Polypedilum (Polypedilum) isigabeceum Sasa et Suzuki, 2000

Yamamoto, Nao & Yamamoto, Masaru, 2016, The taxonomic implication of frontal tubercles in Polypedilum subgenera diagnoses, with re-description of Polypedilum isigabeceum Sasa & Suzuki (Diptera, Chironomidae), Zootaxa 4193 (1), pp. 189-194 : 190-191

Polypedilum (Polypedilum) isigabeceum Sasa et Suzuki, 2000

( Figs. 1–9 )

Polypedilum (Polypedilum) isigabeceum Sasa et Suzuki, 2000: 5 .

Material examined. Type material: Holotype male, Japan, Ryukyus, Okinawa Pref., Yaeyama Isls., Ishigaki Is., Nakura River, 30. VI. 1999, H. Suzuki. [Holotype: male, No. 385:01]; Additional material: 3 males, as previous except Shirahama, Iriomote Is., 27. IX. 2007, light trap, N. Yamamoto, T. Hirowatari, G.H. Huang and S. Kobayashi.

Type locality. Japan, Ryukyus, Okinawa Pref., Yaeyama Isls., Ishigaki Is., Nakura River .

Diagnosis. The species resembles P. (P.) crassityla Kawai, Inoue et Imabayashi , but distinguish from the latter by having the yellowish scutum with three distinct blackish colour bands and the wing without dark markings.

Male (n = 4). Total length 2.5–2.7 mm. Wing 1.2–1.4 mm long, 0.3–0.4 mm wide; wing length/wing width 3.50–4.13.

Colouration. Head including vertex, frons, antennal pedicel and antennal flagellum brown; palpomeres pale brown; clypeus dark brown; labella yellowish brown. Thorax with antepronotum pale brown; scutellum, postnotum, anepisternum I and epimeron I brown; dorsolateral line and halter yellowish white; scutum except dorsolateral line, preepisternum II and posterior 1/2 of epimeron II yellowish brown; anteanepisternum II, medioanepisternum II, anterior 1/2 of epimeron II blackish brown. Legs yellowish brown in ground colour; basal 1/ 3 of fore femora dark brown; fore tarsomere 3-5 pale brown. Abdomen predominately blackish brown.

Head ( Fig. 1–2 ). Frontal tubercle 5–10 µm long. 8–10 µm wide. Vertex with 8 temporal setae. AR 1.64–1.70. Prementum with 1 seta. Palpomere lengths (in µm): 20, 28, 83, 90, 115; with 1, 6, 12, 11, 8 setae, respectively; third palpomere with 1 sensillum clavatum. Clypeus with 12 setae.

Thorax ( Fig. 3 ). Lateral antepronotals absent. Dorsocentrals 7, uniserial; acrostichals 5, biserial; prealars 3, uniserial. Scutellum with 3 setae, uniserial.

Wing ( Fig. 4 ). Anal lobe moderately developed. VR 1.19–1.30. R2+3 nearly parallel with R1 and ended at basal 1/6 between apices of R1 and R4+5. R, R1 and apical 1/2 of R4+5 with 12, 6, 9 setae, respectively. Brachiolum with 2 median setae. Squama with 4 setae.

Legs ( Fig. 5 ). Scale of fore tibia triangular, with smoothly rounded apex, without spur or terminal extension, with a long seta. Fore, mid and hind coxae with 5, 2, 3 marginal setae, respectively; fore, mid and hind trochanters with 7, 5, 6 marginal setae, respectively; spur of mid tibia 33–40, 36 µm long, hind tibia 38–48, 43 µm long.

Hypopygium ( Figs. 6–9 ). Tergite IX with 8–9 median setae. Anal point long, slender, parallel-sided, with pointed apex ( Fig. 7 ). Superior volsella long, nearly straight, gently tapering to apex, with dorsolateral seta situated on its apical 1/2, base covered microtrichia and 2–3 inner setae ( Fig. 8 ). Inferior volsella long, moderately developed, parallel-sided, boots-like shape apex, reaching level of the anal point apex, with setae on dorsoapical portion, and a long seta extending posteriorly on ventroapical portion ( Fig. 9 ). Phallapodeme 58–63, 60 µm long. Sternapodeme narrow; transverse stenapodome 15–20, 18 µm long. Gonocoxite with 4 uniserially arranged setae on inner margin. Gonostylus long, moderately developed, with one short apical seta and 5–6 long setae on inner margin of apical 5/7.

Distribution. Japan (Yaeyama Islands: Ishigaki Island and Iriomote Island)

*P1–3: front-, mid-, hind-legs. Fe: femur. Ti: tibia. Ta1-5: tasomeres 1–5. LR: leg ratio. BV: combined length of femur, tibia and basitarsus divided by combined length of tarsomeres 2–5. SV: ratio of femur plus tibia to metatarsus.

Figures

FIGURE 1. Holotype photograph of a male head structure of Polypedilum (Polypedilum) isigabeceum.

FIGURES 2 – 9. Adult male of Polypedilum (Polypedilum) isigabeceum. 2: head; 3: thorax, lateral view; 4: wing; 5: scale of foretibia; 6: genitalia, dorsal view; 7: anal point, lateral view; 8: superior volsella, dorsal view; 9 inferior volsella, lateral view.