Skusella silingae Tang, 2018

Cranston, Peter S. & Tang, Hongqu, 2018, Skusella Freeman (Diptera: Chironomidae): new species, immature stages from Africa, Asia and Australia, and expanded distributions, Zootaxa 4450 (1), pp. 41-65 : 53-56

Skusella silingae Tang , sp. n.

urn:lsid:zoobank.org:act:urn:lsid:zoobank.org:act:BA763D8D-138B-4812-9487-6FC6B77AD89E

( Figs 2D–F , 6A )

Material examined. Holotype ♂, CHINA, Guangdong Province, Guangzhou City, Conghua District, Lyutian Town, Dongkeng Reservoir , 23°53.277'N 113°55.069'E, 9.ix.2015, light trap (H.Q. Tang) ( EJNU) . Paratypes, ♂, as holotype; Pe / ♂ (pharate male), as holotype except 3.v.2017 (S.L. Hu & H.Q. Tang) (both ANIC) . CHINA, 1♂, Zhejiang Province, Hangzhou City, Tianmu Mt. , unnamed reservoir, 30°20.02'N 119°26.25'E, 800m asl, 27.vii.2011 (X.L. Lin) ; 2♂, CHINA, Yunnan Province, Dehong Dai & Jingpo Autonomous Prefecture, Ruili City, Mengxiu Town, Daoba country, stream in Ruili Botanic Garden , 24°02'N 97°29'E, 31.x.2015 (J. Liu).

Excluded. THAILAND: 1L, Chalyaphum Prov. , Amphur Chum Pae, pond, 16°35'N 102°02'E, 3.v. 2004, 217 m asl, #L-660 (Vitheepradit); Pe, Kampaeng Phet Prov, Khlong Lan N.P., Nam Tok Klong Lan , 16°07'N 99°16'E, 8.iii.2002, #L272.

Description. Adult male (n = 6, 1 pharate). Similar to S. subvittata in colour except abdomen uniform. Legs yellow except dark brown apex of fore femur and complete fore tibia, and pale brown basal half mid and hind tibia.

B.l. 3.4–4.0 mm, W.l. 1.6–1.8 mm.

Fl1–12 470–510. Fl13 570–610, A.R. 1.20–1.25.

Temporals 9–12 uniserial, some long; Clyp 13–18. Palp 2–5: 30–40, 140–200, 120–170, 205–258.

Thorax with one distinct hump. L.aps 0–3. Dc 3–5 (small pits omitted), usually posterior pore still most posterior, accompanied by 2 tiny pits, Pa 2–3, Scts 6–8.

Wing. Plain. V.R. 1.10–1.14. Vein setation: R 15–21, R 1 10–19, R4+ 5 15–24, squamals 0–1.

Legs. LR1 2.26–2.41, LR2 0.67–0.69, LR3 0.85–0.95. BV1 1.51–1.56, BV2 3.20–3.37, BV3 2.34–2.44. SV1 1.18–1.21, SV2 3.24–3.38, SV3 2.44–2.68.

Hypopygium ( Fig. 2D–F ). Tergite IX with 2–4 median setae. Anal point slightly spatulate subapically. Superior volsella ( Fig. 2E ) ca. 50 µm, with 3–4 lateral setae, 2 inner setae widely separated (10–15 µm), arising from distinct tubercle, 1 outer seta nearly always present (at least one side). Median volsella ( Fig. 2F ) stem ca. 35 µm, with ca. 40 split setae.

Pupa (n = 1–2). Body length 4.95 mm. Exuviae pale grey with brown apophyses.

Cephalothorax. Cephalic tubercle low and weak. Frontal setae 50 µm, shorter than distance between setae. Thorax clearly rugose at scutal hump, otherwise smooth. Prealar tubercle seemingly absent, area damaged in dissection of pharate adult.

Abdomen ( Fig. 6 A ). Similar to S. subvittata , with more extensive tergal spinulation. Pleural fringe slightly longer on IV–VII (90–100µm) than others (50–60 µm), on segment VIII slightly different to other segment, anterior ca. 75 µm, posterior ca. 150 µm. Hook row of 26–31 hooks, extending 27– 30% of segment width. Posterolateral corner of VIII (‘comb’) with 9–12 teeth of variable length. Anal lobe with 116–118 taeniae.

Larva. Material from Thailand may be conspecific to this species, but status will need molecular association.

Female unknown.

Etymology (Derivatio nominis). The species epithet honors the junior author’s mother, Siling Hu, who helped collect the pharate material during a camping field trip.

Comments. Skusella silingae resembles the type species, S. subvittata , in the known life stages. The wing is unmarked, the anal point is more spatulate distally with a rounded apex and the superior volsella has 3–4 lateral setae, of which 1 outer seta always is present, the apex tapering more abruptly ( Fig. 2E ). The pupa has a pleural fringe extending from the posterior of TIII to VIII, spinulation on tergites II–IV not extending laterally beyond adhesion marks, and with at least 25 hooklets on TII, row extending more than 1/4 of segment width.

Thai material is placed here as an atypical form of S. silingae since the pupal hook row has 31 hooklets, occupying ca. 30% of segment width, both measures greater than in the Chinese paratype.

The type locality is a relatively clean mountain reservoir. The water temperature ranges from 13.8°C to 25.1°C, dissolved oxygen 6.0– 7.2 mg /l, pH 6.7–7.8, total nitrogen 0.1–0.6 mg /l, total phosphorus 0.04–0.10 mg /l, and COD 2.4–15.2 mg /l.

Figures

FIGURE 2. Male Skusella, hypopygia. A–C S. freemani: A. (L side dorsal, R side schematic, ventral/internal); B, Superior volsella; C, Median volsella; D–F S. silingae sp. n.: D, Hypopygium (schematic, L side dorsal, R side ventral/internal); E, Superior volsella; F, Median volsella.

FIGURE 6. Skusella pupae, abdomen (dorsal). A, S. silingae sp. n.; B, S. sp. ‘Limuling’; C, S. sp. ‘Sanyatang’.