Branchiobaetis gen. nov.

Figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29

Type species.

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

Species included in Branchiobaetis gen. nov.

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.

Diagnosis.

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.

Etymology.

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.

Description.

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.

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.

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.

Distribution

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