Nigrobaetis trialbus Li & Shi & Li & Tong 2023, sp. nov.
Creators: name: Li, Bo
name: Shi, Weifang
name: Li, Xianfu
name: Tong, Xiaoli
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Baetidae
Nigrobaetis
Nigrobaetis trialbus

description: Nigrobaetis trialbus sp. nov.
(Figs 49–72)
Material examined. Holotype: male mature larva (in ethanol, deposited in SCAU), CHINA, Guizhou Province, Daozhen County, Sanqiao Town, Daqiaogou (1400m a.s.l.), 21.viii.2004, coll. Jun Wang. Paratypes: 9 larvae in ethanol and 3 specimens on mounted slides, same data as holotype.
Diagnosis of larvae. Body bicoloured. Mesonotum largely brown with a small paler oval spot near anterior margin. Fore wing pads brown with a distinct white transverse band medially. Abdominal tergites brown except tergites I, IV and VIII–X white. Right mandible with one row of fine setae along inner margin of incisors. Glossae with a cluster of 4–5 dorsal setae subapically. Hind wing pads well developed. Patella-tibial suture of foreleg present. Posterior margin of tergites I–X with triangular spines. Gills on abdominal segments I to VII. Paraproct with 9–10 pointed marginal spines.
Description of larvae. Length. Body length 5.5–6.0 mm; antennae broken; cerci incomplete. Colouration. Body bicoloured. Head yellowish with irregular brown markings. Pronotum brown; mesonotum brown except with a small paler round spot near anterior margin (Figs 49, 51). Fore wing pads brown with a distinct white band medially (Figs 49–51). Abdominal tergites brown except tergites I, IV and VIII–X white (IV and VIII with a narrow light brown band on anterior margins). All legs yellowish.
Head. Antennae close to each other, frons with a distinct median carina between bases of antennae (Fig. 52); scape and pedicel without scale-like setae, only bearing a few sparse hair-like setae. Labrum sub-rectangular (Figs 53, 60), ca. 1.4 times wider than long; anteromedian notch deep with a small rounded lobe at the base; dorsally in distal half with one long, simple seta near midline and irregular row of 5–6 medium to long, simple setae; in proximal half almost smooth, with few sparse hair-like setae on dorsal surface; ventrally bordered with feathered setae along anterior margin and 5–6 short, spine-like setae near lateral and anterolateral margin (Fig. 60). Left mandible (Figs 58, 61): incisors fused, with 8 denticles apically; prostheca robust, apically with 2 acute and 5–6 blunt denticles; margin between incisors and mola with 4 short acute spines (Fig. 51). Incisor of right mandible (Figs 54, 59, 62) fused, with 8 denticles apically; prostheca stick-like with distolateral dentation (Figs 54, 62); margin between incisors and mola with 7–8 short acute spines and one long, straight spine with distolateral pectinate (Fig. 62); one row of very fine setae along inner margin of incisors (Figs 54, 62), tuft of setae at apex of mola present. Hypopharynx (Fig. 55) apically covered with fine setae, lingua with a median projection; superlinguae slightly longer than lingua. Maxillae (Fig. 56): apex of maxillae with three canines, crown of galea-lacinia with three stout dentisetae; base of lacinia with one row of 4–5 simple setae and one short spine-like hump seta. Maxillary palp 2- segmented, ca. 1.7 times length of galea-lacinia, segment II apically rounded with hair-like setae and longer than segment I. Labium (Fig. 57) with glossae basally broad, narrowing toward apex, subequal to paraglossae in length; inner margin of glossae with 9–10 long, simple setae; apex with two long, curved, robust setae; outer margin with 7– 8 long, simple setae; ventral surface of glossae covered with sparse hair-like setae near inner margin and proximally, dorsal surface of glossae with a setal tuft of 4–5 fine setae subapically (Fig. 65). Paraglossae sub-rectangular, curved inward, ca. 1.3 times width of glossae; apex with two rows of long, robust setae in apical area; dorsally with row of 3–4 long, simple setae near inner margin. Segment I of labial palp slightly shorter than length of segments II and III combined. Segment I ventrally with sparse hair-like setae, dorsal face with a few micropores medially. Segment II slightly expanded apico-laterally, dorsal face with one oblique row of 4–5 long pointed setae (Fig. 66), ventrally with several hair-like setae. Segment III truncated apically and slightly expanded inwards; ventrally covered with 10–14 short, simple setae and numerous hair-like setae (Fig. 64), dorsally with 5–7 short, simple setae near apex and many fine hair-like setae.
Thorax. Hind wing pads well developed (Fig. 63). Femora of foreleg (Fig. 72) dorsally with one row of 8–10 long, stout setae, dorsoapical setal patch formed by 2 stout, bluntly pointed setae; ventrally with many stout pointed setae near ventral margin; anterior face with micropores and scale bases. Tibiae with a single stout, apical blunt seta on distal end of dorsal margin, ventral margin and submargin with many stout pointed, partly pectinate setae, both faces covered with many scale bases; tibiopatellar suture present. Dorsal margin of tarsi with a few hair-like setae, ventral margin with one row of 9–10 stout pointed setae (Fig. 72); both faces with numerous scale bases. Claws (Fig. 72) slender, with one row of about 12 acute teeth; subapical setae absent. Middle and hind legs similar to foreleg in structure, except tarsi with about 7 stout pointed setae along ventral margin.
Abdomen. Dorsal surface of tergites scattered with numerous trapezoidal scale bases; posterior margin of tergites I–X with triangular spines (as Fig. 28). Sternites surface covered with numerous trapezoidal scale bases, posterior margin of sternites VII–IX with triangular spines. Gills present on segments I to VII (Figs 67–70), long elliptic; margin with a light brown band and small denticles intercalating fine hair-like setae (as Fig. 25); tracheation well visible except gill I (Fig. 67); gill I slender, similar to gill VII in shape and length, gills II–VI alike in shape. Paraproct subtriangular, without posterior prolongation (Fig. 71), surface with many trapezoidal scale bases, inner margin with ca. 10 pointed spines; surface of cercotractor with some trapezoidal scale bases, margin with 13–15 blunt spines.
Alate stage: Unknown.
Etymology. The specific epithet is an arbitrary combination of “ tri- ” (derived from Latin, the prefix of three) and “ albus ” (from Latin, meaning white), referring to the larval body dorsally having three distinct white transverse bands: (1) across the median part of forewing pads (including tergite I), (2) tergite IV and (3) tergites VIII–X, which can be easily distinguished from other Nigrobaetis species in the field.
Distribution. China (Guizhou).
Discussion. This new species is most similar to N. facetus (Chang & Yang, 1994) (in Kang et al. 1994) by the abdomen with alternating brown and white (Figs 73–76), which is easily distinguished them from the other Nigrobaetis species with predominately brown abdomen. The new species was found in a high altitude (1400m a.s.l.) mountain stream in the Yunnan-Guizhou Plateau of southwestern China. In contrast, N. facetus was originally described from a lowland stream of Taiwan (Kang et al. 1994), subsequently, it was found constantly in low altitude (<200m a.s.l.) streams of the Chinese mainland (Hong Kong SAR, Guangdong and Hunan Provinces etc.). It is worth mentioning that, judging from the position of gill sockets (Kang et al. 1994: Fig. 23), Kang et al. (1994) mislabeled the abdominal tergite IV as the tergite V in the original figures because the high resolution image of original publication showed that gills I and VII still remain on their sockets. The new species can be distinguished from N. facetus by the following combination of characters: (i) labial glossae having a cluster of 4–5 thin dorsal setae subapically (Fig. 65) (vs. having 7–9 dorsal setae in N. facetus); (ii) the mesonotum largely brown with a paler small oval spot near anterior margin (Figs 49, 51) (vs. anteromedial margin of mesonotum having a large subtriangular paler patch in N. facetus); (iii) the median part of forewing pads having a distinctive transverse white band (Figs 49, 51) (versus forewing pads uniformly brown in N. facetus); (iv) hindwing pads well developed (versus absent in N. facetus); (v) posterior margin of tergite I with triangular spines (versus tergite I without such spines in N. facetus); (vi) tergite X white while the posterior half of tergite X brown in N. facetus (Figs 74–76). In addition, the new species also resembles N. arabiensis Gattolliat & Sartori, 2008 from United Arab Emirates and N. vuatazi Gattolliat & Sartori, 2012 (in Gattolliat, Vuataz & Sartori 2012) from Jordan by having 7 pairs of gills and similar colour pattern in the abdomen (Gattolliat & Sartori 2008, Gattolliat et al. 2012). But it can be separated from them by the following characters: from N. arabiensis by the presence of tibiopatellar suture and from N. vuatazi by the absence of spatulate setae on the dorsal margin of mid and hind tibiae; maxillary palp elongate, ca. 1.7 times length of galea-lacinia in the new species, while those in N. arabiensis and N. vuatazi are merely slightly longer than galea-lacinia; paraproct possessing 10 spines on inner margin in the new species, versus N. arabiensis and N. vuatazi having only 4 and 6 spines respectively.
description: Published as part of Li, Bo, Shi, Weifang, Li, Xianfu & Tong, Xiaoli, 2023, Two new species of the genus Nigrobaetis Kazlauskas (in Novikova & Kluge), 1987 (Ephemeroptera: Baetidae) from Southwest China, pp. 131-149 in Zootaxa 5315 (2) on pages 142-147, DOI: 10.11646/zootaxa.5315.2.3, http://zenodo.org/record/8130354