Indobaetis costai Müller-Liebenau & Morihara 1982

Kluge, Nikita J. & Novikova, Eugenia A., 2014, Systematics of Indobaetis Müller-Liebenau & Morihara 1982, and related implications for some other Baetidae genera (Ephemeroptera), Zootaxa 3835 (2), pp. 209-236 : 215-219

Indobaetis costai Müller-Liebenau & Morihara 1982

( Figs 2, 3 , 5–35 , 38, 39 , 41–44 )

Material. SRI LANKA: Uva province., Badulla district, Haputale 15–23.I.2011, coll. N. Kluge & L. Sheyko: 5 L- S-I♂, 1 L-S/I♂, 1 L-S♂, 7 L-S-I♀, 1 L-S/I♀, 2 L-S♀, S-I♀, 34 larvae; the same district, Lemastota Oya, 20–21.I.2011, coll. N. Kluge & L. Sheyko: 27 larvae; Sabaragamuwa province, river Seetha Sangula, Dalhausie near Sri Pada (Adam's Peak), 24–26.I.2011, coll. N. Kluge & L. Sheyko: 10 larvae; Central province, Nuwara Eliya district, Ginigathhena (17 km N Hatton), 31.I–3.II.2011, coll. N. Kluge & L. Sheyko: 1 larva.

Descriptions.

Larva. CUTICULAR COLORATION: Dorsum of head, thorax and abdomen nearly uniformly light brown, with diffusive lighter areas; medioposterior sigilla either lighter than background ( Müller-Liebenau & Morihara 1982: Fig. 3 ), or of the same color. Thoracic and abdominal sterna colorless. Legs nearly uniformly light, femora can be slightly diffusively darkened on inner and outer sides. Caudalii nearly uniformly light brownish, proximally darker and distally lighter.

HYPODERMAL COLORATION: Either not expressed, or posterior margin of each abdominal tergum bordered by darker brown, as in imago ( Fig. 20 ).

SHAPE AND SETATION: Head moderately narrowed; frons between antennae bases elevated, but flat; arms of frontal suture angulated ( Figs 41, 44 ). 2nd segment of labial palp, being unusually narrowed, retains muscle which moves 3rd segment. Pronotum with length less than ½ width ( Fig. 43 ). Patella-tibial suture developed on all legs ( Fig. 22 ). Tergalii unable for rhythmic respiratory movements. Caudalii with well-developed primary swimming setae on lateral sides of paracercus and median sides of cerci. Other characters as described by Müller- Liebenau & Morihara (1982).

MALE GENITALS. Subimaginal gonostyli developing under cuticle of mature male larva, are bent mediallycranially, so that 1st and 2nd segments are directed medially, and 3rd segment is directed medially-cranially ( Figs 28, 29 ).

Subimago. CUTICULAR COLORATION: Pronotum light brow with colorless blanks. Mesonotum light brown, with medioparapsidal suture, sublateroscutum and lateral area of scutellum contrastingly colorless ( Fig. 18 ). Thoracic sterna and pleura with light membranes and brown sclerites; posterior part of postsubalar sclerite with sharply convex dorsal margin ( Fig. 19 ). Wings gray. Cuticle of legs nearly uniformly light brownish. Cuticle of abdominal terga and sterna uniformly light grayish-brown, with small lighter medio-anterior and medioposterior sigilla.

HYPODERMAL COLORATION: Similar to imago (see below).

TEXTURE: On fore leg of male subimago, 1st tarsomere covered with pointed microlepides; 2nd–4th tarsomeres covered with blunt microlepides, with pointed microlepides near distal margin; 5th tarsomere covered with pointed microlepides ( Figs 6–8 ). On middle and hind legs of both sexes 1st+2nd, 3rd and 4th tarsomeres covered with blunt microlepides, with pointed microlepides near distal margin; 5th tarsomere covered with pointed microlepides ( Figs 11–17 ). Fore leg of female (4-segmented—see below) with the same texture as on middle and hind legs ( Figs 2 , 5 ).

Imago, male. Head light brown with ocher. Turbinate eyes high, nearly cylindrical, slightly widened apically, uniformly red ( Fig. 25 ). Thorax light brown with ocher membranes, dorsally slightly darker brown. Wing with basal sclerite and very bases of longitudinal veins light brownish; remainder parts of veins, including costal brace, pale or colorless; wing membrane colorless. Cross veins flattened and widened, but not colored ( Fig. 23 ). Pterostigma with few oblique veins, which can be either anastomozed ( Fig. 23 ), or simple. Hind wings absent. Fore legs uniformly light ocher; middle and hind legs lighter. On fore leg tibia 2 times longer than femur, tarsus 2 times shorter than tibia (i.e. subequal to femur). On middle and hind legs tibia 1.25 times longer than femur, tarsus 3 times shorter than tibia. Abdominal segment I light brownish; segments II–VI whitish, but not translucent; segments VII–X ocher with brownish; each tergum I–X with brown band on posterior margin ( Fig. 20 ). Genitals light brownish. Cerci uniformly light ocher.

GENITAL STRUCTURE ( Figs 21 , 24 ): Unpaired sterno-styligeral muscle present. Gonovectes weak and slightly bent. Unistyligers with convexities on median sides. Gonostylus with 1st segment conic and not separated from 2nd segment; 3rd segment narrow and elongate.

Imago, female. Head light brown with ocher, flattened, short and wide, with eyes small and widely separated ( Fig. 26 ). Thorax light brown with ocher. Legs uniformly light ocher. Wing with longitudinal and cross veins brown, membrane slightly colored with pale ocher. Fore leg has the same structure as middle and hind leg, with tarsus 4-segmented ( Fig. 3 ). Abdominal terga either nearly uniformly ocher-brown, or each tergum ocher in middle part and brown in anterior, posterior and lateral parts. Abdominal sterna ocher.

Egg ( Figs 30–35 ). About 0.1 mm length, subcylindrical. Chorion thin, armed with stick-like ridges which are connected by their ends and form irregular net with large cells; in middle of each cell locates a shallow round protuberance surrounded by smaller protuberances; other surface of cell covered by irregular protuberances. Micropile small, round, often locates at point where several ridges are connected.

Dimension. Fore wing length 4.5–5 mm.

Distribution and habitat. Sri Lanka. Larvae are common in various mountain streams with stony bottom.

Figures

FIGURES 1 – 4. Fore tarsus of female. 1, female subimago of Nigrobaetis (Takobia) muticus; 2, female subimago of Indobaetis costai; 3, imago of the same specimen; 4, female subimaginal tarsus of Indobaetis microfolius sp. n. visible through larval cuticle. Abbreviations: t 1 – t 5, tarsomeres 1 – 5; t 1 & 2, fused first and second tarsomeres.

FIGURES 5 – 10. Indobaetis costai. 5, fore tarsus of female subimago; 6 – 8, fore tarsus of male subimago and its enlarged base; 9, scales on abdominal tergum; 10, apex of left maxilla, dorsal view. Abbreviations: ds 1 and ds 2, first and second dentisetae.

FIGURES 11 – 17. Indobaetis costai, middle leg of subimago and its details. Abbreviations: bml, blunt microlepides; mt, microtrichiae; pml, pointed microlepides; t 1 & 2, fused first and second tarsomeres; t 3 – t 5, tarsomeres 3 – 5.

FIGURES 18 – 22. Indobaetis costai. 18, subimaginal exuviae of left half of mesonotum; 19, subimaginal exuviae of left subalar sclerite, postsubalar sclerite and lateropostnotal crest; 20, abdominal segments I – VI of male imago, spread on slide; 21, genitals of male imago (intersegmental ventral muscles taken away and unpaired sterno-styligeral muscle visible though integument); 22, part of larval fore leg.

FIGURES 23 – 29. Indobaetis costai. 23 – 25, male imago: 23, wing; 24, genitals (ventral view, muscles of middle and left parts shown by interrupted lines); 25, head and dorsal outline of pronotum and anteronotal protuberance, lateral view. 26, head of female imago, dorsal view. 27, subimaginal exuviae of right unistyliger and gonostylus; 28, subimaginal genitals developing under larval cuticle; 29, the same at earlier phase. Abbreviations: gs 1 – gs 3, 1 st – 3 rd segments of gonostylus; m. s, median sternostyligeral muscle; m. IX – X, intersegmental ventral muscles going from base of 9 th abdominal segment to base of 10 th abdominal segment; us, unistyliger.

FIGURES 30 – 35. Indobaetis costai, eggs and their enlarged micropilar areas.

FIGURES 36 – 39. Posterior view on 10 th abdominal segment (cerci and paracercus taken away). 36, Nigrobaetis (Takobia) maxillaris; 37, undescribed species of Papuanatula from Baliem Valley (Papua province of Indonesia); 38, 39, two specimens of Indobaetis costai.

FIGURES 40 – 45. Indobaetis spp., larvae. 40, I. starmuehlneri, head; 41 – 44, I. costai: 41, head; 42, claw of left leg, ventral view; 43, exuviae of right half of pronotum and mesonotum; 44, exuviae of frons. 45, I. microfolius sp. n., the same.