Polypedilum (Probolum) bullum Zhang & Wang, 2004

Lei, Qi, Chen, Jinxian, Song, Chao, Qi, Xin & Zhang, Ruilei, 2020, Description of larva and female of Polypedilum (Probolum) bullum Zhang & Wang with DNA barcodes, Zootaxa 4890 (2), pp. 257-265 : 258-263

Polypedilum (Probolum) bullum Zhang & Wang, 2004

Polypedilum (Uresipedilum) bullum Zhang & Wang, 2004:7 ; Saether & Oyewo, 2008:3

Polypedilum (Probolum) bullum Zhang & Wang, Saether et al., 2010:15

Material examined: Specimens used to extract genomic DNA, 1 larva, China, Tibet Autonomous Region, Lhasa City, Damshung County, Yangbajin Town , 4396m, 30.14709°, 90.54750°, 23.VII.2014, R. Zhang , hand net. 2 larvae and 1 male, China, Tibet Autonomous Region, Nyingchi City , the Second Bridge , 2967m, 29.62573°, 94.37047°, 8.VII.2014, R. Zhang. 1 male, China, Tibet Autonomous Region, Bomi County , 2800m, 29.85555°, 95.77555°, 10.VII.2014, light trap, R. Zhang. 1 male, China, Tibet Autonomous Region, Lhasa City , Chushur , County , Chabala Village , 3603m, 29.38313°, 90.83390°. 1 female, China, Tibet Autonomous Region, Nyingchi City , Nyingchi Town , Nyang Qu , 2967m, 29.60527°, 94.40643°, 8.VII.2014, light trap, R. Zhang .

Additional Material examined: P. (Pro.) bullum Holotype: male (BDN. 13415) China, Sichuan Province, Xiangchen County, Shuoqu River, 2700m, 12.VI.1996; light trap, X. Wang. 10 males as holotype. 2 males, China, Sichuan Province, Yajiang County , Sandaoqiao, 2460m, 9. VI. 1996, light trap, X. Wang. 1 male: China, Sichuan Province, Batang County , Zhubalong Township , 2500m, light trap, R. Zhang .

Diagnostic characters. The wing marking pattern and shape of superior volsella will separate the male imago from other P. ( Probolum ) species. Ventrolateral lobe strongly developed, densely setose with apical setae and partially covered by dorsomesal lobe and wing marking pattern can differ the female imago from other P. ( Probolum ) species. The larva is distinguished within Probolum by the combination of following characters: mentum with 16 teeth, teeth even in height and color, mandible with 1 apical, 1 dorsal and 3 distinct inner teeth; pecten epipharyngis consisting of 3 platelets and each part with 3 blunt teeth, labral SI broadly lanceolate with fine filaments on each side of apical 1/2, labral SII palmate, with filamentous branches on apical margin.

Male imago (n =10). Total length 3.15–4.05, 3.62 mm. Wing length 2.35–2.75, 2.59 mm. Total length/wing length1.28–1.63, 1.40. Wing length/length of profemur 2.51–2.72, 2.62.

Colouration. Head brown. Thorax brown with darker vittae and postnotum. Abdominal segments and legs uniformly brown. Wing light brown with dark spots, one spot just distal of r-m cross vein, one spot on the middle of cell r 4+5, one stripe spot on anal vein, one weak cloudy spot distal to fork of M 3+4 and Cu 1, weak cloudy spot at distal apex of wing.

Head. AR 1.12–1.25, 1.19. Temporal setae 12–16, 14; including 3–4, 3 inner verticals; 4–6, 5 outer verticals and 4–8, 6 postorbitals. Clypeus with 14–27, 17 setae. Tentorium 143–170, 156 μm long, 35–50, 43 μm wide. Palpomere lengths (in μm): 33–55, 43; 33–53, 46; 145–177, 158, 123–172, 150; 200–294, 261.

Wing ( Fig. 1A ). VR 1.08–1.18, 1.13. R with 21–27, 24 setae; R 1 with 14–23, 18; R 4+5 with 27–48, 37 setae. Squama with 14–21, 17 setae.

Thorax. Dorsocentrals 13–27, 20; acrostichals 15–18, 16; prealars 4–8, 5. Scutellum with 17–29, 23 setae.

Legs. Terminal scale ( Fig. 1B ) of front tibia pointed, 52–65, 57 µm long. Spur on median tibia 42–50, 46 um long including 23–33, 28 µm long comb, un-spurred comb 20–28, 24 µm long. Spur on posterior tibia 47–58, 52 μm long including 25–33, 29 μm long comb, un-spurred comb 23–33, 27 μm long. Width at apex of front tibia 53–63, 58 μm, of middle tibia 58–65, 62 μm, of hind tibia 55–78, 68 μm. Lengths (in μm) and proportions of legs of male imago as in Table 2.

Hypopygium ( Figs. 1 C–H). Anal tergite bands fused basal to median anal tergite setae ( Fig. 1C ). Anal tergite with 6–10, 8 median setae, laterosternite with 3–6, 5 setae. Anal point 80–98, 91 μm long, slender and parallel-sided for entire length Phallapodeme 90–130, 120 μm long; transverse sternapodeme 50–83, 64 μm long. Gonocoxite 175–205, 193 μm long. Base of superior volsella with a prominent process bearing 1–3 inner setae in the inner margin, distal extension variably curved with 1–3 lateral setae ( Figs. 1 D–H). Inferior volsella 90–130, 110 μm long tapered apically, with 11–15 oral setae and an apical seta. Gonostylus 120–150, 134 μm long, outer margin convex, widest in the middle. HR 1.33–1.60, 1.44. HV 2.32–2.93, 2.69.

Female (n = 1). Total length 3.0 mm. Wing length 2.48 mm. Total length/wing length 1.21. Wing length/length of profemur 2.88.

Colouration. Head brown. Thorax brown with darker vittae and postnotum. Abdominal segments and legs brown. Wing light brown with weak marking as male ( Fig. 2A ).

Head. AR 0.42. Temporal setae 13, including 4 inner verticals; 4 outer verticals and 5 postorbitals. Clypeus with 18 setae. Tentorium 130 μm long, 24 μm wide. Stipes 160 μm long. Palpomere lengths (in μm): 40, 68, 130, 150, 260. Third palpomere with 3 sensilla clavata in small pit, longest 15 μm long.

Thorax. Acrostichals 12, dorsocentrals 18, prealars 5. Suctellars 23, biserial.

Wing. VR 1.17. Brachiolum with 1 seta, R with 22, R 1 with 19, R 4+5 with 46 setae. Squama with 14 setae.

Legs. Terminal scale on fore tibia 53 μm long. Spur of mid tibia 40 μm long including 13 μm long comb, unspurred comb 18 μm long. Spur on hind tibia 45 μm long including 15 μm long comb, un-spurred comb 23 μm long. Width at apex of fore tibia 53 μm, of mid tibia 58 μm, of hind tibia 65 μm. Length and proportions of leg segments as in Table 3.

Genitalia ( Figs. 2 B–C). Gonocoxapodeme curved, 145 μm long. Gonocoxite IX with 5 setae. Tergite IX with 37 setae. Cercus 113 μm long, 85 μm wide. Seminal capsule ovoid and pellucid, 85 μm long. Notum 168 μm long. Dorsomesal lobe 83 μm long from base of vagina to apex, 73 μm wide near apex. Dorsomesal lobe strongly devel-oped, densely setose with apical setae curved mesad. Ventrolateral lobe 35 μm long, 75 μm wide, densely setose with apical setae directed more oralad than mesad. Ventrolateral lobe partially covered by dorsomesal lobe.

Larva (n=3). Total length not measurable. Head capsule (Fig. 3A) 0.38–0.40 mm long, 0.35–0.36 mm wide. Postmentum 147–165 μm long.

Colouration. Head capsule brown with dark brown mental teeth and mandible teeth. Postoccipital margin black.

Head. AR 1.05–1.12. Antenna as in figure 3B. Antennal segment lengths (in μm): 50–55, 18–20, 10–12, 12–13, 5–5. Basal antennal segment 20–23 μm wide, ring organ about 15–23 μm from base, blade 33–35 μm long, blade extending beyond base of fourth segment. Labral SI (Fig. 3C) broadly lanceolate, with fine filaments on each side of apical 1/2. Labral SII palmate (Fig. 3D) with filamentous branches on apical margin. Pecten epipharyngis as in figure 3E, consisting of 3 platelets, each with 3 blunt teeth. Premandible (Fig. 3E) 65–73 μm long, with 2 apical teeth and 1 inner tooth and brush present. Mandible (Fig. 3F) 115–125 μm long, with 1 apical, 1 dorsal and 3 distinct inner teeth; molar area yellow brown; medial margin with 2 sharply pointed serrations; seta subdentalis 23–27 μm long, beyond second inner tooth. Mentum (Fig. 3G) 105–115 μm wide, with 16 blunt teeth, last lateral tooth very small; medial 6 teeth larger than remaining teeth, fifth lateral tooth lower than neighboring teeth. Ventromental plate 130–133 μm wide, 53–58 μm high, with about 35–40 striae, distance between ventromental plates 43–48 μm, ven-tromentum wider than mentum, with the medially-directed pointed apex. Distance between setae submenti 98–105 μm.

Abdomen. Posterior parapods (Fig. 3H) 230–250 μm long, 110–120 μm wide, with 14–16 yellow apical claws. Procercus (Fig. 3I) weak and slender, with about 7–10 anal setae up to 430–460 μm long. Supraanal setae 300–325 μm long. Ratio of supra anal setae/anal setae 0.70–0.71. Anal tubules 120–130 μm wide.

Larval habitat and distribution: Polypedilum (Pro.) bullum Zhang & Wang is found in Sichuan Province and Tibet Autonomous Region, China. So far, this species has been recorded above an elevation of 2,460 m. The larva lives in fast flowing, wide, shallow rivers with sand or mud in the bottom.

Remarks: P. (Pro.) bullum Zhang & Wang is clearly distinguished from P. (Pro.) marcondesi Pinho & Mendes, 2010 in morphological characteristics of the male, female and larva. Male imago of P. (Pro.) bullum Zhang & Wang morphologically resembles P. (s. str.) laetum (Meigen) , Polypedilum (s. str.) castornama Maschwitz and P. (s. str.) tuberculum Maschwitz in having dark color body, weak or distinct wing marking, base of superior volsella with inner lobe/tubercle, slender anal point, short and strong gonostylus. The significant characters to differ them are the shape of inner lobe/tubercle of superior volsella and wing markings as listed in Table 4. Larva of P. (Pro.) bullum Zhang & Wang is very close to P. (s. str.) tuberculum Maschwitz and P. (s. str.) laetum (Meigen) . They share the following characters: mentum with 16 teeth; teeth even in height and color; mandible with 1 apical, 1 dorsal and 3 distinct inner tooth; pecten epipharyngis consisting of 3 platelets, mid part with 3 teeth. Labral SI has fine filaments on each side of apical 1/2 and labral SII is palmate in P. (Pro.) bullum Zhang & Wang ; correspondingly, labral SI has fine filaments on each side of apical 1/3 and labral SII is more slender in P. (s. str.) tuberculum Maschwitz. There is no other significant feature to distinguish the larva of P. (Pro.) bullum Zhang & Wang with P. (s. str.) tuberculum Maschwitz. The larval differences between P. (s. str.) tuberculum Maschwitz and P. (s. str.) laetum (Meigen) refer to Maschwitz & Cook (2000).

In diagnosing Probolum , Andersen and Saether (2010) described the character of superior volsella with an inner lobe at base carrying 1–6 (10?) setae and a typical Uresipedilum -like apicomedian projection directed inwards. Polypedilum (Pro.) bullum Zhang & Wang had been firstly assigned in the subgenus Uresipedilum by having the superior volsella with an apicomedian projection in holotype. However, based on some new additional specimens, we found that the projection of superior volsella bends variably ( Figs. 1 D–H) in P. (Pro.) bullum . Andersen & Saether (2010) regarded ‘mentum with median teeth only slightly higher than first lateral pair’ as a significant diagnostic character in the subgenus Probolum . But mental teeth are in even height in P. (Pro.) bullum Zhang & Wang. The diagnosis of Probolum giving by Andersen & Saether (2010) should be expanded. Andersen & Saether (2010) stated that the pupae of Probolum were not separable from those of Polypedilum s. str., Pentapedilum and Uresipedilum . As stated above, distinct diagnostic characters for all stages in the subgenus Probolum are unavailable at present. We concur with Yamamoto & Yamamoto (2015) that the subgenus Probolum should be restricted to the species with an inner lobe in the superior volsella until adequate pupal and larval information are available, then P. (s. str.) laetum Meigen , P. (s. str.) castornama Maschwitz and P. (s. str.) tuberculum Maschwitz should be included in subgenus Probolum , but the type material need to be checked in the future.

FIGSURES 3A–G. P. (Pro.) bullum Zhang & Wang , larva. A, head capsule. B, antenna and mandible. C, SI seta. D, SII seta. E, premandible. F, mandible. G, mentum and ventromental plates. H, anal segments. I, procercus.

Figures

FIGURES 1A–H. P. (Pro.) bullum Zhang & Wang, male. A, wing. B, terminal scale of front tibia. C, hypopygium. D–H, superior volsella.

FIGURES 2A–C. P. (Pro.) bullum Zhang & Wang, female. A, wing. B, hypopygium. C, dorsmesal lobe and ventrolateral lobe.