Bungona (Centroptella) quadrata Shi & Tong, 2019

Shi, Weifang & Tong, Xiaoli, 2019, Genus Bungona Harker, 1957 (Ephemeroptera: Baetidae) from China, with descriptions of three new species and a key to Oriental species, Zootaxa 4586 (3), pp. 571-585 : 575-577

Bungona (Centroptella) quadrata Shi & Tong , sp. nov.

( Figs 16 –31,48)

Material examined. Holotype. 1 mature nymph in ethanol, CHINA, Guangxi, Jinxiu County, Fenzhan (24.12°N, 110.21°E, alt. 779m), 16.xi.2011, coll. Weifang Shi.

Paratypes (deposited in ethanol unless otherwise stated). 2 nymphs on mounted slides and 1 nymph, same data as holotype; CHINA. Guangxi: 3 nymphs, Wuming County, Daming Mountain (23.52°N, 108.34°E, alt. 830m), 8.ix.2011, coll. Weifang Shi. Guangdong: 1 nymph on mounted slides and 1 nymph, Heyuan City, Yequgou Scenic (23.71°N, 114.62°E, alt. 210m), 14.ix.2011, coll. Weifang Shi. 2 nymphs, Yingde City, Shimentai Nature Reserve, Hengshitang (24.43°N, 113.31°E, alt. 810m), 2.xi.2011, coll. Weifang Shi.

Description. Mature nymph. Body length 3.3–3.7mm, cerci 1.3–1.7mm, median caudal filament slightly shorter than cerci.

Colouration. Vertex brown with white ecdysial line. Thorax pale brown shading to brown smudges on pro- and mesonotum; femora pale brown shaded with one brown marking submedially, tibiae and tarsus pale brown with dark brown proximally. Abdominal tergites almost uniformly brown ( Fig. 31 ). Cerci cream to yellowish brown.

Head. Antennae approximately 1.3 x width of head, pedicel approximately 2 x length of scape ( Fig. 16 ). Labrum ( Fig. 17 ): rectangular, width approximately 1.6 x length; anteromedian notch shallow with one small rounded lobe at base; dorsally each side with one medial long seta and one row of 3–4 robust and simple submarginal setae, fine and simple setae scattered posteriorly; ventrally bordered with feathered setae along distal margin and one disto-medial arc of very fine setae. Left mandible ( Fig. 19 ): incisors fused, apically with 6 denticles; prostheca robust with 2 acute and 3 blunt denticles apically; plane of mandible between incisor base and molar region smooth. Right mandible ( Fig. 20 ): incisors partially fused, inner and outer incisors with 3+3 denticles respectively; prostheca slender, plumose and bifurcated at middle; plane of mandible between incisor base and molar region smooth. Hypopharynx with one median projection and superlinguae broadly truncate, covered with abundant fine setae. Maxillae ( Fig. 21 ) with one row of 4 long basal setae and one short bristle-like hump seta on basis of galealacinia; maxillary palpus 2-segmented, weakly shorter than galealacinia, segment II pointed apically, approximately 2.0 x length of segment I. Labium ( Fig. 18 ): glossae slightly longer than paraglossae, ventrally with one row of 10–12 acute, stout setae along the inner margin and 4 robust setae at the apex, dorsally with 5–6 long, stout setae along the outer margin; paraglossae ventrally with one row of 5–6 acute, stout setae along the inner margin and 11–13 acute, stout setae along the outer margin. Labial palpus 3-segmented; segment I subequal to segment II and III combined in length, scattered with numerous pores dorsally and fine setae ventrally; segment II slightly projected apically, dorsal surface with one row of 3 long, acute setae apicomedially, ventrally scattered with numerous fine, simple setae; terminal segment rectangle, scattered with plenty of stout, simple setae ventrally.

Thorax. Pronotum surface smooth without tubercles. Hindwing pads minute but visible ( Fig. 22 ). Leg surfaces scattered with trapezoidal scale bases. Femora approximately 4.5 x maximum width, dorsally with row of about 6 long, robust setae which approximately 1/3–1/4 of femoral width and one pair of close-set stout subapical setae ( Fig. 27 ), ventrally with numerous pores; tibiae ( Figs 23–25 ) dorsally with fine setae, ventrally with one row of slightly acute stout setae and one pair of long, stout, slightly feathered setae apically; tarsi dorsally with fine setae, ventrally with one row of slightly acute stout setae. Claw smooth without denticles ( Fig. 26 ), apically with 3–4 furrows; subapical setae vestigial.

Abdomen. Abdominal tergal surface scattered with scale bases and triangular scales densely ( Fig. 28 ). posterior margin of tergites II–X with contiguous acute spines, successively increasing in length backwards; sternal surface scattered with numerous scale bases and pores; sternites IV–IX with triangular spines posteriorly ( Fig. 29 ); sternites II–VI each with one pair of setal tufts anterolaterally; paraproct ( Fig. 48 ) subtriangular, surface scattered with trapezoidal scale bases and triangular scale densely, inner margin with 8–9 long and pointed spines. Gills with 7 pairs, asymmetric and well tracheated ( Fig. 31 ). Median caudal filament slightly shorter than cerci; inner margin of cerci and two sides of median caudal filament fringed with long swimming bristles; distal margin of each segment with trapezoidal scale bases and every two segments with long, stout spines distally ( Fig. 30 ).

Imagoes. Unknown.

Etymology. The specific epithet “ quadrata ” is from Latin adjective “quadratus”, meaning “rectangular” and referring to the terminal segment of labial palpus rectangle-shape.

Distribution and biology. China (Guangxi, Guangdong). The nymphs are usually found on the stone surfaces in shallows or lentic habitats of mountainous streams.

Comments. Compared with other species of the subgenus Centroptella whose body with relatively contrasting colour pattern, this new species is easily recognized by the body coloration relatively uniformly brown. Apart from that, this new species is somewhat similar to B. (C.) ovata sp. nov. in structure, but it can be separated from the latter by (1) antennal pedicel much longer, approximately 2 x length of scape ( Fig. 16 ); (2) terminal segment of labial palpus rectangular ( Fig. 18 ) instead of irregular trapezoidal and with distal margin truncated ( Fig. 8 ); (3) posterior marginal spines present on tergites II–X, while such spines present on tergites III–X in B. (C.) ovata sp. nov..

Figures

FIGURES 16–26. Nymph of Bungona (Centroptella) quadrata sp. nov. (16) antenna; (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) fore tibia; (24) mid tibia; (25) hind tibia; (26) claw.

FIGURES 27–31. Nymph of Bungona (Centroptella) quadrata sp. nov. (27) foreleg; (28) abdominal tergum VIII; (29) abdominal sterna IV–IX; (30) cerci; (31) habitus of female nymph (dorsal view).

FIGURES 47–49. Paraprocts (47) Bungona (Centroptella) ovata sp. nov.; (48) Bungona (Centroptella) quadrata sp. nov.; (49) Bungona (Chopralla) bifida sp. nov.

FIGURES 6–15. Nymph of Bungona (Centroptella) ovata sp. nov. (6) left mandible; (7) right mandible; (8) labium (left: dorsal view; right: ventral view); (9) dorsal view of labrum; (10) left maxilla; (11) metanotum; (12) foreleg; (13) abdominal terga VIII–X; (14) habitus of female nymph (dorsal view); (15) habitus of male nymph (dorsal view).