Baetiella sexta, Shi, Weifang & Tong, Xiaoli, 2015

Shi, Weifang & Tong, Xiaoli, 2015, Taxonomic notes on the genus Baetiella Uéno from China, with the descriptions of three new species (Ephemeroptera: Baetidae), Zootaxa 4012 (3), pp. 553-569 : 559-561

Baetiella sexta n. sp.

( Figs. 15–30 )

Holotype. 1 mature nymph in ethanol. CHINA, Sichuan, Xuyong County, Huagaoxi National Nature Reserve, Shuiwei Town (28.27°N, 105.54°E, alt. 510m), 3.iv.2012, leg. Weifang Shi.

Paratypes (deposited in ethanol unless otherwise stated). CHINA, Hubei: 33 nymphs, Yichang, Yiling District, Dalaoling Forest Farm, Letian Stream (31.06°N, 110.93°E, alt. 1,590m), 5.v.2007, leg. Bin Zhang; Sichuan: 1 nymph on slides and 170 nymphs in ethanol, same data as holotype; 35 nymphs, Tianquan County, Lianglu Town, Qiandiaoqiao Bridge (29.97°N, 102.43°E, alt. 1,260m), 15.vii.2004, leg. Sanbao Tang; 161 nymphs, Tianquan County, Lianglu Town, Erlangshan National Nature Reserve, Baichaping (29.90°N, 102.38°E, alt. 1,570m), 17.vii.2004, leg. Sanbao Tang; 24 nymphs, Luding County, Moxi Town, Gongga Mountain National Nature Reserve (29.84°N, 102.03°E, alt. 3,030m), 20.vii.2004, leg. Sanbao Tang; 57 nymphs, Pingwu County, Laohegou Nature Reserve (32.53°N, 104.69°E, alt. 1,950m), 23.v.2012, and 51 nymphs, the same locality but collected on 4.v.2013 and 6.v.2013, leg. Weifang Shi; Chongqing: 1 nymph, Wulong County, Tiekuang Rown, Dada (29.22°N, 107.41°E, alt. 1,030m), 25.viii.2004, leg. Jun Wang; Guizhou: 57 nymphs, Daozhen County, Dashahe Nature Reserve (29.18°N, 107.56°E, alt. 1,050m), 25.viii.2004, leg. Jun Wang; 8 nymphs, Suiyang County, Qinggangtang Town, Baishao (28.29°N, 107.18°E, alt. 820m), 27.iii.2012, leg. Weifang Shi; 6 nymphs, Chishui, The Chinese Jurassic Park (28.44°N, 106.00°E, alt. 420m), 31.iii.2012, leg. Weifang Shi.

Mature nymph. Body length 4.5–5.5mm, cerci 5.0–6.0mm, median caudal filament with 3 segments.

Head. Capsule brown with irregular dark brown markings on vertex and frons ( Fig. 30 ). Antennae light brown, approximately 1.5 times the width of head; dorsal surface of scape and pedicel scatter with fine setae ( Fig. 15 ). Labrum slightly rectangular ( Fig. 17 ), approximately 2.0 times wider than long; anteromedian notch deep with a small rounded lobe at the base, and each side with one medial long seta and a row of 8–10 robust, simple submarginal setae, fine and simple setae scattered posteriorly; ventrally bordered with feathered setae along the anterior margin. Left mandible ( Fig. 19 ): incisors fused with 7 denticles, prostheca robust with 4 blunt and 3–4 acute denticles apically. Right mandible ( Fig. 20 ): incisors with visible fusion line, outer incisors with 3 denticles and inner incisors with 4 denticles, inner incisor margin smooth without fine setae, prostheca with denticles apically and distinctly more slender than the one on left mandible, edge between prostheca and molar smooth with no serration, molar plated-like. Hypopharynx ( Fig. 16 ) with lingua rounded and superlinguae broadly truncate, covered with abundant fine setae. Maxillae ( Fig. 21 ) with three caninae and one dentiseta on crown of galealacinia, a row of 4–5 long basal setae and basis of galealacinia without hump seta; maxillary palpus 2-segmented and subequal in length, terminal segment with a small tip at apex. Labium ( Fig. 18 ): glossae shorter than paraglossae, with a row of 10–13 stout setae along the inner margin dorsally and 2 long robust blunt setae at the apex; paraglossae approximately 2.0 times wider than glossae, with 3 rows of setae ventrally and 4–5 stout acute setae along the inner margin dorsally; labial palpus 3-segmented, terminal segment conical with a distinctive tip at apex; the 2nd segment with an inner-apical lobe and a row of 4–6 setae along the outer margin; dorsal surface with numerous pores on the basal segment.

Thorax. Coloration pale brown with indistinct darker patterns. Surface of pronotum with 2 pairs of oblique stripes ( Fig. 30 ). Posterior margin of metanotum with a finger-like protuberance medially ( Fig. 29 ). Hind wing pads reduced, approximately 2.5–3.0 times longer than wide ( Fig. 22 ). Thoracic sterna usually with a conical protuberance near inner side of each coxa (cf. Fig. 50 ). Legs slightly paler than thorax, femora creamy shaded with light brown medially and a brown longitudinal stripe near dorsal margin, tibiae and tarsi brown. Femora with a row of long, robust and simple bristles on dorsal margin ( Fig. 23 ), femoral villopore present; tibiae with irregular row of dense, fine, simple setae dorsally; tarsi with a row of sparse, fine, simple setae dorsally and a row of 7–8 robust, pointed setae ventrally increasing in length towards apex; tarsal claw with a row of 6–7 denticles and a pair of bowed subapical bristles ( Fig. 24 ). All legs lack coxal gills.

Abdomen. Generally yellowish-brown. Abdominal terga I–IX light brown each with a pair of dark brown elongate-oblique medioanterior sigilla (cf. Kluge & Novikova 2011), terga VII–IX each with a pair of dark brown roundish medioposterior sigilla, and tergum X with pair of longitudinal brown stripes near median line ( Fig. 29 ). Mediodorsal posterior margin of terga I–VI each with a single protuberance which successively decreasing in length backwards ( Figs 25 , 28, 29 ); terga surface scattered with round scale-like and fine setae, posterior margin with blunt denticles. Abdominal sterna generally yellowish-white, each with a pair of friction pads on anterolateral area; posterior margins of sterna I–VII smooth without any denticles or scale-like setae, but sterna VIII–IX with blunt denticles ( Fig. 26 ). Gills on segments I–VII, oval and without tracheation, surface scattered with numerous pores, margin smooth with fine simple setae, coloration white or reddish depending on the type of habitats. Paraproct with numerous pores and fine short setae medially and 14–18 serrations on inner margin. Median caudal filament with 3–5 segments ( Fig. 27 ), each segment of cerci on inner margin with 2–5 swimming bristles (increasing in number towards apex).

Imago. Unknown.

Etymology. The specific epithet, “ sexta ” (feminine), is from the Latin adjective, sextus, meaning sixth, in reference to the posteromedial margin on terga having a single protuberance from the first tergum to the sixth tergum.

Distribution. China (Hubei, Sichuan, Chongqing, Guizhou).

Comments. Baetiella sexta n. sp. is most similar to B. lanpingensis n. sp. by sharing the posteromedian margin on terga I–VI each with a single dorsal protuberance, but it can be readily distinguished from the latter by the following combination of characteristics: (1) dorsal surface of scape and pedicel scatter with fine setae and without scale-like setae; (2) 2nd segment of labial palpus with an apparent inner-apical lobe; (3) posterior margins of sterna I–VII smooth without any spines or scale-like setae; (4) median caudal filament 3–5 segments.

Figures

FIGURES 15 – 26. Baetiella sexta n. sp. (15) scape and pedicel of antenna; (16) hypopharynx; (17) dorsal view of labrum; (18) labium (left: dorsal view; right: ventral view); (19) left mandible; (20) right mandible; (21) right maxilla; (22) metanotum; (23) mid-femora and tibia; (24) fore-tarsus and claw; (25) abdominal tergum V; (26) abdominal sternum VIII.

FIGURES 27 – 30. Baetiella sexta n. sp. (27) median caudal filament; (28) abdominal terga VI – VIII; (29) habitus of female nymph; (30) dorsal view of head and thorax.

FIGURES 45 – 54. Baetiella spp. from China. (45) B. bispinosa (Gose); (46 – 47) dorsal and lateral view of B. macani (Muller- Liebenau); (48) B. marginata Braasch; (49) coxal gills of B. macani (Muller-Liebenau); (50) thoracic sterna of B. spathae n. sp.; (51) thoracic sterna of B. tuberculata (Kazlauskas); (52) head and thorax of B. marginata Braasch; (53) B. trispinata Tong & Dudgeon; (54) B. tuberculata (Kazlauskas).