Ameletus daliensis Tong, 2021

Li, Xianfu, Luo, Yanping, Jiang, Jian, Wang, Lili & Tong, Xiaoli, 2021, Description of a new species of the genus Ameletus Eaton, 1885 (Ephemeroptera, Ameletidae) from Yunnan, China, ZooKeys 1021, pp. 37-51 : 37

Ameletus daliensis Tong sp. nov. Figs 2-3 , 4-19 , 20-25 , 26-29 , 30-34 , 35-39

Material examined.

Holotype: male mature larva (in ethanol, deposited in BMDU), China, Yunnan Province, Dali City, Mt. Cangshan, Mocan Stream (2020 m a.s.l.), 15.v.2020, coll. Xianfu Li. Paratypes (in ethanol, one male imago reared from larva and one larva are deposited in BMDU, the remaining in SCAU): 14 larvae and two imagos reared from larvae with same data as holotype; 20 larvae, one female sub-imago and one male imago reared from larvae, Yunnan, Dali City, Mt. Cangshan, Heilong Stream (2220 m a.s.l.), 1.v.2018, coll. Xianfu Li ; one male sub-imago, Dali City, Mt. Cangshan, Heilong Stream , 28.v.2019, coll. Xianfu Li.

Diagnosis.

Larva has the following combination of characters: 1) body with contrasting colour pattern; 2) labrum ventrally bordered with row of dense feathered setae (rare bi-forked setae) along anterior margin; 3) inner margin of trochanter in hind leg bearing row of brush-like fine and dense setae; 4) abdominal tergites I-X each with pointed spines on posterior margin; sternites without any spines on posterior margin, except V-VIII with tiny spines laterally; sternite IX with deep V-shaped cleft in both sexes. Sub-imago. 1) labial and maxillary palpi present and clearly visible; 2) wings semi-transparent, all cross-veins bordered around by dark brown. Imago. 1) labial and maxillary palpi present, but vestigial; 2) forewing transparent, MP 2 turns downwards to meet CuA, stigmatic area suffused with milky and divided by a longitudinal vein; hind wings hyaline with short costal projection near the base; 3) genital forceps dark brown, apices of lobes round and slightly bent inwardly, ventral plates absent.

Description.

Mature larva (in ethanol) (Figs 2 , 3 ). Body length 14 (12.5-15.0) mm; cerci 7 (6.0-7.5) mm. Head brown, except ocelli pale. Eyes blackish-grey. Antenna brown dorsally at base, flagellum light brown. Clypeus brown; labrum mainly brown with two longitudinal dark brown stripes submedially. Pronotum dark brown with light brown irregular markings and one pale mesal line, meso- and metanotum brown with some irregular dark brown streaks and markings. Legs largely brown, except femora with pale patches on sub-basal and sub-distal areas, tarsi dark brown near apex. Abdominal tergites with contrasting colour pattern, tergite I white with diffuse light brown in a form of triangle medially, tergites II-III and VI-VII white, each with pair of diffuse light brown longitudinal bends sub-medially, tergites IV-V and VIII-IX mainly brown, each with longitudinal pale stripe medially, tergite X white with brown along posterior margin and pair of longitudinal light brown streaks; tergites II-IX each with pair of dark brown oblique stripes sub-medially and pair of dark brown stripes on sides; abdominal sternites brown, except sternites I, VI, VII and IX paler; sternites II-VIII each with ganglionic marking medially (Fig. 3 ), II-IX each with pair of small pale spots on anterolateral corners. Generally, the above colour pattern can change slightly in intensity, depending on the life stage.

Head. Flagellum of antenna with approximately 15-17 segments. Labrum (Fig. 4 ) rectangle (length to width ratio approximately 0.7:1) with shallow indentation on anterior margin, ventrally bordered with row of dense feathered setae (rarely bi-forked setae) along anterior margin. Outer incisor of left mandible with 4 denticles, first denticle longest, rest gradually getting shorter; outer incisor of right mandible with 3 denticles (Fig. 5 ), first denticle longest, second denticle slightly shorter or subequal to third. Hypopharynx as in Fig. 11 , lingua with one median projection covered with hair-like fine setae. Right and left maxillae similar in structure (Fig. 6 ), crown of each maxilla with 27-31 comb-shaped setae and first seta with approximately 20 pointed denticles (Fig. 8 ), lateral galealacinia with row of approximately 14 long, feathered setae; maxillary palp 3-segmented, length ratio from basal to apical segments = 2.3:1.4:1, apex of terminal segment with one small hook (Fig. 7 ). Apical margin of glossae truncate and straight with row of long, spatulate flat setae widened towards apex (Fig. 9 ).

Thorax. Dorsal surface of legs covered with many minute spine-like setae; apices of femora with crosswise row of distinct stout spine-like setae (Fig. 12 ): fore, middle and hind femora with 7-8, 4-5 and 3 stout setae at apices, respectively. Claws slightly curved and without denticles (Fig. 10 ). Inner margin of trochanter in hind leg bearing row of brush-like fine and dense setae (Fig. 23 ), fore and middle trochanters without such setae.

Abdomen. Tergites I-X each with pointed spines on posterior margin (Figs 20 , 22 ); sternites I-IV without any spines on posterior margin, V-VIII with tiny spines (Fig. 21 ) on posterior margin laterally (visible only under high magnification); surfaces of tergites and sternites I-IV without spine-like setae, but V-IX covered with tiny spine-like setae (Fig. 20 ), sternite IX with deep V-shaped cleft in both sexes, female with acute dentate emargination medially (Fig. 24 ), male without any denticles, penis buds without spine-like setae (Fig. 25 ); posterolateral spines on abdominal segments VIII-IX relatively short. Gills on abdominal segments I-VII (Figs 13-19 ); gills I-II white and oval, widest at apical half, each with short costal and anal ribs (Figs 13 , 14 ); gills III-VII white with brown ribs and black tracheae, each with one strong costal rib and distinct serrations on costal margin and with one strong anal rib far from anal margin (Figs 15-19 ). Ratios of maximum width to length: gill I = 0.71, gill II = 0.66, gills III-IV = 0.48, gill V-VI = 0.50 and VII = 0.45. Cerci dark brown and median caudal filament paler (Figs 2 , 3 ).

Male imago (in alcohol). Length (mm): Body 13 (12.5-14.0); forewings 12 (11.5-12.5); cerci 19 (16.0-22.0).

Head. Upper portion of compound eyes grey, lower portion dark grey (Figs 26 , 27 ). Antennae light brown. Ocelli whitish. Labial and maxillary palpi present, but vestigial. Thorax: Pronotum dark brown. Anteronotal protuberance brown, posterolateral sides dark brown; medioscutum brown, submedioscutum dark brown, median longitudinal suture dark brown (Fig. 27 ); sublateroscutum brown to dark brown; posterior scuttle protuberance brown with narrow white patch posterolaterally; scutellum brown, infrascutellum dark brown, scuto-scutellar impression light brown with pale lateral margins. Foreleg dark brown, except light yellowish-brown at basal 1/3 of femur (Fig. 32 ); middle and hind legs similar in colour and lighter than forelegs (Figs 33 , 34 ); tibia pale and tarsus light brown, dorsal surface without spinules. Length of foreleg segments (mm): femur 2.7; tibia 2.7; tarsal segments 0.8, 1.7, 1.6, 1.1 and 0.5. Fore wings membrane transparent (Fig. 30 ), all veins dark brown with cross-veins lighter. Vein RS forked at about 1/4 of distance from base to margin; MA forked at middle of wing; MP 2 turns downwards to meet CuA; stigmatic area suffused with milky and divided by longitudinal vein; cross-veins between C and R veins bordering around by dark brown. Hind wings hyaline with short costal projection near the base; vein MA forked at middle with one intercalary vein between MA1 and MA2; MP forked about one-third of distance from base to margin (Fig. 31 ).

Abdomen: Tergites I and X brown, tergites II-IX brown with two triangle-like white markings on anterior half (Fig. 27 ). Sternites II-VIII pale, each with ganglionic marking medially. Cerci dark brown.

Genitals: Styliger white with brown markings laterally (Fig. 35 ); forceps dark brown, terminal segment paler (Fig. 35 ); penis lateral lobes with spinules, apices of lobes round and slightly bent inwardly; ventral plates absent (Figs 36-39 ).

Female subimago (in alcohol). Length (mm): Body 13.5; forewings 13.5; cerci 11. Compound eyes dark grey. Lateral view of head, the labial and maxillary palpi present and clearly visible (Fig. 28 ). Pronotum pale. Medioscutum and median longitudinal suture pale to light brown; submedioscutum and sublateroscutum brown. Wings semi-transparent, all cross-veins bordered around by dark brown. Abdominal tergite I pale with brown markings laterally and medially, colour pattern of other tergites similar to those of male; sternites II-VIII pale, each with blackish ganglionic marking medially, subgenital plate brown with deep V-shaped cleft.

Eggs. Generally long ellipsoid shape with length 180-205 μm and width 100-115 μm (Fig. 29 ). The chorionic surface is covered by large-mesh polygonal cells, each cell with a small protuberance in the middle; large prominent round knobs exist on one pole only.

Etymology.

The specific epithet is named after the type locality, Dali City , Yunnan Province, China .

Distribution.

China (Yunnan).

Biology.

Larvae of this new species prefer to live in pools or slow currents with boulder and cobble substrate in very clear small streams. At one representative location (Heilong Stream, Mt. Cangshan) in May, the average water temperature was 14.6 °C, pH was 6.9 and DO (mg/l) was 7.6. Mature larvae with black wing-pads could be collected from early May through to mid-July, which suggests that the emergence period of the alate stage occurs from early May to late July, from which we infer that A. daliensis Tong, sp. nov. is a univoltine species in Dali, Yunnan. Before emergence, the mature larvae crawled to stones protruding from the water, half submerged and moulted to sub-imago (Fig. 42 ). The sub-imagos usually emerged on a warm sunny daytime and were rarely collected by light-trap in the evening.

Figures

Figures 2, 3. Larval habitus of Ameletus daliensis Tong, sp. nov. 2 dorsal view (upper: female; lower: male) 3 ventral view (upper: female; lower: male).

Figures 4 - 19. Larva of Ameletus daliensis Tong, sp. nov. 4 labrum (dorsal view) 5 right mandible 6 right maxillae 7 apex of terminal segment of maxillary palp (showing hook) 8 comb-shaped setae of maxilla (showing first seta) 9 labium 10 claw 11 hypopharynx (left: ventral view; right: dorsal view) 12 femur of foreleg 13 - 19 gills I-VII.

Figures 20 - 25. Larva of Ameletus daliensis Tong, sp. nov. 20 abdominal tergites VII-VIII 21 sternite VIII 22 abdominal tergite X (male) 23 trochanter of hind leg 24 female sternite IX 25 male sternite IX (showing penis buds, ventral view).

Figures 26 - 29. Ameletus daliensis Tong, sp. nov. 26 male imago 27 male imago (dorsal view) 28 head of male sub-imago 29 egg (SEM).

Figures 30 - 34. Imago of Ameletus daliensis Tong, sp. nov. 30 forewing 31 hind wing 32 fore leg 33 middle leg 34 hind leg.

Figures 35 - 39. Male genitals of Ameletus daliensis Tong, sp. nov. 35 terminal abdominal sternites 36 penis lobes 37 penis lobes (ventral view) 38 penis lobes (dorsal view) 39 penis lobes (lateral view).

Figures 40 - 42. 40 rearing cage in the field 41 rearing cage 42 habitat of Ameletus daliensis Tong, sp. nov.