Labiobaetis dayakorum, Kaltenbach & Gattolliat, 2020

Kaltenbach, Thomas & Gattolliat, Jean-Luc, 2020, Labiobaetis Novikova & Kluge in Borneo (Ephemeroptera, Baetidae), ZooKeys 914, pp. 43-79 : 43

Labiobaetis dayakorum sp. nov. Figures 5 , 6 , 11a , 15c

Diagnosis.

Larva. Following combination of characters: A) dorsal surface of labrum with submarginal arc of 10-12 long, feathered setae; B) labial palp segment II with a large, lobed distomedial protuberance, segment III slightly pentagonal; C) fore femur rather broad, length ca. 4 × maximum width, dorsal margin with a row of 12-14 curved, spine-like setae; D) hindwing pads well developed; E) paraproct distally not expanded, with 30-37 marginal, stout spines.

Description.

Larva (Figs 5 , 6 , 11a ). Body length 5.2 mm; antenna: approximately 2.5 × as long as head length; cerci broken.

Colouration. Head, thorax and abdomen dorsally brown; head and thorax with bright median, dorsal suture, abdominal segment X light brown. Head, thorax and abdomen ventrally light brown, legs light brown with a brown spot medially and apically on femur, caudal filaments light brown.

Antenna (Fig. 6g ) with scape and pedicel subcylindrical, with well-developed distolateral process at scape.

Labrum (Fig. 5a ). Rectangular, length 0.7 × maximum width. Distal margin with medial emargination and a small process. Dorsally with medium to long, fine, simple setae scattered over surface; submarginal arc of setae composed of 10-12 long, feathered setae. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae; ventral surface with five short, spine-like setae near lateral and anterolateral margin.

Right mandible (Fig. 5b, c ). Incisors fused. Outer and inner sets of denticles with 4 + 3 denticles and one minute intermediate denticle. Inner margin of innermost denticle with a row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, with minute denticles. Tuft of setae at apex of mola present.

Left mandible (Fig. 5d, e ). Incisors fused. Outer and inner sets of denticles with 4 + 3 denticles and one minute intermediate denticle. Prostheca robust, apically with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with minute denticles towards subtriangular process. Subtriangular process long and slender, above level of area between prostheca and mola. Denticles of mola apically constricted. Tuft of setae at apex of mola present.

Both mandibles with lateral margins almost straight. Basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx (Fig. 5f ). Lingua approx. as long as superlingua. Lingua longer than broad; medial tuft of stout setae poorly developed; distal half laterally expanded. Superlingua rounded; lateral margin rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 5g ). Galea-lacinia with two simple, robust apical seta under crown. Inner dorsal row of setae with three denti-setae, distal denti-seta tooth-like, middle and proximal denti-setae slender, bifid and pectinate. Medially with one bipectinate, spine-like seta and four medium, simple setae. Maxillary palp 1.2 × as long as length of galea-lacinia; 2-segmented; palp segment II 1.6 × length of segment I; setae on maxillary palp fine and simple, scattered over surface of segments I and II; apex of last segment rounded, with excavation at inner distolateral margin.

Labium (Fig. 5h, i ). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with seven or eight spine-like setae increasing in length distally; apex with two long and one medium, robust, pectinate setae; outer margin with five or six long, spine-like setae; ventral surface with short, fine, simple, scattered setae. Paraglossa sub-rectangular, curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and two medium, simple setae in anteromedial area; dorsally with a row of three long, spine-like setae near inner margin. Labial palp with segment I 0.9 × length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with large, lobed distomedial protuberance; distomedial protuberance 0.7 × width of base of segment III; inner and outer margin with short, fine, simple setae; dorsally with two medium, spine-like, simple setae near outer margin. Segment III slightly pentagonal; apex truncate; length 1.1 × width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hindwing pads (Fig. 6h ) well developed.

Foreleg (Fig. 6a, b ). Ratio of foreleg segments 1.1:1.0:0.4:0.2. Femur. Length ca. 4 × maximum width. Dorsal margin with a row of 12-14 curved, spine-like setae; length of setae 0.26 × maximum width of femur. Apex rounded, with one pair of curved, spine-like setae and some short, stout setae. Many short, stout, lanceolate setae scattered along the ventral margin; femoral patch absent. Tibia. Dorsal margin with a row of short, stout setae, on apex one longer seta, and a row of short, stout setae close to dorsal margin. Ventral margin with a row of curved, spine-like setae, on apex two spine-like seta and a tuft of long, fine, simple setae. Anterior surface scattered with stout, lanceolate setae. Patellotibial suture present on basal 1/3 area. Tarsus. Dorsal margin with a row of short, stout setae. Ventral margin with a row of curved, spine-like setae. Tarsal claw with one row of 9-13 denticles; distally pointed; with four stripes; subapical setae absent.

Terga (Fig. 6c, d ). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergum IV with rounded or triangular spines, wider than long.

Gills (Fig. 6e ). Present on segments I - VII. Margin with small denticles intercalating fine simple setae. Tracheae extending from main trunk to inner and outer margins. Gill I as long as length of ½ segment II. Gill IV as long as length of segments V and 1/3 VI combined. Gill VII as long as length of segments VIII and 1/3 IX combined.

Paraproct (Fig. 6f ). Distally not expanded with 30-37 stout marginal spines. Surface scattered with U-shaped scale bases, fine, simple setae and micropores. Cercotractor with medium marginal spines.

Etymology.

Dedicated to the indigenous Dayak people of Borneo.

Distribution.

Indonesia: Kalimantan (Fig. 15c ).

Biological aspects.

The specimens were collected at an altitude of 200 m, partly in a large river.

Type-material.

Holotype. Larva (on slide, GBIFCH 00592281), Indonesia, East Kalimantan, Bas. Malinau, River Seturan, loc. Seturan, tributary, 03°00.08'N, 116°30.80'E, 28.III.2001, P. Derleth and B. Feldmeyer leg. Paratypes. 1 larva (on slide, GBIFCH 00592255), Indonesia, East Kalimantan, Bas. Malinau, River Rian, loc. Seturan (1998-block 32-33), tributary, 03°00.95'N, 116°32.27'E, 30.III.2001, P. Derleth leg.; 1 larva (on slide, GBIFCH 00592256), Indonesia, East Kalimantan, Bas. Malinau, River Seturan, loc. Seturan (2001-block 57), trib. Benganau, 02°59.37'N, 116°30.77'E, 11.IV.2001, P. Derleth and B. Feldmeyer leg. All material deposited in MZL.

Figures

Figure 5. Labiobaetis dayakorum sp. nov., larva morphology: a Labrum b Right mandible c Right prostheca d Left mandible e Left prostheca f Hypopharynx g Maxilla h Labium i Apex of paraglossa.

Figure 6. Labiobaetis dayakorum sp. nov., larva morphology: a Foreleg b Fore claw c, d Tergum IV e Gill IV f Paraproct g Antennal scape h Metanotum.

Figure 11. Habitus, larvae, dorsal view: a Labiobaetis dayakorum sp. nov. b Labiobaetis paraoperosus c Labiobaetis moriharai.

Figure 15. Distribution of Labiobaetis in Borneo: a Labiobaetis moriharai b Labiobaetis borneoensis c Labiobaetis bakerae sp. nov. and Labiobaetis dayakorum sp. nov. d Labiobaetis penan sp. nov. T: type locality.