Baetis (Tenuibaetis) octomaculatus, Kluge & Srinivasan & Sivaruban & Barathy & Isack, 2023

Kluge, Nikita, Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2023, Contribution to the knowledge of the subgenus Tenuibaetis Kang & Yang 1994 (Ephemeroptera, Baetidae, Baetis s. l.), Zootaxa 5277 (2), pp. 201-258 : 249-251

8. Baetis (Tenuibaetis) octomaculatus sp. n.

( Figs 15–19 , 242–278 )

Etymology. Allusion to eight contrasting dark brown maculae on abdominal terga in all stages of both sexes ( Figs 248 , 266, 267, 270, 271 ).

Material examined. Holotype: L-S-I ♀ {specimen [XVIII](2) 2015}, THAILAND, Pai , river Moei, 14.II.2015, coll. N. Kluge & L. Sheiko. Paratypes: the same place, date and collectors: 2 L-S-I ♀, 1 S♁, 30 larvae; river Pai , 11.I.1998, coll. Grigorenko: 1 L/S ♁; Mae-Sae , 15–19. II.2015, coll. N. Kluge & L. Sheiko: 2 larvae ; Erawan National Park , 2–4. II.2015, coll. N. Kluge & L. Sheiko: 1 S-I♁, 1 S-I ♀ , 9 I♁, 2 larvae.

Descriptions

Larva. CUTICULAR COLORATION: Head brown ( Figs 243, 246 ). Pronotum brown, with sigilla slightly darker than background; mesonotum and fore protoptera brown, with diffusive blanks ( Fig. 242, 245 ). Thoracic pleura brownish, sterna colorless. Legs with darker and lighter brown areas; fore femur with wide oval proximal blank ( Figs 253–255 ). Abdominal terga vary from nearly uniformly brown to more or less contrasting; tergum IV either nearly as dark as others ( Fig. 247 ), or colorless laterally ( Fig. 244 ). Caudalii uniformly brown.

HYPODERMAL COLORATION: In young and mature larvae of both sexes, abdominal terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Fig. 248 ).

SHAPE AND SETATION: Labrum of medium proportions ( Fig. 249 ). Mandibles— Figs 250–251 . Maxilla and labium— Fig. 252 .

Hind protoptera present ( Figs 17–19 ).

Stout two-channel setae forming row along outer side of femur (including two subapical setae) elongate, blunt, distally widened and flattened ( Figs 253–255 ). Anterior-apical margin of femur with small, pseudo-bifurcate setae, as on tibiae ( Fig. 257 ). Stout setae on anterior side of femur mostly elongate, distally widened and rounded, varying from large to small ( Figs 253–255 , 257–258 ).

Tibia of each leg with pseudo-bifurcate setae on outer side, smaller and sparser on fore leg ( Fig. 259 ), larger and denser on middle and hind legs ( Fig. 260 ). Stout setae along patella-tibial suture two-channel, short, distally widened and rounded ( Figs 259–260 ).

Denticles on posterior margins of all abdominal terga I–X well-developed, short and blunt ( Figs 261–263 ). Denticles on posterior margin of sternum triangular, present on sternum IX ( Fig. 264 ), fewer on sternum VIII; in male row of denticles not interrupted by protogonostyli. Paraproct with pointed denticles ( Fig. 264 ). Tergalius I much smaller than others ( Figs 244, 247 ). Paracercus significantly smaller than cerci ( Fig. 247 ).

Subimago. CUTICULAR COLORATION: Head colorless, antennae brown. Pronotum with light brown and colorless areas. Mesonotum mostly light brownish ( Fig. 265 ). Thoracic pleura and sterna with light brownish and dark brown areas (as in Fig. 215 ). Legs brownish ( Fig. 274 ). Abdominal terga and sterna light brownish.

HYPODERMAL COLORATION: In both sexes, abdominal terga mostly ochre; terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Fig. 271 ).

Imago, male ( Figs 266, 272 ). Head light brown. Antennae light brown. Turbinate eyes with facetted surface orange, stem ochre. Thorax brown. Forewing with membrane entirely colorless; veins ochre or brown; pterostigma with few oblique cross veins and disconnected vein fragments. Hind wing diminished, colorless, with short and non-hooked costal projection, with 2 longitudinal veins ( Figs 15–16 ). Legs either uniformly ochre ( Fig. 273 ), or with diffusive reddish markings. Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments). Abdominal terga II – III and VI – VII with pair of contrasting dark brown maculae and brownish-ochre area between them; these and other abdominal terga with dark brown line on posterior margin; terga IV – V mostly light ochre, tergum VIII mostly brownish-ochre, terga IX –X lighter ochre ( Figs 266, 272 . Cerci ochre. Gonostyli ochre; 1st segment slightly narrowing toward apex; 3rd (terminal) segment short, often truncate ( Fig. 277 ), sometimes clavate ( Fig. 276 ). Gonovectes sharply bent, light brownish. Sterno-styligeral muscle vestigial ( Fig. 277 ).

Imago, female ( Figs 267, 270 ). Head ochre. Thorax ochre. Hind wing much smaller than in male ( Fig. 18 ). All tarsi with 2 apical spines (fore tarsus on 2nd and 3rd segments, middle and hind tarsi on 1st+2nd and 3rd segments). Abdominal terga mostly ochre; terga II – III and VI – VII with pair of contrasting dark brown maculae; these and other abdominal terga with dark brown line on posterior margin ( Figs 267, 270 ).

Dimension. Forewing length 4 mm.

Distribution. Thailand.

Comparison. The new species differs from other known species by peculiar hypodermal coloration which is well-expressed in all stages of the both sexes, i.e. with eight dark brown maculae, by a pair on the abdominal terga II, III, VI and VII. By greatly diminished hind wings of female, the new species resembles B. (T.) parvipterus ; it differs from B. (T.) parvipterus , besides the hypodermal coloration, by very long stout setae on anterior surface of femur.

Figures

FIGURES 13–21. Imaginal hind wings and larval protoptera (under the same magnification). 13–14, female Baetis (Tenuibaetis) frequentus from India; 15–17, male B. (T.) octomaculatus sp. n.; 18–19, female of same species; 20–21, male B. (T.) bialatus sp. n. (13, 15, 20, metathorax of imago with hind wing; 14, 21, larval exuviae of metanotum; 16, 18, hind wing of imago; 17, 19, cuticle from metathorax of larva ready to molt to subimago, with subimaginal wing inside protopteron: crumpled on Fig. 17, non-crumpled on Fig. 19).

FIGURES 242–248. Baetis (Tenuibaetis) octomaculatus sp. n. 242–247, exuviae of female larvae: 242, 245, half of pronotum and mesonotum; 243, 246, head; 244, 247, abdomen; 248, young larva to show hypodermal coloration (242–244, holotype).

FIGURES 249–252. Baetis (Tenuibaetis) octomaculatus sp. n. 249, labrum (holotype); 250–251, left and right mandibles; 252, maxilla and labium.

FIGURES 253–256. Baetis (Tenuibaetis) octomaculatus sp. n. (holotype). 253–255, larval exuviae of fore, middle and hind legs; 256, base of femur with villopore.

FIGURES 257–264. Baetis (Tenuibaetis) octomaculatus sp. n. 257–258, fore and hind femora; 259–260, fore and middle tibiae; 261–263, abdominal terga I, VII and X; 264, abdominal sternum IX and paraprocts (257–260, holotype).

FIGURES 265–274. Baetis (Tenuibaetis) octomaculatus sp. n. 265, subimaginal exuviae of half of mesonotum; 266, male imago; 267, female imago; 268–269, fore legs of two female imagines (268, holotype); 270, female imago; 271, male subimago; 272, abdomen of male imago; 273, fore leg of male imago; 274, its subimaginal exuviae.

FIGURES 275–278. Baetis (Tenuibaetis) octomaculatus sp. n. 275, subimaginal gonostyli crumpled under larval cuticle; 276, imaginal genitalia; 277, imaginal genitalia of another individual, with focus on ventral side; 278, the same, with focus on gonovectes. Abbreviation: s.s, sterno-styligeral muscle.

FIGURES 215–224. Baetis (Tenuibaetis) bialatus sp. n. 215, subimaginal exuviae of mesopleuron; 216, subimaginal exuviae of half of mesonotum; 217–218, exuviae of fore and hind legs of male subimago; 219–220, fore and middle legs of male imago; 221, male imago; 222, female imago; 223, subimaginal exuviae of abdominal segments VIII–IX; 224, egg (215–220, holotype).