Monodiamesa secunditibetica Han and Tang, 2021

Han, Wu, Tang, Hongqu & Ni, Zhenyu, 2021, DNA barcodes and morphology reveal two new species of Monodiamesa Kieffer (Diptera: Chironomidae: Prodiamesinae) in Tibetan Plateau, Zootaxa 4990 (1), pp. 81-103 : 84-91

Monodiamesa secunditibetica Han and Tang , sp. n.

( Figs. 3–5 )

http://zoobank.org/ urn:lsid:zoobank.org:act:51B08247-C1BD-4791-93AD-A66A86D865A8

Material examined. Holotype: 1 male [Voucher No: Mon_03], CHINA: Tibet Autonomous Region, Shigatse Municipal, Zhongba County, Taro Co , 31°6'4.1'' N, 84°1'12'' E, alt. 4567 m, 28.viii.2020, hand net, H.Q. Tang . Paratypes: 1 female [Voucher No: Mon_04] as previous, 2 males [Voucher No: Mon_05, Mon_06], CHINA: Tibet Autonomous Region, Shigatse Municipal, Zhongba County, Ngangla Ringco , 31°33'35.9'' N, 84°05'25.6'' E, alt. 4716 m, 30.viii.2020, draft net ; 2 males, 2P/m, 2 Pe / Le, [Voucher No: TB_81, NM_01, NM_02], CHINA: Tibet Autonomous Region , Lhasa , Dangxiong County, Namco, 31°47'54.6'' N, 90°57'4.9'' E, alt. 4724 m, 09.ix.2019, drift net, W. Han .

Etymology. secund-, from Latin, means second, following; tibetica refers to the type locality. The epithet suggests it was the second Monodiamesa species found in Tibet, but also alludes to its discovery during the Second Expedition Program of Tibetan Plateau.

Diagnostic characters. Adult male. AR 2.65–2.88, clypeus with 2–5 setae; subapex of gonostylus expanded; length of apical spine of MVo great longer than the basal sclerotized pedestal.

Adult female. AR 0.50–0.56, clypeus with 4–6 setae. Gonocoxapodeme curved smoothly, S VIII with some short setae (30–40 μm) arising from the small pale pits (diameter 10–15 μm). Gonocoxite IX relative stout, inner lateral margin partial fused with S IX. T IX with 8–14 setae on each ovate protrusion.

Pupa. Prealar tubercle weakly sclerotized, with distinct numerous wrinkles on the pale-yellow surface. Male genital sac seldom extending the distal margin of anal lobe.

Larva. Mentum slope less steep, pigmentation of median mentum teeth similar to the lateral teeth; insertion of two genal setae relatively distant from the ventromental plate.

Male (n = 4, Fig. 3 ).

Total length, 5.80–6.75, 6.18 mm. Wing length, 3.20–3.85, 3.45 mm; wing width, 0.92–1.05, 0.96 mm.

Colour. Generally brown to dark brown, antenna with dark scape and yellow to brown flagellum. Thorax general dark brown, with imperceptible dark vittae, scutellum and pleurae yellow to brown. Haltere pale yellow. Legs yellow except for coxa, trochanter and joint parts of each segment. Wing bright glassy, without smokey punctation. Abdomen tergite general dark brown, sternite brown with longitudinally median brown patches in S I–V.

Head. Eyes bare, extending parallel-sided dorsomedial with truncated terminals, separated by 6 x its terminal width. Flagellomere 1–12, 400 μm (2); flagellomere 13, 1000–1150 μm (2); AR 2.65–2.88 (2). Palpomere 1–5 lengths (in μm): 75–100, 83; 80; 160–210, 188; 150–180, 165; 210–250, 234; the fourth palp shorter than the adjacent two segments, Palp4/Palp3, 0.83–0.94, 0.88. Temporals 11–15, 12. Clypeus ( Fig. 3B ) with 2–5, 4 setae.

Thorax. Humeral pit distinct. Dorsocentrals 14–17, 15, uniserial. Antepronotals 5–7. Scutellum with 16–18 setae, fairly two rows. Prealars 5–7, 6 in a straight line.

Wing. Anal lobe developed, projected basally. Squama with 41–51, 45 (3) setae, partly biserial. Crossvein MCu longer than oblique RM and its distance to RM and FCu; RM 80–100, 93 μm long; MCu 100–150,133 μm long; RM/MCu, 0.67–0.80, 0.71.

Legs. Fore tibia with one spur, 85–100, 95 μm long; spurs of middle tibia subequal, 50–70, 66 μm long; spurs of hind tibia unequal, 63–75, 68 μm (3) and 90–100, 97 μm (3) respectively, the long spine with side teeth in basal 1/3. Hind tibial comb with 11–14, 13 long spines, arranged in V-shape. Ta 1 and Ta 2 in the mid- and hind legs each with 2 subequal pseudospurs subapically, 33–40, 36 μm. LR 1, 0.77–0.82, 0.80 (3); LR 2, 0.45–0.47, 0.46; LR 3, 0.56–0.61, 0.58. BV 1, 2.38–2.65, 2.48 (3); BV 2, 2.83–3.03, 2.91; BV 3, 2.48–2.72, 2.56. BR 1, 3.0–3.8 (2); BR 2, 3.2–3.5 (2); BR 3, 4.0–4.5 (2).

Abdomen. Distinctly setiferous in general appearance, covering near total surface but particular dense laterally. Anterolateral corner of tergite I with hairy pale oval. T I –VIII with dense setae, subquadrate in general. S I–V with V-shape muscle marks.

Hypopygium. ( Figs. 3A, 3E, 3F ) T IX with 8–13, 10 setae at each posterolateral corner. Anal point triangular shape, each side with 5–7 setae. Gonocoxite 325–350, 330 μm long, inner margin with 6–9 distinct setae, 50–65 μm long. Superior volsella foot-shaped, dorsal surface with inward-oriented macrotrichiae. Inferior volsella with stout neck gradually broad to scallop-like apical part, subequal to ends of superior volsella; both surfaces of apical part with numerous radially arranged macrotrichiae and 5–7 prominent setae only at dorsal surface. Median volsella ( Fig. 3C ) with cylindrical base, 8–10, 8.7 μm wide, 16.8–25.0, 20.7 μm long and flexural digitus, 51–72, 66.8 μm long. Basal median lobe ( Fig. 3D ) developed, trapezoid-shaped, near inner margin with 1 or 2 tubercular setae, 35–45, 40 μm long. Gonostylus expanded subapically, 145–150, 198 μm long, 50 μm wide at subapex; megaseta prominent, 11.2–16.0, 14.4 μm long, with two subapical stiff setae. HR, 2.00–2.33, 2.21. HV, 3.87–4.13, 4.15.

Female. (n = 3, Fig. 4 )

Total length 4.15–5.70, 5.45 mm. Wing length 3.65–3.75, 3.70 mm, width 0.80–0.85, 0.82 mm.

Colour. Thorax generally yellowish brown, three vittae distinctly separated from the ground color. Scutellum and pleurae light yellow. All legs uniformly brown. Abdomen with similar color pattern as adult male. Spermatheca dark brown.

Head. Eyes extending dorsomedially, ending in wedge-shaped terminals, separated by 8–9 x its terminal width. Antenna ( Fig. 4B ) 6-segmented, last flagellomere 195–230, 220 μm. AR 0.50–0.56, 0.54. Temporals 5–7, 6, clypeals 4–6, 5. Palpomere 1–5 lengths (in μm): 45 –50; 65–80; 130–155; 125–100; 220–240 (n = 2), palp 4 shorter than the neighboring segments.

Thorax. Antepronotals 8–10, 7. Dorsocentrals 9–13, 11, in a single row. Scutellars 15–21, 19, arranged in three rows. Prealars 5–7, 6.

Wing. Squama with 40–51, 43 setae, robust biserial. Crossvein MCu longer than oblique RM and its distance to RM and FCu; RM 140 μm long; MCu 160 μm long; RM/MCu 0.88.

Legs. Fore tibia with one spur, 65–80, 76 μm long; spurs in middle tibia subequal, 50–70, 63 μm long; spurs in hind tibia unequal in length, 90–100, 95 μm and 60–65, 63 μm, respectively. Hind tibial comb with 9–12, 11 long spines, lateral spines distinctly longer than the middle one, concave medially in a V shape. Two pseudospurs on apical part of each Ta 1 and Ta 2 of mid- and hind legs 25–30, 28 μm long. LR 1, 0.72–0.73 (2); LR 2, 0.43–0.44 (2); LR 3, 0.56–0.60 (2). BV 1, 2.46–2.74 (2); BV 2, 3.00–3.10 (2); BV 3, 2.70–2.72 (2). SV 1, 2.47–2.56 (2); SV 2, 4.36–4.42 (2); SV 3, 3.09–3.29 (2). BR 1, 2.14 (1); BR 2, 1.7 (1); BR 3, 1.67 (1).

Genitalia ( Figs. 4A, E ). S VIII ( Fig. 4C ) with some short setae (30–65 μm) arising from the small pale pits (diameter 10–15 μm) on each side. Gonocoxite IX relative stout, laterally fused to the S IX, with 6–8, 7 setae. Gonocoxapodeme curved smoothly. Notum 100–120, 116 μm long, distinctly shorter than the rami, unsclerotized. Dorsomesal lobe ( Fig. 4D ) relative slender with inward-oriented setae, expanded medially; ventrolateral lobe ( Fig. 4D ) stout, with a few anteriomedian oriented long setae. Apodeme lobe ( Fig. 4D ) rod-like, with slightly expanded round apex, apparently bare. Labium bare. Three oval spermatheca, 75–90, 85 μm long at the long axis. Postgenital plate indistinct U-shaped. T IX with 10–15, 12 setae on each ovate protrusion.

Pupa (n=2, Figs. 5A–D )

Total length ( Fig. 5A ) 7.2–8.1 mm, abdomen length 5.3–6.1 mm. Coloration general yellow to light brown.

Cephalothorax. Cephalic tubercles and frontal setae absent. Median suture with heavy granulations. Basal ring oval, thoracic horn ( Fig. 5C ) 850–1000 μm long and 420–520 μm wide. Accessory respiration organ with four main tubular-shaped basal branches. Antepronotals with two median and two lateral setae, subequal in length, 120–150 μm long. Precorneal with two well-developed and one reduced seta, 100–140 μm for the two long and 60–75 μm for the latter. Prealars 80–110 μm long. Dc1 and Dc2 separated, gap between Dc1 and Dc2 110–200 μm; posterior two dorsocentrals grouped together, length of Dc 1–4 (in μm): 80–90; 50–60; 50–60; 35–50, the distance between Dc2 and Dc3 150–230 μm.

Abdomen. T I bare. T II–V with extensive spinulations, delimited into subquadrate to trapezoidal in general. Anterior band distinct only T II, median and posterior patches fused r. Spinulations on T VI–VII hour-glass to T-shaped, T VIII with paired anterolateral patches. Spinous pedes spurii B on segment II well developed, pedes spuria A on S IV–VIII. Segments VII–VIII with 4 lateral taeniae, the insertion of terminal taeniae extremely orolateral. Anal lobe 450–475, 465 μm high, 550–600, 555 μm wide, with 55–61 fringe setae, single row in basal 2/3, and multi-serial in the distal 1/3. Male genital sac distally bended inward ( Figs. 5B, D ), seldom extending the distal margin of anal lobe.

Larva (n = 2, Figs. 5E–I )

Larval exuviae ca. 7.5–8.8 mm. Head capsule 525–700 μm long, 400–500 μm wide, cephalic index 1.31–1.56.

Head ( Fig. 5E ) generally yellowish in color, apical mandible and mentum dark brown. Posterior occipital margin pale brown. Antenna ( Fig. 5I ) with 4 segments, each segment length (μm): 50–63; 17–24; 1.5–2.0; 3.0–4.0. AR 1.83–2.50. Basal segments 2.20–2.78 times as long as width, with one ring organ in the middle and two sense pits in basal 1/5 and apical 1/3 (just above the ring organ) respectively. Blade 22–28 μm long, extending beyond the third segment. SI serrate, with 5–6 branches. Labral lamella separately medially, each side with 18–24 teeth. Premandible simple, 90–100 μm long, brush absent. Mandible ( Fig. 5G ) 144–170 μm long, apical teeth 35–40 μm long, clearly longer than the combined width of three inner teeth. Seta subdentalis small, 8–10 μm long, slightly extending the inner most teeth. Seta interna with 7–8 nearly simple branches, 40–65 μm long. Mentum ( Fig. 5H ) somewhat squat, 150–160 μm wide in basal, clearly larger than its height (100–115 μm). Median teeth with a shallow notch, pale brown in color, 45–50 μm wide, MR 0.30–0.33. Six pairs of lateral teeth uniformly decreasing in size from top to lateral. Ventromental plate ( Fig. 5F ) 16–20 μm wide in basal curved section, with 3–5 weak beard in the extremely oral corner. Two large genal setae 18–24 μm away from the outer margin of ventromental plate. Postmentum 260–300 μm long, distance between setae submenti 55–75 μm long.

Body. Procercus 85–100 μm long, with 8 anal setae, 550–720 μm long. One pair of small basal setae (one strong, one short) in subapex of procercus. Unequal two supraanal setae on each side, the longer 450–530 μm long, the shorter 280–320 μm long. Anal tubes seldom extending beyond the terminals of posterior parapods.

Distribution. China Tibet.

Remarks. The male adult of M. secundibetica sp. n. is unique among all previously described Monodiamesa species in the combination of few clypeal setae, smooth inner margin of superior volsella and expanded subapex of gonostylus. Though clypeal setae can be reduced in some Nearctic species ( Saether, 1973), its occurrence with the two latter characters have not been observed in any known species. The female adult is hard to separate from worldwide congeners since most females lack detailed description, but the widely separated eyes, plus some short setae arising from S VIII distinguish from other Eastern Palaearctic species. Immature stages can be separated tentatively from others following the diagnosis, however, there is no guarantee of reliability when more larvae and pupae are reported since these species show much similarity.

Figures

FIGURE 3. Monodiamesa secunditibetica sp. n., male. Photos: (A) hypopygium; (B) clypeus; (C) MVo; (D) basal median lobe. Illustration: (E) hypopygium, dorsal view; (F) hypopygium, ventral view. Scale bar: A–B, 100 μm; C–F, 50 μm.

FIGURE 4. Monodiamesa secunditibetica sp. n., female. Photos: (A) hypopygium, ventral view. Illustration: (B) antenna; (C) S VIII; (D) dorsomesal lobe, apodeme and ventrolateral lobe; (E) hypopygium, ventral view. Scale bar: A–B, 100 μm; C–E, 50 μm.

FIGURE 5. Monodiamesa secunditibetica sp. n., immatures. Photos: (A–B) pharate, P/M, lateral view, dorsal view; (C) pupa, thoracic horn; (D) pupa, anal lobe; (E) larva, head capsule, ventral view; (F) larva, ventromental plate. Illustration: (G) larva, mandible; (H) larva, mentum; (I) larva, antenna. Scale bar: A–B, 100 μm; C, 200 μm; D–F, 100 μm; G, 20 μm; H, 50 μm; I, 25 μm.