Platybaetis nayokensis, Sutthinun & Gattolliat & Boonsoong, 2018

Sutthinun, Chanaporn, Gattolliat, Jean-Luc & Boonsoong, Boonsatien, 2018, A new species of Platybaetis Müller-Liebenau, 1980 (Ephemeroptera: Baetidae) from Thailand, with description of the imago of Platybaetis bishopi Müller-Liebenau, 1980, Zootaxa 4378 (1), pp. 85-97 : 89-92

Platybaetis nayokensis sp. nov.

( Figs. 3–4 , 13–14 , 16 , 18 , Fig. 20 , 21–25 , 27–32 , 35–36 )

Material examined: HOLOTYPE: male I (reared from larva, L-SI-I), THAILAND, Nakhon Nayok headwater stream, Wang Takrai, Mueang Nakhon Nayok district , Nakhon Nayok province, 14° 19’ 35” N 101° 18’ 23” E, alt. 30 m, 9-XII-2014, C. Sutthinun leg. ( ZMKU) . PARATYPES: female I (reared from larva, L-SI-I), same data as holotype ( ZMKU); 7 L and 2 last instar L on microscopic slides , same data as holotype ( ZMKU); 2 mature L (GBIFCH00238457), 1 L on slide (GBIFCH00585171) , same data as holotype ( MZL); 9L, 1 female SI (reared, L- SI), 23-XII-2014 , same locality as holotype ( ZMKU); 10 larvae , 4 female SI (reared, L-SI), 4 male SI (reared, L- SI), 15-II-2017, same locality as holotype ( ZMKU) ; 6 larvae, 1 female SI (reared, L-SI), 3 male SI (reared, L-SI), 25-II-2017, same locality as holotype ( ZMKU).

Descriptions. Larva. ( Figs 3–4 , 21–25 , 27–32 )

Length: Body 6.5–7.2 mm. Cerci 6.0– 6.8 mm, terminal filament 0.16–0.17 mm, antennae 0.80-0.96 mm.

Head. Greyish brown with irregular, poorly visible, darker marking on verteX and frons with 3 black ocelli. Antennae ecru. Turbinate eyes black. Hind margin of head in male and female larvae with no incision.

Labrum ( Figs. 21–22 ) trapezoid; distal margin with row of apically bifid setae, dorsal surface with one pair of medium setae and arc of 7 stout short setae.

HypopharynX ( Fig. 27 ) with minute thin setae, lingua trilobate.

Left mandible ( Fig. 28 ) incisors with 6 denticles; without setae basally.

Right mandible ( Fig. 29 ) incisors with 6 denticles; tuft of setae reduced at the apeX of the mola. Size of the teeth of the mandibles similar to P. bishopi ,.

MaXillae ( Fig. 30 ) with distal dentiseta stout, similar to 3 canines; setae of inner-dorsal row twice longer than setae of inner-ventral row. Palps 2-segmented; second segment slightly longer than first, inner margin straight, outer margin slightly falcate; covered with abundant small thin setae.

Labium ( Figs. 23, 24 , 31 ) with glossae slightly longer than paraglossae; glossa with 2 minute, blunt setae at apeX; one large pointed peculiar seta near apeX ( Fig. 24 ); a few small setae on dorsal margin; apeX of paraglossa with 3 rows of stout setae; palps 3-segmented, segment III globular with numerous short stout acute setae.

ThoraX. Colouration pale greyish brown. Pronotum nearly as broad as head capsule. Hindwing pads absent. Proportions of fore legs: tibia 1.5 of femur length; tarsus 2.2 times shorter than tibia. Middle and hind legs: tibia 1.3-1.4 of femur length; tarsus 2.5 times shorter than tibia. Femora dorsally with a row of long marginal setae and with conical submarginal setae. Tibiae with regular row of long setae and with a row of minute blunt setae dorsally; apeX with one medium seta seta dorsally. Tarsi with one ventral row of short setae ending with one long fine bristle near apeX; one dorsal row of long setae; claws ( Fig. 25 ) with a single row of 9–12 denticles increasing in size towards apeX, longest denticle near apeX.

Abdomen. Colouration greyish brown ( Figs. 3, 4 ); terga V, VIII and IX generally slightly lighter; terga II–IX each with dark grey medioanterior and medioposterior sigilla; medioanterior sigilla oval and divergent posteriorly, medioposterior sigilla round.

Terga ( Fig. 32 ) posterior margins with acute denticles 1.5 longer than broad.

Gills ( Figs. 3, 4 ) on segments I–VII, simple, leaf-like and rather broad; with dark tracheation; without setae.

Paraproct similar to Fig. 2d in Müller-Liebenau (1980a), eXpanded, surface with numerous scale and setal bases.

Cerci shorter than the body; paracercus reduced to 1 segment.

Male imago ( Fig. 13 , 18, 20 )

Measurement. Body 6.2 mm; forewing 7.2 mm.

Head. Whitish. Antenna with scape and pedicel medium to dark brown, flagellum medium brown to ecru. Facetted surface of turbinate eyes light orange, lateral face light yellow apically ( Fig. 13 ).

ThoraX. Light brown, with a few diffusive yellowish maculae on pleura laterally and a few diffusive blackish maculae closed lateroparapsidal suture ( Fig. 13 ). Pronotum with a pair of black marks. Anteronotal protuberance flattened and not prominent. All legs pale whitish eXcept femora with large, diffusive, brownish macula. Tarsus of middle and hind legs with 2 apical spines (on 1st+2nd and on 3rd tarsomeres). Foreleg femora with large, diffusive, brownish macula; middle and hind legs femora with small oval brownish macula; tarsi blackish. Proportions of forelegs: tibia 1.8 of femur length; tarsus shorter than tibia. Proportions of middle and hind legs: tibia 1.3–1.4 of femur length; tarsus 2.7–3.0 times shorter than tibia. Forewing ( Fig. 16 ) with a dark brown and orange base longitudinal veins colorless eXtensively bordered with dark brown in proXimal fourth; other parts of membrane colorless; cross-veins colorless. Pterostigma with 4 oblique cross-veins; two intercalaries in every space between main veins shorter than distance between surrounding veins.

Abdomen. Abdominal terga ( Fig. 18 ) and sterna translucent, eXcept terga VIII–X white. Terga III–VII with a pair of orange-brown stripes on each side; terga VIII and IX with a pair of brownish maculae medially. Cerci colourless.

Genitalia colourless ( Fig. 20 ), with 3-segmented gonopods, limit between first and second barely visible. Unistyliger with a pointed apophysis at apeX of inner margin; first segment moderately stout, without setae; second segment with subparallel margins; third segment short, blunt, somewhat quadrangular.

Female imago ( Fig. 14 )

Measurement. Body 5.7 mm; forewing 7.1 mm.

Head. Yellowish; scape and pedicel medium to dark brown, flagellum medium brown to ecru.

ThoraX. Greyish brown, with a few diffusive yellowish maculae on pleura laterally and a few diffusive blackish maculae closed lateroparapsidal suture. Pronotum with a pair of black marks ( Fig. 14 ). Anteronotal protuberance flattened and not prominent. All legs pale whitish, with tarsi blackish. Foreleg femora with large, diffusive, brownish macula; middle and hind legs femora with small oval brownish macula. Proportions of forelegs: tibia 1.1 of femur length; tarsus shorter than tibia. Proportions of middle and hind legs: tibia 1.2–1.3 of femur length; tarsus 2.7 times shorter than tibia. Forewing ( Fig.14 ) with a dark brown base; longitudinal veins colorless eXtensively bordered with dark brown in proXimal fourth; other parts of membrane colorless; cross-veins thickened and blackish; stigmatic area with diffusive, blackish macula.

Abdomen. Abdominal terga and sterna whitish; terga III, IV, V and VII with a pair of dark brown stripes on each side; tergum V with or without a group of brownish points on each side; tergum VIII with brownish stripes distally; tergum IX with a group of brownish maculae medially ( Fig. 14 ). ApeX of sternum IX yellowish, with deep V-shape and median insertion. Cerci colourless.

Etymology. The specific epithet is named after the name of province, “Nayok”, where the type material was collected: Nakhon Nayok province in Thailand (“Nakhon” means city and is used in several province names in Thailand).

Figures

FIGURES 1–4. Female mature larva (1) and male mature larva (in alcohol) (2) of P. bishopi Müller-Liebenau, 1980 (Ratchaburi province), dorsal view; female immature larva (3) and male immature larva (in alcohol) (4) of P. nayokensis sp. nov. (Nakhon Nayok province), dorsal view.

FIGURES 11–14. Male imago (11) and female imago (12) of P.bishopi Müller-Liebenau, 1980 (Ratchaburi province), dorsal view; male imago (13) and female imago (14) of P. nayokensis sp. nov. (Nakhon Nayok province), dorsal view.

FIGURES 15–16. Forewing (15) of P. bishopi Müller-Liebenau, 1980 male imago (Ratchaburi province), dorsal view; (16) forewing of P.nayokensis sp. nov. male imago (Nakhon Nayok province), dorsal view.Scale bar = 0.5 mm.

FIGURES 17–20. Abdominal pattern (17) of P. bishopi Müller-Liebenau, 1980 male imago (Ratchaburi province), dorsal view; (18) abdominal pattern of P. nayokensis sp. nov. male imago (Nakhon Nayok province), dorsal view; (19) genitalia of P. bishopi Müller-Liebenau, 1980 male imago (Ratchaburi province), ventral view; (20) genitalia of P. nayokensis sp. nov. male imago (Nakhon Nayok province), ventral view.Scale bar = 0.5 mm (17–18), 0.2 mm (19–20).

FIGURES 21–26. P. nayokensis sp. nov., larva. (21) labrum, dorsal view; (22) labrum, ventral view; (23) glossa and paraglossa, dorsal view; (24) glossa and paraglossa, ventral view; (25) foreleg claw; (26) foreleg claw of P. bishopi Müller- Liebenau, 1980. Scale bar = 0.2 mm (21–24), 0.1 mm (25–26).

FIGURES 27–32. P. nayokensis sp. nov., larva. (27) hypopharynX, dorsal view; (28) canine and molar area of left mandible, ventral view; (29) canine and molar area of right mandible, ventral view; (30) left maXilla, dorsal view; (31) labium, ventral view; (32) marginal spines of tergite V. Scale bar = 100 µm.

FIGURES 33–36. Larva (33, arrow) and habitat (34) of P. bishopi Müller-Liebenau, 1980 (Ratchaburi province); larva (35, arrow) and habitat (36) of P. nayokensis sp. nov. (Nakhon Nayok province).