Polypedilum (Pentapedilum) sordens (van der Wulp)

Oyewo, Emmanuel Adeoye & Saether, Ole A., 2008, Revision of Polypedilum (Pentapedilum) Kieffer and Ainuyusurika Sasa et Shirasaki (Diptera: Chironomidae), Zootaxa 1953, pp. 1-145 : 99-104

Polypedilum (Pentapedilum) sordens (van der Wulp)

( Figs 33–34)

Tanytarsus sordens van der Wulp, 1874: 141 .

Tanytarsus fulvescens Johannsen, 1905: 293 , syn. n.

Tanytarsus sordens van der Wulp ; Goetghebuer (1921: 109).

Pentapedilum (Pentapedilum) sordens van der Wulp ; Edwards (1929: 376) [generic position].

Pentapedilum (Pentapedilum) fulvescens Johannsen, 1934: 352 [generic position].

Polypedilum (Pentapedilum) sordens van der Wulp ; Townes (1945: 61), Maschwitz and Cook (2000: 28, 32), Epler (2001: 128, 134).

Material examined. BELGIUM: Genval , 2 males [marked syntype but collected in 1917], 28.vi.1917, 10. vii.1917, A. Tonnoir ( IRSN No. 893) ; Postel , 5 males, vii.1922, G. Severin ( IRSN) ; Destelbergen , 1 male, 18.xi.1919, G. Severin ( IRSN) . GERMANY: West Parle, Munich , 2 males, B. Peters ( ZSM Nos. 4.1, 4.2) ; Ost-Holstein, Unterer Schierenseebach , 1 male, 02.viii.1986, U. Holm ( ZSM No. 196) ; Ost-Holstein, Trammersee , 1 male with associated pupae, 21.viii.1951, I. Müller-Liebenau ( ZSM) ; Ober-Bayern, Weβlinger See , 3 pupae, 01.viii.1990, N. Reiff ( ZSM) ; Bodensee-Gebiet , 4 pupae, 27.v.1962, F. Reiss ( ZSM) ; unknown locality, 3 pupae A. Thienemann ( ZSM 173 ) . NORWAY: Hordaland, Øygarden, Alvøy, Dalsvatn , 1 male, 05.vi.1987, T. Andersen ( ZMBN) . THE NETHERLANDS: Friesland, Scheeme , 3 larvae, 28.vi.76, T. Claassen ( ZSM) . USA: Minnesota, Washington County, Stillwater , 1 male, 9.vi.1969, D. E. Maschwitz ( UMSP) ; Minnesota, Becker County, Hubble Pond , 1 male, 16.viii.1982, light trap, N. Kirsch ( UMSP No. 8) ; Minnesota, Clear water County, Sucker Brook , 1 female with associated larva and pupa, 03.viii.1969, D. E. Maschwitz ( UMSP No. R-67) ; Minnesota, Shoreview , 1 female with associated larva and pupa, 18.vii.1969, D. E. Maschwitz ( UMSP No. R-61) ; Montana, Beaver Creek Park, 1 male, 24.vi.1968, light trap, R. A. Hellenthal ( UMSP) ; Ohio, Fern Lake Bog, Geauga , 1 male, 1 female, 2 pupae, 2 larvae, 02.viii.1992, 12.vi.1992, M. J. Bolton (Nos. 34, 35, 36, 37) . MONGOLIA: Wolfssprung, Conocharajch , 1 male, 05.viii.1977, M. Stubbe ( ZSM) ; Somon, Dörgön, Aimak choud, 1 male, 17.viii.1980, M. Stubbe ( ZSM) .

Diagnostic characters. Among species with densely haired wing membrane, abdomen with broad dark bands and foretibial scale normally with spur, only P. (Pe.) sordens has the base of the superior volsella bare and the inferior volsella parallel-sided. The female can be distinguished by the peculiar shape of the lobes of gonapophysis VIII, especially the ventrolateral lobe which is nearly S-shaped and the dorsomesal lobe. The pupa has shagreen pattern on tergites IV and V in 4 separate patches. The larva has the third and fourth antennal segments subequal in length; and very broad and wide ventromental plates, with the width nearly 5 times the distance between the ventromental plates.

Male (n = 13–19, unless otherwise stated)

Total length 3.48–5.13, 4.14 (10) mm. Wing length 2.10–3.02, 2.49 mm. Total length / wing length 1.59– 1.85, 1.69 (8). Wing length / length of profemur 2.29–2.92, 2.50. Thorax brown to dark brown; abdominal segments with broad dark brown bands ( Fig. 40E); femur, tibia and tarsi brown.

Head ( Fig. 33A). AR 1.78–2.03, 1.94. Ultimate flagellomere 729–959, 870 µm long. Temporal setae 9–16 including 3–9, 5 inner verticals; 3–6, 4 outer verticals; and 1–4, 3 postorbitals. Clypeus with 22–40, 30 setae. Tentorium 121–202, 166 µm long; 6–17, 9 µm wide at posterior tentorial pit. Stipes 121–238, 171 µm long. Palpomere lengths (in µm): 32–52, 40; 57–80, 65; 169–212, 191 (11); 155–231, 171 (11); 249–307, 237 (7). Fifth palpomere / third palpomere 1.41–1.63, 1.49 (7). Third palpomere with 3 sensilla clavata.

Thorax ( Fig. 33B). Acrostichals 8–25, 16; dorsocentrals 20–55, 36; prealars 7–13, 9. Scutellum with 8– 25, 16 setae.

Wing. Anal lobe moderately developed. VR 1.03–1.13, 1.08. Brachiolum with 3–7, 6 setae; R with 48–92, 74; R 1 with 48–112, 75; R 4+5 with 92–164, 126; Sc with 27–88, 61; RM with 2–5, 3; M with 8–32, 24; M 1+2 with 55–130, 76; M 3+4 with 43–122, 77; Cu with 72–120, 79; Cu 1 with 25–50, 36; PCu with 73–115, 95; An with 28–61, 49 (11) setae. Cells r 4+5, m 1+2, m 3+4, cell m basal of RM, cu plus an each with dense macrotrichia. Squama with 8–18, 11 setae.

Legs. Scale on foretibia ( Fig. 33C) 38–71, 58 µm long, with minute up to 19 µm long apical or subapical spur. Spurs on midtibia 40–80, 62 µm long; on hind tibia 43–82, 66 µm long. Comb on midtibia 15–29, 21 µm long; combs on hind tibia 24–34, 29 µm and 12–28, 20 µm long. Width at apex of foretibia 48–71, 60 µm; of midtibia 61–77, 67 µm; of hind tibia 43–82, 73 µm. Length and proportions of legs as in Table 40.

Hypopygium ( Fig. 33G). Tergite IX with 10–22, 15 median setae; laterosternite IX with 2–3, 2 setae. Anal point 71–137, 94 µm long, 8–38, 17 wide at base, gradually tapering to nearly parallel-sided towards 8–18, 12 µm wide apex. Transverse sternapodeme 62–133, 93 µm long; phallapodeme 88–140, 110 µm long. Gonocoxite 193–267, 230 µm long. Superior volsella (33J–G) 73–112, 91 µm long; base bare with 3–5, 4 inner setae; projection with 0–1 lateral setae. Inferior volsella (33H, I) 124–189, 160 µm long; parallel-sided, with prominent apical seta. Gonostylus broad, 174–224, 196 µm long. HR 0.90–1.35, 1.21; HV 1.85–2.59, 2.16 (9).

Female (n = 1–3)

Total length not measurable. Wing length 1.94–2.39 mm. Wing length / length of profemur 2.43–2.66. Thorax dark brown at postnotum, antepronotum, preepisternum, and scutum or almost completely brown; abdominal segments with or without broad dark bands; femur, tibia and tarsi brown.

Head. AR 0.36–0.49. Length of flagellomeres (in µm): 132–142, 86–90, 86–102, 52–71, 126–190. Temporal setae 12–14, including 3–5 inner verticals, 4–5 outer verticals, and 2–6 postorbitals. Clypeus with 33–39 setae. Tentorium 133–157 µm long, 8–10 µm wide at sieve pore, 5–6 µm wide at posterior tentorial pit. Stipes 124–159 µm long. Palpomere lengths (in µm): 31–42, 45–51, 142–157, 145–147, 226–261. Fifth palpomere / third palpomere 1.44–1.76.

Thorax. Acrostichals 14–18, dorsocentrals 28–39, prealars 6–12. Scutellum with 12–19 setae.

Wing. Anal lobe reduced. VR 1.10–1.18. Brachiolum with 1–5 setae, R with 49–66, R 1 with 63–80, R 4+5 with 99–118, Sc with 4–62, RM with 2–3, M with 20–29, PCu with 71 (1) setae. Setae on veins M 1+2, M 3+4, Cu, Cu 1, and An obscure because wing membrane densely covered with macrotrichia. Squama with 7–18 setae.

Legs. Scale on foretibia 38–57 µm long, with apical or subapical 9 µm long spur. Spurs on midtibia 47–60 µm long, on hind tibia 51–70 µm long. Comb on midtibia 17–22 µm long, combs on hind tibia 20–26 µm and 14–24 µm long. Width at apex of foretibia 49–60 µm, of midtibia 55–60 µm, of hind tibia 63–77 µm. Length and proportions of legs as in Table 41.

Genitalia ( Fig. 33P). Gonocoxite IX with 3–6 setae, tergite IX with 13–42 setae, segment X with 8–9 setae. Cercus 131–147 µm long, 2–4 µm wide at apex. Seminal capsule nearly spherical, 60–64 µm long, 40– 58 µm wide; neck sclerotized, 11–15 µm long. Notum 144–174 µm long. Dorsomesal lobe ( Fig. 33S) 76–100 µm long, 22–44 µm wide, ventrolateral lobe ( Fig. 33Q) nearly S-shaped with straight brushes; apodeme lobe ( Fig. 33 R) S-shaped. Postgenital plate triangular.

Pupa (n = 13, unless otherwise stated)

Total length 4.07–7.02, 5.90 (9) mm. Frontal seta, cephalothorax, margins of segments, and caudolateral spur brown.

Cephalothorax ( Figs 34A–B). Cephalic tubercules absent. Frontal setae 39–64 (3) µm long. Prealar tubercle apparently absent. Wing sheath 1.26–2.12, 1.79 mm long.

Abdomen ( Figs 34C–E). Tergite I bare, tergites II – VI each with strong, prominent anterior row of spines; tergites II – III with few weak and sparse or occasionally extensive medial shagreen; tergites IV – V with two patches of extensive medial and two distinct patches of posterior shagreen, tergite VII with only two patches of posterior shagreen. Tergite VII with paired anterolateral spots of spinules, tergite VIII bare. Tergites VII – VIII without shagreen. Conjunctive IV / V with multiserial band of anterior pointed spinules. Tergite II with single row of 52–74, 60 (7) caudal hooks. Pedes spurii A present on segment IV. Pedes spurii B weakly developed on segment II. Caudolateral spur ( Figs 34F, G) 105–176, 134 µm long; with 1 strong apical tooth, 2–4 lateral teeth and several accessory points. Segments I– IV without L taeniae, V – VI each with 3 taeniae; VII – VIII each with 4 taeniae. Anal lobe fringe with 39–53, 45 taeniae. Length of genital sac overreach 243–488, 329 µm.

Larva (n = 6–8, unless otherwise stated)

Total length not measurable. Postmentum 2.09–2.45, 221 (5) µm long. Head segments brown with postoccipital margin, teeth of mentum and mandible dark brown. Frontoclypeal apotome not discernible.

Head. AR 1.16–1.36, 1.25 (4). Antennal ( Fig. 34H) segment lengths (in µm) 58–82, 72; 20–30, 25; 10– 18, 14; 11–18, 14; 4–5, 5 (5) ( Fig. 42E). Basal antennal segment 14–21, 17 µm wide, ring organs and sensory pits not discernible; blade 51–95, 61 µm (5) long, shorter than flagellum. Pecten epipharyngis ( Fig. 34L) consisting of 3 platelets, each with 4–5 unequal teeth. Premandible ( Fig. 34J) 97–117, 103 µm long, bifid with prominent premandibular brush. Mandible ( Fig. 34I) 157–176, 164 µm long with 1 apical and 3 inner teeth; seta subdentalis slender and well developed, distally straight; seta interna prominent; pecten mandibularis prominent and pointing towards teeth. Mentum ( Fig. 34K) 129–147, 138 µm wide, with 8 pairs of teeth. Median tooth 19–30, 25 µm wide, second lateral slightly shorter than median, first lateral tooth subequal to third, fourth to sixth decrease progressively to minute seventh. Ventromental plate 151–179, 161 µm wide; distance between plates 29–43, 35 µm; median apices of plates pointing towards each other. Ratio of ventromental plate / mentum 1.11–1.23, 1.20.

Abdomen. Procercus 7–18, 11 (5) µm high, 14–38, 24 (5) µm wide; with 6–8 478–603, 536 (5) µm long anal setae. Supraanal setae 340–382 (2) µm long. Posterior parapods 155–307, 254 µm long. Anal tubules 115–268, 170 (3) µm long; 48–53, 51 (3) µm wide at base; 38–42, 39 (3) µm wide at middle and 11–14, 13 (3) µm wide at apex.

Remarks. Most specimens bear an apical or subapical spur on the foretibia. However, a few specimens lack spur, but have a pointed scale. Two specimens from Mongolia lack a lateral seta on the projection of the superior volsella, confirming the description by Townes (1945). Some specimens from China have also been reported to lack the lateral seta on the projection of the superior volsella, and when present, the positions may vary ( Zhang & Wang 2005). The projection of the superior volsella is slightly curved at apex and may be similar to P. (Pentapedilum) nubens and P. (Pentapedilum) scirpicola , but the species can be distinguished by the broad gonostylus and the banded abdominal segments.

The larva of P. (Pe.) sordens and Asheum beckae (Sublette) are very similar. However, the antennal blade is shorter than the flagellum in P. (Pe.) sordens , longer in A. beckae . In both species the median tooth is slightly taller than the first lateral tooth, nearly of the same size as second lateral, followed by progressively shorter lateral teeth and a minute seventh tooth; but the first lateral tooth appear slightly lower in P. (Pe.) sordens than in A. beckae . The distance between the ventromental plates appears to be larger in A. beckae and the plates are more slender and posteriorly pointed in P. (Pe.) sordens . The larva of A. beckae , however, has not been examined and the differences mentioned may not stand closer scrutiny.

Distribution. Widespread in the Palaearctic region, China, Japan and USA ( Oliver et al. 1990; Sasa & Kikuchi 1995; Saether & Spies 2004).