Polypedilum (Pentapedilum) convexum (Johannsen)

Oyewo, Emmanuel Adeoye & Saether, Ole A., 2008, Revision of Polypedilum (Pentapedilum) Kieffer and Ainuyusurika Sasa et Shirasaki (Diptera: Chironomidae), Zootaxa 1953, pp. 1-145 : 49-50

Polypedilum (Pentapedilum) convexum (Johannsen)

( Figs 13D–I)

Pentapedilum convexum Johannsen, 1932: 540 .

Polypedilum (Pentapedilum) convexum (Johannsen) ; Tokunaga (1964: 596), Cranston (1996: 258).

Material examined. INDONESIA: Sumatra, holotype male, 1928–9, A. Thienemann (Type No. B. M. 1937- 703, F21; BMNH) . CHINA: Tibet, Xiachayu County, Ba’antong , 2 males, 13.vi.1988 & 19.v.1988, light trap, C. Deng ( NU Nos. 05180, 05173) ; Guangxi Province, Jinxiuluo Town , 1 male, 7.vi.1990, sweep net, X. Wang ( NU No. 1562) .

Diagnostic characters. The male has a very broad anal point ( convexum group), similar to P. (Pe.) anale and P. (Pe.) kasumiense , with a distinct median furrow. P. (Pe.) convexum can be distinguished by the shape of the median furrow which is nearly parallel-sided medially and subapically, but broadens apically; that of P. (Pe.) anale and P. (Pe.) kasumiense are virtually V-shaped. Unlike P. (Pe.) anale and P. (Pe.) kasumiense , the abdominal segments are not banded. P. (Pe.) fanjingense and P. (Pe.) toyamadeeum have a similar anal point with furrow, but both have a very low antennal ratio (0.3–0.4) as opposed to 1.0– 1.4 in P. (Pe.) convexum .

The pupae of both P. (Pe.) convexum and P. (Pe.) kasumiense lack spinules on segments VII and VIII. However, P. (Pe.) convexum can be separated from P. (Pe.) kasumiense by having 2 spots of posterior shagreen on segments II – VI, as opposed to several rows of shagreen in P. (Pe.) kasumiense .

Male (n = 4, unless otherwise stated)

Total length 2.64–2.82 (2) mm. Wing length 1.37–1.89, 1.59 mm. Total length / wing length 1.59–1.68 (2). Wing length / length of profemur 2.12–2.36 (3). Thorax dark brown on postnotum, preepisternum and scutum; abdomen pale brown; femur, tibia and tarsi yellowish brown.

Head. AR 1.15–1.35, 1.22. Ultimate flagellomere 494–621, 542 µm long. Temporal setae 9–10 including 3 (1) inner verticals, 4 (1) outer verticals, and 2 (1) postorbitals. Clypeus with 18–24, 20 setae. Tentorium 114–117 (3) µm long, 5–7 (3) µm wide at posterior tentorial pit. Stipes 133 (1) µm long. Palpomere lengths (in µm): 32–61 (3); 44–56 (3); 96–105, 104; 114–127, 121; 189–209 (2). Fifth palpomere / third palpomere 1.80–2.16 (2).

Thorax. Acrostichals 11–18, 14; dorsocentrals 15–17, 16; prealars 4–5, 5. Scutellum with 6–8, 7.

Wing. Anal lobe moderately developed. VR 1.21–1.27, 1.24. Brachiolum with 1 seta, Sc 14–17 (3) setae; R with 20–28, 24; R 1 with 25–38, 30; R 4+5 with 46–60, 52; M with 8–16 (3); RM with 2 (3); M 1+2 with 40–81, 63; M with 27–39, 34; Cu with 12–39, 25; Cu 1 with 11–25, 17; PCu with 38–40 (3); An with 11 (1) setae. Cells m basal of RM, r 4+5, m 1+2, m 3+4, and cu plus an each with just more than 100 sparse macrotrichia. Squama with 5–8 (3) setae.

3+4

Legs. Scale on foretibia 28–34, 32 µm long; with 7–10, 9 µm long triangular spur. Spurs on midtibia 56– 68, 64 µm long; on hind tibia 63–84, 69 µm long. Comb on midtibia 13–23, 19 µm long; combs on hind tibia 21–30, 25 µm and 12–18, 17 µm long. Width at apex of foretibia 43–47, 44 µm; of midtibia 40–49, 46 µm; of hind tibia 47–52, 50 µm. Length and proportions of legs as in Table 12.

Hypopygium ( Fig. 13E). Tergite IX with 13–14 (2) setae, laterosternite IX with 1–4, 2 setae. Anal point ( Fig. 13D) with distinct median furrow; 52–75, 68 µm long; 40–68, 48 µm wide at base, 20–26, 24 µm at apex; median furrow 9–11, 10 µm long. Transverse sternapodeme 47–58, 52 µm long; phallapodeme 58–86, 65 µm long. Gonocoxite 133–158, 150 µm long. Superior volsella ( Figs 13G–I) 37–49, 44 µm long; base with microtrichia and 3–4 inner setae; projection needle-like, apex with 1 seta. Inferior volsella ( Fig. 13F) 78–96, 85 µm long; parallel-sided and slender, with 1 prominent apical seta. Gonostylus slender, 105–125, 119 µm long. HR 1.21–1.31, 1.26; HV 2.11–2.26 (2).

Pupa and larva. The immature stages are illustrated and partially redescribed by Cranston (1996).

Remarks. In the illustration of the male hypopygium in Johannsen (1932: 553) the projection of the superior volsella lacks a lateral seta. However, this seta is apparently present in all specimens examined thereafter by other authors. Johannsen also described the male abdomen as yellow with thin brown bands posteriorly; in subsequent publications it is either described as yellowish or pale brown, not banded.

Ecology and distribution. Indonesia, Caroline Islands, China, Japan, Bhutan, India, Palau, Federated States of Micronesia. According to Cranston (1996: 258) the species is acidophilic and may be found in phytotelmata.