narrowed) turbinate eyes (Fig. 12a).

Branchiobaetis cf. sabahensis comb. nov. Specimens from Indonesia (Kalimantan) always have a series of stout setae along posterior margin of paraproct, contrary to specimens from Malaysia (Sabah). As there are no other differentiating characters to B. sabahensis comb. nov. from Malaysia (Sabah), we treat this population as B. cf. sabahensis comb. nov., waiting for genetic investigation of fresh material in the future.

(Fig. 27b). Malaysia (Borneo: Sabah); B. cf. sabahensis comb. nov. Indonesia (Borneo: Kalimantan).

Holotype. Indonesia • Sumatra, volcano Singgalang, River Caruak; 00°23'03"S, 100°21'24"E; 1640 m; 23.III.2014, leg. M. Gueuning; larva on slide; GBIFCH00422219; MZL. Paratypes. Same data as holotype; 1 larva on slide; GBIFCH00422126; MZL; 4 larvae in alcohol; GBIFCH00422185, GBIFCH00422194, GBIFCH00422203, GBIFCH00422209; MZL. Indonesia • Aceh, Mt. Leuser area, Kedah rainforest lodge; 03°58'36"S, 97°15'17"E; 1300 m, 3.–12.X.2013, leg. M. Balke; larva on slide; GBIFCH00515622; MZB (temporarily housed in MZL) • Sumatra Barat, Talang, 20 km south of Solok; 00°52'52"S, 100°37'23"E; 650 m; 25.V.2010; leg. J.-M. Elouard; larva on slide; GBIFCH00592486; MZL.

Figure 14. 

Branchiobaetis aduncus sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d apex of right mandible e left mandible f left prostheca g apex of left mandible h hypopharynx and superlinguae i maxilla j labium (left: ventral view, right: dorsal view) k apex of paraglossa.

Larva. Following combination of characters distinguish B. aduncus sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with medium triangular protuberance, segment III apically rounded (Fig. 14j); B) incisor of right mandible with ventral denticle (Fig. 14b, d); C) dorsal margin of femur with row of medium, spine-like setae, basally longer and clavate; additional row of short, hook-like setae along margin (Fig. 15a–c); D) dorsal margin of tibia and tarsus with row of short, hook-like setae (Fig. 15a, c); E) posterior margin of tergites: I smooth, without spines; II–V rounded, wider than long; VI partly rounded, partly triangular; VII–IX triangular, narrower and longer towards last segment (Fig. 15f); posterior margins of sternites: I–VI smooth, without spines; VII–IX with small, spaced, triangular spines; F) paraproct with short, stout, apically rounded setae along posterior margin (Fig. 15h).

Figure 15. 

Branchiobaetis aduncus sp. nov., larva a foreleg b seta of femur basal dorsal margin c hook-like seta of leg dorsal margins d fore femur apex, posterior view e fore claw f tergum IV g tergalius IV h paraproct i base of antenna.

Larva (Figs 14, 15, 24a, 26a). Body length 7.0–8.1 mm. Caudalii broken. Antenna: ca. 2.5× as long as head length.

Colouration (Fig. 24a). Head, thorax, and abdomen dorsally brown, ventrally light brown. Femur light brown, apically and dorsally along margin dark brown, with large, distomedial, dark brown spot; tibia light brown, basally along patella-tibial suture darker, tarsus dark brown. Caudalii light brown, primary swimming setae dark brown.

Antenna (Fig. 15i). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 14a). Length 0.6× maximum width. Submarginal arc of setae composed of nine or ten long, simple setae.

Right mandible (Fig. 14b–d). Incisor blade-like with three denticles and a ventral denticle; kinetodontium with four denticles. Margin between prostheca and mola straight.

Left mandible (Fig. 14e–g). Incisor blade-like with four denticles; kinetodontium with three denticles. Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins slightly convex.

Hypopharynx and superlinguae (Fig. 14h). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 14i). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one pectinate, spine-like seta and six or seven medium, simple setae. Maxillary palp approx. as long as galea-lacinia; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Labium (Fig. 14j, k). Inner margin of glossa with ca. nine spine-like setae, increasing in length distally; apex with one long, one medium and one short, robust setae; outer margin with ca. nine spine-like setae; Paraglossa with three short, simple setae in anteromedial area and one in posterolateral area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I 1.1× length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with medium, triangular, distomedial protuberance; distomedial protuberance 0.5× width of base of segment III; ventral surface with short, fine, simple setae; dorsally with five or six spine-like setae near outer margin. Segment III apically rounded; length 0.8× maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 15a–e). Ratio of foreleg segments 1.3:1.0:0.5:0.2. Femur. Length ca. 3× maximum width. Dorsal margin with row of 6–9 medium, curved, spine-like setae and basally 10–12 longer, clavate setae. Additional row of short, stout, hook-like setae along dorsal margin. Apex rounded, with pair of spine-like setae; short, stout, hook-like setae on anterior and posterior side. Short, stout, apically rounded setae scattered along ventral margin. Tibia. Dorsal margin with two irregular rows of short, stout, hook-like setae. Surface with short, stout, hook-like setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout, hook-like setae and row of fine, simple setae. Claw with one row of ten or eleven denticles, distal denticle much longer than other denticles.

Terga (Fig. 15f). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergites: I smooth, without spines; II–V rounded, wider than long; VI partly rounded, partly triangular; VII–IX triangular, narrower and longer towards last segment. Posterior margins of sternites: I–VI smooth, without spines; VII–IX with small, spaced, triangular spines.

Tergalii (Figs 15g, 26a). Tracheae extending from main trunk to inner and outer margins; with light brown band along main trunk of tracheae on anal side. Tergalius I 2/3 as long as segment II, tergalius IV as long as length of segments V and 1/3 VI combined, tergalius VII as long as length of segment VIII.

Paraproct (Fig. 15h). Posterior margin with 12–16 stout spines. Short, stout, apically rounded setae near posterior margin. Surface scattered with scale bases, micropores and fine, simple setae.

Based on the Latin word aduncus, meaning hooked, with reference to the hook-like setae on the legs.

Indonesia: Sumatra (Fig. 28a).

The species was found at altitudes from 650 m to 1640 m, most specimens were collected in a forest stream with the following parameters: slope below 5%, width 1–3 m, depth 15–30 cm, velocity 0.2 m/s, water temperature 17 °C, pH 7, stream bed dominated by boulder, stones, and gravel.

Holotype. Indonesia • Sumatra, volcano Talamau; River Pularian; 00°00'60"N, 100°00'01"E; 960 m; 01.IV.2014; leg. M. Gueuning: larva on slide; GBIFCH00422261; MZL. Paratypes. Same data as holotype; 2 larvae on slides; GBIFCH00422231, GBIFCH00422242; 20 larvae in alcohol; GBIFCH00422233, GBIFCH00422252, GBIFCH00422267, GBIFCH00422276, GBIFCH00422355, GBIFCH00422359, GBIFCH00422445, GBIFCH00422748, GBIFCH00422753, GBIFCH00422798, GBIFCH00422843, GBIFCH00423022, GBIFCH00975634, GBIFCH00975635; MZL. Indonesia • Sumatra, volcano Singgalang, River Sianok; 00°19'57"S, 100°19'19"E; 1150 m; 24.III.2014; leg. M. Gueuning; 2 larvae on slides; GBIFCH00422184, GBIFCH00423074; 13 larvae in alcohol; GBIFCH00422123, GBIFCH00422167, GBIFCH00422206, GBIFCH004208, GBIFCH00422215, GBIFCH00422216, GBIFCH00422224, GBIFCH00422797, GBIFCH00422889, GBIFCH00422938, GBIFCH01115975, GBIFCH01116020; MZL.

Larva. Following combination of characters distinguish B. hamatus sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with medium, rounded protuberance, segment III apically slightly pointed (Fig. 16h); B) incisor of right mandible with ventral denticle (Fig. 16b); C) dorsal margin of femur with row of medium, spine-like setae, basally longer and clavate; additional row of short, hook-like setae along margin (Fig. 17a, b); D) dorsal margin of tibia and tarsus with row of short, hook-like setae (Fig. 17a, b); E) posterior margin of tergites: I smooth, without spines; II–IX triangular, narrower and longer towards last segment (Fig. 17e); posterior margin of sternites: I–VII smooth, without spines; VIII–IX with small, spaced, triangular spines; F) tergalius IV apically slightly concave (Fig. 17f); G) paraproct with short, stout, apically rounded setae along posterior margin (Fig. 17g).

Figure 16. 

Branchiobaetis hamatus sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d left mandible e left prostheca f hypopharynx and superlinguae g maxilla h labium (left: ventral view, right: dorsal view).

Larva (Figs 16, 17, 24b, 26b). Body length 6.8–8.5 mm. Cerci: broken. Paracercus: ca. 0.4× body length. Antenna: ca. 2.5× as long as head length.

Figure 17. 

Branchiobaetis hamatus sp. nov., larva a foreleg b hook-like seta of leg dorsal margins c fore femur apex, posterior view d fore claw e tergum IV f tergalius IV g paraproct h base of antenna.

Colouration (Fig. 24b). Head, thorax and abdomen dorsally brown, abdominal segment X light brown; head, thorax and abdomen ventrally light brown, scape with dark brown spot at inner lateral side. Femur light brown, apically and dorsally along margin dark brown, with large, medial, dark brown spot; tibia light brown, tarsus dark brown in distal half. Caudalii light brown, cerci darker brown in area of ca. ½ of length, paracercus darker brown parallel to cerci; primary swimming setae dark brown.

Precursors of turbinate eyes (Fig. 25c) in male last instar larvae representing a pair of subtriangular maculae; in the middle of this macula, a smaller, round, elevated area with well-expressed facets, approx. ten facets in diameter; peripheral area of the macula with indistinct facets.

Antenna (Fig. 17h). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 16a). Length 0.6× maximum width. Submarginal arc of setae composed of 7–10 long, simple setae.

Right mandible (Fig. 16b, c). Incisor blade-like with three denticles and a ventral denticle; kinetodontium with four denticles. Margin between prostheca and mola straight, with minute denticles.

Left mandible (Fig. 16d, e). Incisor blade-like with four denticles; kinetodontium with three denticles. Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins slightly convex.

Hypopharynx and superlinguae (Fig. 16f). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 16g). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one pectinate, spine-like seta and five or six medium, simple setae. Maxillary palp approx. as long as galea-lacinia; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Labium (Fig. 16h). Inner margin of glossa with 10–12 spine-like setae, increasing in length distally; apex with two long and one medium, robust setae; outer margin with six or seven spine-like setae; Paraglossa with two short, simple setae in anteromedial area and one in posterolateral area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I approx. as long as length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with medium, rounded, distomedial protuberance; distomedial protuberance 0.3× width of base of segment III; ventral surface with short, fine, simple setae; dorsally with 4–8 spine-like setae near outer margin. Segment III apically slightly pointed; length 0.8× maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 17a–d). Ratio of foreleg segments 1.3:1.0:0.5:0.2. Femur. Length ca. 3× maximum width. Dorsal margin with row of 7–9 medium, curved, spine-like setae and basally 10–15 longer, clavate setae. Additional row of short, stout, hook-like setae along dorsal margin. Apex rounded, with pair of spine-like setae; short, stout, hook-like setae on anterior and posterior side. Short, stout, apically rounded setae scattered along ventral margin. Tibia. Dorsal margin with two irregular rows of short, stout, hook-like setae. On surface short, stout, hook-like setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout, hook-like setae and row of fine, simple setae. Claw with one row of ten or eleven denticles, distal denticle much longer than other denticles.

Terga (Fig. 17e). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergites: I smooth, without spines; II–IX triangular, narrower and longer towards last segment. Posterior margin of sternites: I–VII smooth, without spines; VIII–IX with small, spaced, triangular spines.

Tergalii (Figs 17f, 26b). Tracheae extending from main trunk to inner and outer margins; with light brown band along main trunk of tracheae on anal side. Tergalius I 2/3 as long as segment II, tergalius IV as long as length of segments V and 1/2 VI combined, tergalius VII as long as length of segment VIII.

Paraproct (Fig. 17g). Posterior margin with 11–16 stout spines. Short, stout, apically rounded setae near posterior margin. Surface scattered with scale bases, micropores and fine, simple setae.

Based on the Latin word hamatus, meaning hooked, with reference to the hook-like setae on the legs.

Indonesia: Sumatra (Fig. 28a).

The specimens were collected in two sites at altitudes of 940 m and 1150 m, with following physical conditions: slope 5–10%, width of stream 3–8 m, depth 1–50 cm, velocity 0.5 m/s–0.7 m/s, pH 8, stream bed dominated by boulder, stones and gravel or stones and sand respectively. One of the sites was strongly influenced by human activities, with lot of waste and brown water.

Holotype. Indonesia • Sumatra, volcano Marapi, East; 00°21'33"S, 100°30'42"E; 1205 m; 03.IV.2014; leg. M. Gueuning; larva on slide; GBIFCH00422405; MZL. Paratypes. Same data as holotype; 19 larvae in alcohol; GBIFCH00422228, GBIFCH00422235, GBIFCH00422238, GBIFCH00422241, GBIFCH00422254, GBIFCH00422266, GBIFCH00422402, GBIFCH00422440, GBIFCH00422489, GBIFCH00422709, GBIFCH00422844, GBIFCH00422887, GBIFCH00422932, GBIFCH00422977; MZL. Indonesia • Sumatra, volcano Sago, River Kobun; 00°22'33"S, 100°39'33"E; 1095 m; 19.III.2014; leg. M. Gueuning; 2 larvae on slide; GBIFCH00592506, GBIFCH00592507; 22 larvae in alcohol; GBIFCH00422152, GBIFCH00422166, GBIFCH00422173, GBIFCH00422222, GBIFCH00422226, GBIFCH00422227, GBIFCH00422253, GBIFCH00422256, GBIFCH00422258, GBIFCH00422266, GBIFCH00422268, GBIFCH00422270, GBIFCH00422663, GBIFCH00422708, GBIFCH00422754, GBIFCH00422928, GBIFCH00422979, GBIFCH00423113; MZL • Sumatra, volcano Sago, River Tampo; 00°22'20"S, 100°41'45"E; 960 m; 20.III.2014; leg. M. Gueuning; 8 larvae in alcohol; GBIFCH00422232, GBIFCH00422239, GBIFCH00422249, GBIFCH00422250, GBIFCH00422255, GBIFCH00422265, GBIFCH00422619, GBIFCH00423112; MZL • Sumatra, volcano Sago, River Tampo; 00°20'37"S, 100°41'02"E; 1255 m; 21.III.2014; leg. M. Gueuning; 12 larvae in alcohol; GBIFCH00422230, GBIFCH00422236, GBIFCH00422237, GBIFCH00422243, GBIFCH00422251, GBIFCH00422264, GBIFCH00422883, GBIFCH00423026, GBIFCH00423068, GBIFCH00423116; MZL • Sumatra, volcano Sago, River Kaligain; 00°18'01"S, 100°40'08"E; 1040 m; 05.IV.2014; leg. M. Gueuning; 1 larva on slide; GBIFCH00592525; 22 larvae in alcohol; GBIFCH00422229, GBIFCH00422234, GBIFCH00422244, GBIFCH00422246, GBIFCH00422259, GBIFCH00422263, GBIFCH00422304, GBIFCH00422441, GBIFCH00422442, GBIFCH00422443, GBIFCH00422659, GBIFCH00975612, GBIFCH00975613; MZL • Sumatra, volcano Singgalang, River Airjernih; 00°24'07"S, 100°16'44"E; 840 m; 25.III.2014; leg. M. Gueuning; 1 larva on slide; GBIFCH00422159; 7 larvae in alcohol; GBIFCH00422052, GBIFCH00422142, GBIFCH00422157, GBIFCH00422160, GBIFCH00422618, GBIFCH00422752, GBIFCH00423024; MZL • Sumatra, volcano Singgalang, River Magyih; 00°23'33"S, 100°16'34"E; 845 m; 25.III.2014; leg. M. Gueuning; 1 larva on slide; GBIFCH00422211; 5 larvae in alcohol; GBIFCH00422081, GBIFCH00422154, GBIFCH00422198, GBIFCH00422201, GBIFCH00422217; MZL • Sumatra, volcano Singgalang, River Magyih; 00°22'50"S, 100°17'39"E; 1075 m; 26.III.2014; leg. M. Gueuning; 3 larvae in alcohol; GBIFCH00422098, GBIFCH00422168, GBIFCH00422221; MZL • Sumatra, volcano Singgalang, River Sianok; 00°19'57"S, 100°19'19"E; 1150 m; 24.03.2014; leg. M. Gueuning; 1 larva in alcohol; GBIFCH00422248; MZL.

Indonesia • Sumatra Barat, Bukit Barisan, above Padang, creek; 00°56'44"S, 100°32'44"E; 1047 m; 08.XI.2011; leg. M. Balke (UN3); 3 larvae on slides; GBIFCH00592472, GBIFCH00592473, GBIFCH00592505; 17 larvae in alcohol; GBIFCH00975598, GBIFCH00975599, GBIFCH00975602, GBIFCH00980897, GBIFCH00980898; MZL.

Larva. Following combination of characters distinguish B. joachimi sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with short, broad, rounded protuberance, with few small, stout, simple setae on protuberance; segment III apically rounded (Fig. 18k); B) dorsal margin of femur with row of medium, spine-like setae; many short, stout, apically rounded setae along dorsal margin; same type of setae scattered on surface and along ventral margin (Fig. 19a, c); C) posterior margin of tergites: I with triangular, pointed spines or short, triangular, blunt spines; II–IX with triangular, pointed spines, longer than wide (Fig. 19f); posterior margin of sternites: I–IV smooth, without spines; V with small, spaced, triangular spines; VI–IX with triangular spines; D) paraproct with short, stout, apically rounded setae along posterior margin (Fig. 19h).

Figure 18. 

Branchiobaetis joachimi sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d mola apex of right mandible e left mandible f left prostheca g hypopharynx and superlinguae h maxilla i apex of maxillary palp j accessory gill between stipes and cardo of maxilla k labium (left: ventral view, right: dorsal view).

Larva (Figs 18, 19, 24c, d, 26c). Body length 7.9–9.6 mm. Cerci: ca. 0.6× body length. Paracercus: ca. 0.6× cerci length. Antenna: ca. 2.5× as long as head length.

Figure 19. 

Branchiobaetis joachimi sp. nov., larva a foreleg b hook-like seta of femur apex c seta on ventral surface of femur d fore femur apex, posterior view e fore claw f tergum IV g tergalius IV h paraproct i base of antenna.

Colouration (Fig. 24c, d). Head, thorax and abdomen dorsally brown or grey-brown, with pattern as in Fig. 24c or 24d; head, thorax and abdomen ventrally light brown or light grey, abdominal segment IX laterally with dark brown streaks. Femur light brown or light grey, apically and dorsally along margin dark brown, with large, distomedial, dark brown spot; tibia light brown or grey, basally dark brown along patella-tibial suture; tarsus light brown or grey, dark brown in distal half. Caudalii light grey-brown, darker brown area on ca. ½ of cerci length; primary swimming setae dark brown.

Precursors of turbinate eyes in male last instar larvae representing a pair of brownish, egg-shaped maculae; in the middle of this macula, a smaller, round, elevated area with well-expressed facets, ca. 14 facets in diameter; peripheral area of the macula with indistinct facets (Figs 24c, d, 25d).

Antenna (Fig. 19i). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 18a). Length 0.6× maximum width. Submarginal arc of setae composed of 10–12 long, simple setae.

Right mandible (Fig. 18b–d). Incisor blade-like with three denticles; kinetodontium with four denticles. Margin between prostheca and mola straight, with minute denticles.

Left mandible (Fig. 18e, f). Incisor blade-like with four denticles; kinetodontium with three denticles. Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 18g). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 18h, i). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one pectinate, spine-like seta and 8–11 short to long, simple setae, not all in a row. Maxillary palp slightly longer than galea-lacinia; palp segment II ca. 1.2× as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Labium (Fig. 18k). Inner margin of glossa with ca. 14 spine-like setae, increasing in length distally; apex with two long and one medium, robust setae; outer margin with approx. nine spine-like setae; Paraglossa with three or four short, simple setae in anteromedial area and one in posterolateral area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I approx. as long as length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with short, broad, rounded, distomedial protuberance; distomedial protuberance 0.2× width of base of segment III; ventral surface with short, fine, simple setae and some short, stout, simple setae; dorsally with 4–6 spine-like setae near outer margin. Segment III about semi-circular, apically rounded; length 0.8× maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 19a–e). Ratio of foreleg segments 1.5:1.0:0.5:0.2. Femur. Slender, length ca. 4× maximum width. Dorsal margin with row of 8–10 medium, curved, spine-like setae and basally 8–10 setae of same type, but standing denser and in more than one row. Further row of short, stout, hook-like setae on distal half of margin. Additionally many short, stout, apically rounded setae along dorsal margin. Same type of setae also on surface and many scattered along ventral margin. Apex rounded, with pair of medium, curved, spine-like setae and many short, hook-like setae. Tibia. Dorsal margin with row of short, stout, apically rounded setae. On surface same type of setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout setae and row of fine, simple setae. Claw with one row of ten denticles.

Terga (Fig. 19f). Surface with irregular rows of U-shaped scale bases and scattered micropores. Posterior margin of tergites: I with triangular, pointed spines or short, triangular, blunt spines; II–IX with triangular, pointed spines, longer than wide. Posterior margin of sternites: I–IV smooth, without spines; V with small, spaced, triangular spines; VI–IX with triangular spines.

Tergalii (Figs 19g, 26c). Tracheae extending from main trunk to inner and outer margins; with light brown band along main trunk of tracheae on anal side. Tergalius I 3/4 as long as segment II, tergalius IV as long as length of segments V and 1/2 VI combined, tergalius VII as long as length of segments VIII and ¼ IX combined.

Paraproct (Fig. 19h). Posterior margin with 18–21 stout spines. Short, stout, apically rounded setae near posterior margin. Surface scattered with scale bases, micropores and fine, simple setae.

Dedicated to Joachim Kaltenbach, the late father of the first author.

Indonesia: Sumatra (Fig. 28b).

The specimens were collected on altitudes between 845 m and 1270 m, in the following physical conditions: slope 5–10%, width of stream 0.2–8 m, depth 7–40 cm, velocity 0.3 m/s–0.8 m/s, pH 6.5–7.5, stream bed dominated by boulder, stones and gravel and only exceptionally by sand and silt. Some of the sites were influenced or polluted by human activities.

Holotype. Indonesia • Sumatra, volcano Talamau, River Pularian; 00°02'15"S, 99°59'24"E; 960 m; 01.IV.2014; leg. M. Gueuning; larva on slide; GBIFCH00592524; MZL. Paratypes. Same data as holotype; larva on slide; GBIFCH00422480; MZL; 18 larvae in alcohol; GBIFCH00406299, GBIFCH00406308, GBIFCH00406398, GBIFCH00406407, GBIFCH00422240, GBIFCH00422245, GBIFCH00422247, GBIFCH00422257, GBIFCH00422262, GBIFCH00422269, GBIFCH00422481, GBIFCH00422527, GBIFCH00422534, GBIFCH00423110, GBIFCH00980904; MZL. Indonesia • West Sumatra, Sawahlunto, Talawi Hilir, Dusun Talimato, UB Farm; 0°35'52"S, 100°43'02"E; 305 m; 25.X.2013; leg. M. Balke; larva on slide; GBIFCH00763628; MZB (temporarily housed in MZL); larva on slide; GBIFCH00592445; MZL; 2 larvae in alcohol; GBIFCH00975608, GBIFCH00980900; MZL.

Larva. Following combination of characters distinguish B. minangkabau sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with small protuberance; segment III slightly pentagonal, apically slightly concave, with projecting point (Fig. 20h); B) dorsal margin of femur with row of long, spine-like setae, denser in basal area (Fig. 21a); C) posterior margin of tergites: I smooth, without spines; II–IV with rounded spines, wider than long, partly fused at base; V–IX with triangular spines, narrower and longer towards last segment (Fig. 21d); posterior margin of sternites: I–VI smooth, without spines; VII and VIII with small, spaced, triangular spines; IX with small, triangular spines; D) paraproct without short, stout, apically rounded setae along posterior margin (Fig. 21f).

Figure 20. 

Branchiobaetis minangkabau sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d left mandible e left prostheca f hypopharynx and superlinguae g maxilla h labium (left: ventral view, right: dorsal view).

Larva (Figs 20, 21, 25a, 26d). Body length 6.5–8.5 mm. Cerci: ca. 2/3 of body length. Paracercus: ca. 1/2 cerci length. Antenna: ca. 2.5× as long as head length.

Figure 21. 

Branchiobaetis minangkabau sp. nov., larva a foreleg b fore femur apex, posterior view c fore claw d tergum IV e tergalius IV f paraproct g base of antenna.

Colouration (Fig. 25a). Head, thorax and abdomen dorsally brown, abdominal segments I and X lighter, abdomen laterally on segments II–IX whitish; head, thorax and abdomen ventrally light brown. Legs with dark brown coxae, femur light brown, apically and dorsally along margin dark brown, with large, medial, dark brown spot; tibia light brown; tarsus basally light brown, dark brown in distal half. Caudalii light brown, primary swimming setae dark brown.

Precursors of turbinate eyes (Fig. 25e) in male last instar larvae representing a pair of egg-shaped maculae; in the middle of this macula, a smaller, round, elevated area with well-expressed facets, ca. eight facets in diameter; peripheral area of the macula with indistinct facets.

Antenna (Fig. 21g). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 20a). Length 0.6× maximum width. Submarginal arc of setae composed of 11–13 long, simple setae.

Right mandible (Fig. 20b, c). Incisor and kinetodontium distally cleft. Incisor blade-like with three denticles; kinetodontium with four denticles. Minute setae outside laterally on first denticle (present on fresh mandibles only). Margin between prostheca and mola straight, with minute denticles.

Left mandible (Fig. 20d, e). Incisor blade-like with three denticles; kinetodontium with three denticles. Minute setae outside laterally on first denticle (present on fresh mandibles only). Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 20f). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, long. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 20g). Galea-lacinia ventrally with one simple, apical seta under canines. Medially with one pectinate, spine-like seta and three or four medium, simple setae. Maxillary palp as long as galea-lacinia; palp segment II 1.1× as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Labium (Fig. 20h). Inner margin of glossa with approx. eight spine-like setae, increasing in length distally; apex with two long and one medium, robust setae; outer margin with two or three spine-like setae; Paraglossa with one simple seta in posterolateral area; dorsally with two long, spine-like setae near inner margin. Labial palp with segment I approx. as long as length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with small, distomedial protuberance; distomedial protuberance 0.3× width of base of segment III; ventral surface with short, fine, simple setae; dorsally with 6–9 spine-like setae near outer margin, not always in a row. Segment III slightly pentagonal, apically slightly concave, with projecting point; length approx. maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 21a–c). Ratio of foreleg segments 1.4:1.0:0.6:0.2. Femur. Length ca. 3× maximum width. Dorsal margin with row of 15–20 long, curved, spine-like setae, basally denser. Many short, stout, apically rounded setae scattered along ventral margin. Apex rounded, with pair of long, spine-like setae and some short, stout setae. Tibia. Dorsal margin with row of short, stout setae. On surface few such setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout setae. Claw with one row of eight or nine denticles.

Terga (Fig. 21d). Surface with irregular rows of U-shaped scale bases. Posterior margin of tergites: I smooth, without spines; II–IV with rounded spines, wider than long, partly fused at base; V–IX with triangular spines, narrower and longer towards last segment. Posterior margin of sternites: I–VI smooth, without spines; VII–VIII with small, spaced, triangular spines; IX with small triangular spines.

Tergalii (Figs 21e, 26d). Tracheae not reaching inner and outer margins; indistinct broad, light brown band along main trunk of tracheae on anal side. Tergalius I as long as 2/3 of segment II, tergalius IV as long as length of segments V and 2/3 VI combined, tergalius VII as long as length of segments VIII and 1/3 IX combined.

Paraproct (Fig. 21f). Posterior margin with 14–24 stout spines. Without short, stout setae near posterior margin. Surface scattered with scale bases, micropores and fine, simple setae.

Dedicated to the indigenous Minangkabau people, who live in the area of Sumatra where the specimens were collected.

Indonesia: Sumatra (Fig. 28b).

The specimens were collected on altitudes of 300 m and 960 m, most of them in a stream with the following physical conditions: slope 25%, width of stream 3–20 m, depth ca. 1.5 m, velocity slow in pool and 0.8 m/s in cascade, pH 8, stream bed dominated by bedrock and stones with patches of sand.

Holotype. Philippines • S. Luzon, Sorsogon, Bulusan, San Roque; 12°44'N, 124°05'E; 290 m; 26. IX. 1996; leg. J. Mendoza; larva on slide; GBIFCH00592344; PNM. Paratypes. Same data as holotype; 1 larva on slide; GBIFCH00763660; MZL. Philippines • Cebu, Cebu City, Cantipla Uno; 10°20'48"N, 123°51'57"E; 100 m; 11. IX. 1996; leg. J. Mendoza; larva on slide; GBIFCH00592341; AdMU; larva in alcohol; GBIFCH00515474; AdMU • Cebu, Cebu City, Bgy. Tabunan, sitio Cantipla 1; 10°24'56"N, 123°49'02"E; 753 m; 16.XII.1998; leg. Panganthion; larva on slide; GBIFCH00654920; MZL; 2 larvae in alcohol; GBIFCH00515475, GBIFCH00980901; AdMU.

Larva. Following combination of characters distinguish B. jhoanae sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with small, rounded protuberance; segment III slightly pentagonal, apically pointed, ca. 0.7× length of segment II, ca. 1.4× as long as width at base, approx. as long as maximal width (Fig. 22h); B) dorsal margin of femur with row of long, spine-like setae (Fig. 23a); C) posterior margin of tergites: I smooth, without spines; II–IX with triangular spines (Fig. 23d); posterior margin of sternites: I–VI smooth, without spines; VII–IX with small, spaced, triangular spines; D) paraproct without short, stout, apically rounded setae along posterior margin (Fig. 23f).

Figure 22. 

Branchiobaetis jhoanae sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d left mandible e left prostheca f hypopharynx and superlinguae g maxilla h labium (left: ventral view, right: dorsal view).

Larva (Figs 22, 23, 25b, 26e). Body length 5.8–7.0 mm. Cerci: ca. ½ of body length. Paracercus: ca. 2/3 of cerci length. Antenna: ca. 2.5× as long as head length.

Figure 23. 

Branchiobaetis jhoanae sp. nov., larva a foreleg b fore femur apex, posterior view c fore claw d tergum IV e tergalius IV f paraproct g base of antenna.

Colouration (Fig. 25b). Head, thorax, and abdomen dorsally brown; head, thorax and abdomen ventrally light brown to brown. Legs light brown to brown, large brown areas along dorsal margin, apex and on medial surface of femur. Caudalii light brown, primary swimming setae dark brown.

Figure 24. 

Habitus, larvae, dorsal view a Branchiobaetis aduncus sp. nov. b Branchiobaetis hamatus sp. nov. c Branchiobaetis joachimi sp. nov. (Sumatra, volcano Sago) d Branchiobaetis joachimi sp. nov. (Sumatra, Bukit Barisan, above Padang).

Antenna (Fig. 23g). Scape distally with short, stout, apically rounded setae.

Labrum (Fig. 22a). Length 0.6× maximum width. Submarginal arc of setae composed of 7–9 long, simple setae.

Right mandible (Fig. 22b, c). Incisor blade-like with three denticles; kinetodontium with four denticles. Margin between prostheca and mola straight, with minute denticles.

Figure 25. 

Habitus, larvae, dorsal view a Branchiobaetis minangkabau sp. nov. b Branchiobaetis jhoanae sp. nov. Precursors of turbinate eyes developing in male last instar larvae c Branchiobaetis hamatus sp. nov. d Branchiobaetis joachimi sp. nov. e Branchiobaetis minangkabau sp. nov.

Left mandible (Fig. 22d, e). Incisor blade-like with four denticles; kinetodontium with three denticles. Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins slightly convex.

Hypopharynx and superlinguae (Fig. 22f). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, long. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Figure 26. 

Larva, tergalii IV a Branchiobaetis aduncus sp. nov. b Branchiobaetis hamatus sp. nov. c Branchiobaetis joachimi sp. nov. d Branchiobaetis minangkabau sp. nov. e Branchiobaetis jhoanae sp. nov.

Maxilla (Fig. 22g). Galea-lacinia ventrally with two simple, apical seta under canines. Medially with one pectinate, spine-like seta and 4–6 medium, simple setae. Maxillary palp approx. as long as galea-lacinia; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Figure 27. 

Distribution maps a Branchiobaetis gen. nov. in Southeast Asia b Known species of Branchiobaetis gen. nov.

Labium (Fig. 22h). Inner margin of glossa with eight or nine spine-like setae, increasing in length distally; apex with two long and one medium, robust, pectinate setae; outer margin with approx. five spine-like setae; Paraglossa with one simple seta in anterolateral area and one simple seta in posterolateral area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I 0.7× as long as length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with small, rounded, distomedial protuberance; distomedial protuberance 0.3× width of base of segment III; ventral surface with short, fine, simple setae; dorsally with five or six spine-like setae near outer margin. Segment III slightly pentagonal, apically pointed; length approx. maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Figure 28. 

Distribution maps a, b new species of Branchiobaetis gen. nov. in Sumatra.

Foreleg (Fig. 23a–c). Ratio of foreleg segments 1.3:1.0:0.6:0.2. Femur. Length ca. 3× maximum width. Dorsal margin with row of 14–21 long, curved, spine-like setae, basally denser. Many short, stout setae scattered along ventral margin. Apex rounded, with pair of long, spine-like setae and some short, stout setae. Tibia. Dorsal margin with row of short, stout setae. On surface few such setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout setae and fine, simple setae. Claw with one row of nine or ten denticles.

Terga (Fig. 23d). Surface with irregular rows of U-shaped scale bases and fine simple setae. Posterior margin of tergites: I smooth, without spines; II–IX with triangular spines. Posterior margin of sternites: I–VI smooth, without spines; VII–IX with small, spaced, triangular spines.

Tergalii (Figs 23e, 26e). Tracheae extending to inner and outer margins; indistinct, broad, light brown band along main trunk of tracheae on anal side. Tergalius I as long as 1/2 of segment II, tergalius IV as long as length of segments V and 1/4 VI combined, tergalius VII as long as length of segments VIII and 1/4 IX combined.

Paraproct (Fig. 23f). Posterior margin with 14–18 stout spines. Without short, stout setae near posterior margin. Surface scattered with scale bases and micropores.

Dedicated to Dr. Jhoana M. Garces (Philippines) for her great contribution to the knowledge of mayflies from the Philippines.

Philippines: Luzon, Cebu (Fig. 29).

Figure 29. 

Distribution map. Branchiobaetis jhoanae sp. nov. in the Philippines.

The specimens were collected on altitudes between 100 m and 750 m, on Cebu in stream runs on bottom gravel or rock surface.