Labiobaetis rimba, Kaltenbach, Thomas & Gattolliat, Jean-Luc, 2019

Kaltenbach, Thomas & Gattolliat, Jean-Luc, 2019, The tremendous diversity of Labiobaetis Novikova & Kluge in Indonesia (Ephemeroptera, Baetidae), ZooKeys 895, pp. 1-117 : 1

14. Labiobaetis rimba sp. nov.

Diagnosis.

Larva. Following combination of characters: A) dorsal surface of labrum with submarginal arc of 20 clavate setae; B) labial palp segment II with an elongated, thumb-like distomedial protuberance, segment III slightly pentagonal, apically with a small projection; C) left mandible without setae at apex of mola; D) maxillary palp much longer than galea-lacinia, apically rounded and curved inward, with excavation at inner distolateral margin; E) fore femur rather slender, length ca. 4 × maximum width, dorsal margin with a row of 10-13 curved, spine-like setae; F) paraproct distally not expanded, with ca. 32 stout marginal spines.

Description.

Larva ( Figs 24 , 25 , 49b ). Body length 4.2 mm.

Colouration. Head and thorax dorsally brown, with bright median, dorsal suture, thorax with pattern as in Fig. 49b , forewing pads with dark striation. Abdomen dorsally reddish-brown. Head, thorax, and abdomen ventrally light brown, legs transparent with brown spots distomedially on femur, caudal filaments light brown.

Antenna with scape and pedicel subcylindrical, without distolateral process at scape; flagellum with broad, lanceolate spines and fine, simple setae on apex of each segment.

Labrum ( Fig. 24a, b ). Rectangular, length 0.6 × maximum width. Distal margin with medial emargination and a small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of setae composed of 20 long, clavate 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. 24c, d ). 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 straight. Tuft of setae at apex of mola present.

Left mandible ( Fig. 24e, f ). 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 absent.

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

Hypopharynx ( Fig. 24g ). Lingua longer than superlingua. Lingua longer than broad; medial tuft of stout setae well developed; distal half laterally expanded. Superlingua straight; lateral margin rounded; fine, long, simple setae along distal margin.

Maxilla ( Fig. 24h, i ). Galea-lacinia with two simple, robust apical setae 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 3-4 medium, simple setae. Maxillary palp 1.5 × as long as length of galea-lacinia; two segmented; palp segment II 1.4 × length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment rounded and curved inward, with excavation at inner distolateral margin.

Labium ( Fig. 24j ). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with six spine-like setae increasing in length distally; apex with two long and one medium, robust, pectinate setae; outer margin with 4 long, spine-like setae; ventral surface with short, fine, simple setae. Paraglossa sub-rectangular, curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and 4-5 medium, simple setae in anteromedial area; dorsally with a row of four 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 elongated, thumb-like distomedial protuberance; distomedial protuberance 0.8 × width of base of segment III; inner and outer margin with short, fine, simple setae; dorsally with two long, spine-like, simple setae near outer margin. Segment III slightly pentagonal; apex with small projection; length 1.0 × width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg ( Fig. 25a, b, c, d ). Ratio of foreleg segments 1.2:1.0:0.4:0.1. Femur. Length ca. 4 × maximum width. Dorsal margin with a row of 10-13 curved, spine-like, apically rounded setae; length of setae 0.22 × maximum width of femur. Apex rounded; with one pair of curved, spine-like setae, some short stout setae and some fine, simple setae. Short to medium stout, lanceolate setae scattered along the ventral margin; femoral patch reduced to a few setae. Tibia. Dorsal margin with a row of minute, stout setae and fine, simple setae. Ventral margin with a row of curved, spine-like setae, on apex some stout, spine-like and partly bipectinate setae and a tuft of fine, simple setae. Anterior surface scattered with stout, lanceolate setae. Patellotibial suture present on basal 1/3. Tarsus. Dorsal margin with a row of fine, simple setae. Ventral margin with a row of curved, spine-like, bipectinate setae (pectination difficult to see). Tarsal claw with one row of 9-10 denticles; distally pointed; with two stripes; subapical setae absent.

Tergum ( Fig. 25e ). Surface with rows of U-shaped scale bases and scattered micropores. Posterior margin of tergum IV with triangular spines, wider than long.

Gills ( Fig. 25f ). Present on segments II–VII. Margin with small denticles intercalating fine simple setae. Tracheae extending from main trunk to inner and outer margins. Gill IV as long as length of segments V and 1/2 VI combined. Gill VII as long as length of segments VIII and 1/4 IX combined.

Paraproct ( Fig. 25g ). Distally not expanded, with ca. 32 stout marginal spines. Surface scattered with U-shaped scale bases. Cercotractor with numerous small marginal spines.

Etymology.

Dedicated to the indigenous Rimba people from Sumatra.

Distribution.

Indonesia: Sumatra.

Biological aspects.

The specimens were collected at altitudes of 75 m and 275 m.

Type-material.

Holotype. Larva (on slide, GBIFCH 00592222), Indonesia, Sumatra Barat, Barung-Barung, 01°06.03'S, 100°29.12'E, 75 m, 24.V.2010, J.-M. Elouard leg. Temporary deposited in MZL before definitely housed in MZB. Paratypes. 2 larvae (1 on slide, GBIFCH 00592223, 1 in alcohol, GBIFCH 00515366, deposited in MZL), same data as holotype; 1 larva (on slide, GBIFCH 00592224, deposited in MZL), Indonesia, Sumatra Barat, Sawahlunto, stream, 275 m, 10.XI.2011, 00°41.33'S, 100°46.72'E, M. Balke leg. (UN5).

Figures

Figure 24. Labiobaetis rimba sp. nov., larva morphology: a Labrum b Seta of the submarginal arc on the dorsal surface of the labrum c Right mandible d Right prostheca e Left mandible f Left prostheca g Hypopharynx h Maxilla i Maxillary palp segment II h Labium.

Figure 25. Labiobaetis rimba sp. nov., larva morphology: a Foreleg b Fore femur dorsal seta c Fore tarsus ventral seta d Fore claw e Tergum IV f Gill IV g Paraproct h Scape.

Figure 49. Habitus, larvae, dorsal view: a Labiobaetis paradiffundus sp. nov. b Labiobaetis rimba sp. nov., without head c Labiobaetis gueuningi sp. nov. d Labiobaetis minang sp. nov., after DNA extraction.