Bungona (Centroptella) ovata 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 : 573-575

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

( Figs 6–15 , 47 )

Material examined. Holotype. 1 mature nymph in ethanol, CHINA, Sichuan, Xuyong County, Shuiwei Town, Huagaoxi National Nature Reserve (24.20°N, 110.29°E, alt. 770m), 3.iv.2012, coll. Weifang Shi.

Paratypes (deposited in ethanol unless otherwise stated). 1 nymph on slides and 3 nymphs, same data as holotype. CHINA, Guizhou: 1 nymph on slides and 14 nymphs, Xishui County, Sanchahe Scenic , 6.viii.2011, coll. Xianfu Li ; 1 nymph, Chishui City, Foguangyan Scenic , 31.iii.2012, coll. Weifang Shi.

Description. Mature nymph. Body length 3–3.5mm, cerci 1–1.2mm, median caudal filament slightly shorter than cerci.

Colouration. Body with contrasting colour pattern ( Figs 14–15 ); vertex brown with white ecdysial line; pronotum brown with one pair of yellowish white oval markings transversely, mesonotum brown with 2 pairs of longitudinal yellowish white markings; all legs yellowish brown except for femora tinged with brown apically; abdominal tergites largely brown except for tergite I, anterior half of tergite II and tergite VIII yellow-white ( Fig. 14 ); cerci off-white to yellowish brown. Male nymph similar to female in colouration, but tergite IV with one pair of oval yellow-white markings and tergite VI with one pale brown marking medially ( Fig. 15 ).

Head. Antennae slightly longer than width of head, pedicel slightly longer than scape. Labrum rectangular ( Fig. 9 ), approximately 1.5 times as wide as long; anteromedian notch shallow with one small rounded lobe at base; dorsally each side with one median long setae and one row of 4 robust and simple submarginal setae, a few fine setae scattered posteriorly ( Fig. 9 ); ventrally bordered with feathered setae along distal margin and one distomedial arc of very fine setae. Left mandible ( Fig. 6 ): incisors fused, with 6 denticles apically; prostheca robust, apically with 2 acute and 3 blunt denticles; margin between incisors and molar region straight and without any setae. Right mandible ( Fig. 7 ): incisors partially fused, inner and outer incisors each with 3 denticles apically; prostheca slender, plumose and bifurcated at middle; margin between incisor base and molar with one spine-like seta. Hypopharynx with a median projection and superlinguae broadly truncate, covered with abundant fine setae. Maxillae ( Fig. 10 ): galealacinia with one row of 4 long basal setae and one short bristle-like hump seta basally; maxillary palpus slightly shorter than galealacinia; segment II approximately 1.6 x length of segment I. Labium ( Fig. 8 ): glossae slightly longer than paraglossae, ventrally with one row of 11–13 acute, stout setae along the inner margin and 3 robust setae at the apex, dorsally with 3–4 long, stout setae along the outer margin; paraglossae subequal to glossae in width, ventrally with one row of 3–4 acute, stout setae along the inner margin and 11–13 acute, stout setae along outer margin, dorsally scattered with 6–7 short, fine setae on basal area; segment I of labial palpus about 3/4 of the length of segment II and III combined; segment II dorsally with one row of 4 long, simple setae distomedially; segment III irregular trapezoidal and with distal margin truncated, length of inner margin approximately 1/2 of outer margin, dorsal surface smooth and ventral surface with plenty of stout and simple setae.

Thorax. Pronotum surface smooth, without tubercles. Hindwing pads minute but visible ( Fig.11 ). Leg surfaces scattered with trapezoidal scale bases. Femora approximately 4.5 x maximum width, dorsally with row of 7–8 long, robust setae (approximately 1/3 of femoral width) and one pair of stout subapical setae ( Fig. 12 ), ventrally with numerous pores; tibiae dorsally with fine setae, ventrally with one row of slightly acute stout setae and a 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, apically with 6–8 furrows; subapical setae vestigial.

Abdomen. Abdominal terga densely scattered with trapezoidal scale bases and triangular scales; posterior margin of tergites III–X with contiguous acute spines ( Fig. 13 ), successively increasing in length backwards; sternal surface scattered with trapezoidal scale bases and triangular scales; posterior margin of sternites V–IX with triangular spines; sternites II–VI each with one pair of setal tufts anterolaterally; paraproct subtriangular ( Fig. 47 ), with trapezoidal scale bases and pores medially, inner margin with 10–11 acute spines. Gills with 7 pairs, asymmetric and well tracheated ( Fig. 15 ). Median caudal filament slightly shorter than cerci, inner margin of cerci and both sides of median caudal filament fringed with swimming bristles.

Imagoes. Unknown.

Etymology. The specific epithet “ ovata ” is from Latin adjective “ovatus”, meaning “oval”, in reference to the pro- and mesonotum having oval yellowish markings.

Distribution and biology. China (Guizhou, Sichuan). The nymphs are usually found in slow to moderately rapid mountain streams with cobble and gravel substrates.

Comments. Nymph of B. ovata sp. nov. is superficially similar to B. longisetosa , but it can be easily distinguished from the latter by following characteristics: (1) pro- and mesonotum having oval yellowish markings, while those in B. longisetosa are almost uniformly brown; (2) abdominal tergite I and anterior half of tergite II yellow-white (vs. tergites I–II largely brown in B. longisetosa ); (3) maxillary palpus subequal to galealacinia in length (vs. only about 1/2 length of galealacinia in B. longisetosa ); (4) segment II of labial palpus dorsally with one row of 4 long, simple setae apicomedially, distal margin of segment III truncated (vs. segment II dorsally with row of 3 long, simple setae apicomedially and segment III trapezoidal in B. longisetosa ).

Figures

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).

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