Baetiella spathae, 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 : 561-564

Baetiella spathae n. sp.

( Figs 31–44 )

Holotype. 1 mature nymph in ethanol, CHINA, Tibet, Medog County, Baibung Town (29.25°N, 95.17°E, alt. 780m), 29.ix.2010, leg. Xianfu Li.

Paratype. CHINA, Tibet: 2 nymphs on slides and 8 nymphs in ethanol, same data as holotype; 2 nymphs, Medog County, 1.x.2010, leg. Xianfu Li.

Mature nymph. Body length 3.8–4.1mm, cerci 4.2–4.5mm, median caudal filament with only one segment.

Head. Coloration light yellowish shaded with irregular brown markings on vertex and frons. Antennae light brown; dorsal surface of scape and pedicel scatter with 7–10 scale-like setae ( Fig. 31 ). Labrum rectangular ( Fig. 32 ), approximately 2.0 times wider than long, anteromedial notch shallow with a small rounded lobe at the base; each side of dorsal surface with one medial long seta and a row of 12–14 robust, simple submarginal setae sublaterally; fine and simple setae scattered posteriorly; ventrally bordered with feathered setae along the anterior margin. Left mandible ( Fig. 35 ): incisors fused, outer incisors worn out with 3 inner denticles, prostheca robust with 6 blunt and 2 acute denticles apically. Right mandible ( Fig. 36 ): incisors with visible fusion line, outer incisors worn out and inner incisors with 3 denticles, prostheca slender than the one on left mandible and with denticles apically. Hypopharynx with a median projection and superlinguae slightly truncate, covered with abundant fine setae. Maxillae ( Fig. 34 ) with three caninae and one dentiseta on crown of galealacinia, a row of 3 long basal setae and one short bristle-like hump seta on basis of galealacinia; maxillary palpus 2-segmented and subequal in length, terminal segment with a small tip at apex and slender than basal segment. Labium ( Fig. 33 ): glossae slightly shorter than paraglossae, with a row of 6–8 stout setae along the inner margin and 2 long robust blunt setae at the apex; paraglossae approximately 2.0 times wider than glossae, with two rows of stout setae ventrally and row of 3 stout acute setae near the inner margin dorsally; labial palpus 3-segmented, but terminal segment almost fused with 2nd segment; terminal segment asymmetrically conical with a small tip at apex; 2nd segment with a row of 3–4 acute setae along outer margin dorsally; dorsal surface with numerous pores on basal segment.

Thorax. Pronotum pale brown with indistinct dark brown patterns, dorsum surface without tubercles or elevations ( Fig. 43 ); posterior margin of metanotum with a single protuberance medially ( Fig. 42 ). Hind wing pads minute, approximately 2.0 times longer than wide. Thoracic sterna usually with a conical protuberance near inner side of each coxa ( Fig. 50 ). Legs paler than thorax, femora whitish shaded with light brown medially and a brown longitudinal stripe near dorsal margin; tibiae and tarsi light brown; dorsal margin of femora with dense irregular row of long, simple bristles, approximately 1/3 to 1/2 of femur width ( Fig. 37 ), as well as a pair of stout, blunt subapical setae ( Fig. 38 ) and a regular row of scale-like submarginal setae; femoral villopore present; outer margin of tibiae with irregular row of dense, fine, simple setae and a regular row of scale-like small submarginal setae; tarsi with a row of sparse, fine, simple setae dorsally; tarsal claw with a row of 7–8 denticles and a pair of bowed subapical bristles. All legs lack coxal gills.

Abdomen ( Figs. 42, 44 ). Abdominal terga generally yellowish brown, terga II–V much lighter than other segments ( Fig. 44 ). Mediodorsal posterior margin of abdominal terga I–IX each with a single protuberance, decreasing in length backwards, and vestigial on tergum IX ( Fig. 42 ); terga surface with numerous scattered small scale bases, posterior margin with blunt denticles. Abdominal sterna generally yellowish-white, each with a pair of friction pads on anterolateral area; posterior margin on sterna V–IX each with a row of continuous spatulate setae (but interrupted medially on sternum V as Fig. 39 ); setae on VI–VIII (approximately 5–6 times longer than wide) ( Fig. 40 ) slightly longer than those on V and IX (setae approximately 3–4 times longer than wide) ( Fig. 39 ). Paraproct with numerous pores on surface and 5–6 oval scale-like setae along the inner margin ( Fig. 41 ). Gills on segments I–VII, oval and without tracheation, surface scattered with numerous pores, margin smooth with fine setae and a few stout setae. Median caudal filament reduced to one segment ( Fig. 41 ), each segment of inner margin of cerci fringed with primary swimming bristles.

Imago. Unknown.

Etymology. The specific epithet, spathae (femininum), is from the Latin word, spatha (1st declension), meaning spatula, and refers to the long, flat spatulate setae on the posterior margin of abdominal sterna V–IX.

Distribution. China (Tibet).

Comments. The nymph of Baetiella spathae n. sp. appears to be most similar in appearance to B. armata Braasch, 1983 from Nepal in both having a single protuberance on terga I–IX, but the new species can be differentiated from the latter by the following diagnostic characters: (1) antennal scape and pedicel with blunt scale-like setae; (2) terminal segment of maxillary palpus with a pronounced tip (cf. Braasch 1983: fig 19); (3) 2nd segment of labial palpus almost fused with terminal segment and without inner-apical lobe, terminal segment asymmetrically conical with a small tip at apex (cf. Braasch 1983: fig 20); (4) posterior margin of sterna V–IX with close-set long spatulate setae; (5) inner margin of paraproct with a row of 5–6 oval scale-like setae (cf. Braasch 1983: fig 25).

Figures

FIGURES 31 – 40. Baetiella spathae n. sp. (31) scape and pedicel of antenna; (32) dorsal view of labrum; (33) ventral view of labium; (34) left maxilla; (35) left mandible; (36) right mandible; (37) fore-femur; (38) subapical setae of fore-femur; (39) abdominal sternum V; (40) abdominal sternum VIII.

FIGURES 41 – 44. Baetiella spathae n. sp. (41) paraprocts and median caudal filament; (42) metanotum and abdominal terga I – IX; (43) head and pronotum; (44) abdomen (dorsal view).

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).