Nilothauma angustum, Qi, Xin, Tang, Hongqu & Wang, Xinhua, 2016

Qi, Xin, Tang, Hongqu & Wang, Xinhua, 2016, Notes on Nilothauma Kieffer from Oriental China, with descriptions of three new species (Diptera, Chironomidae), ZooKeys 574, pp. 143-159 : 144-145

Taxon classification Animalia Diptera Chironomidae

Nilothauma angustum sp. n. Figs 1-11

Type material.

Holotype: male (EJNU), CHINA: Yunnan, Ximeng City, Mengsuo Lake, 22°38.689'N, 99°35.631'E, Alt. 1090m, 27.viii.2014, Tang HQ, light trap. Paratype: 1 male (LTZU), as holotype.

Diagnosis.

The adult male of Nilothauma angustum sp. n. can be distinguished from all other known species of the genus by the following combination of characters: wing with four partially connected dark markings; anterior T IX projection extensively microtrichiose, divided into two lobes, each with apical simple setae forming a fan-like structure; posterior T IX projection extensively microtrichiose, nearly parallel-sided, setose, with long anterolateral arms; anal point broadly lanceolate, microtrichiose along the median ridge and the apical margin; median volsella with microtrichia and two apical setae; gonostylus peaked apically.

Etymology.

From the Latin angustus (narrow), referring to the male hypopygium with apically narrowed gonostylus.

Description.

Male imago (n = 2).

Total length 2.1−2.2 mm. Wing length 0.9−1.1 mm. Total length/wing length 2.1−2.2. Wing length/length of profemur 2.1−2.2.

Coloration. Generally yellow, thorax (Fig. 2) yellow except scutum, pre-episternum, scutellum and postnotum dark brown, abdomen yellowish brown. Wing with 4 partially connected dark markings (Fig. 1). Foreleg yellow with both ends of femur, apex of tibia, apical 1/3 of ta1, and ta2−5 brown; mid leg with sub-apex of femur and sub-base of tibia brown; hind leg with sub-apex of femur brown (Fig. 3).

Head. AR 0.18−0.20. Temporals 7−11, uniserial. Clypeus with 17−19 setae. Tentorium 80−108 μm long, 11−15 μm wide; stipes 50−65 μm long, 6−8 μm wide. Lengths of palpomeres 1−5 (in μm): 28−30, 25−30, 58−63, 85−105, 125−130. Palpomere 3 with 2 sensilla clavata; Pm5/Pm3 2.1−2.2.

Thorax (Fig. 2). Antepronotal lobe much reduced. Dorsocentrals 9−10, uniserial; acrostichals 7−9, biserial; prealars 2. Scutellum with 2 setae.

Wing (Fig. 1). VR 1.5−1.6. Brachiolum with 1 seta, R with 9−13 setae, R1 with 6−9 setae, R4+5 with 10−11 setae.

Legs (Fig. 3). Spur of fore tibia 63−65 μm long including 30−35 μm long scale (Fig. 4). Spur of mid tibia 20−25 μm long (Fig. 5) including 13−15 μm long comb. Spurs of hind tibia 18−25 μm and 28−30 μm long, respectively; comb 15−20 μm long (Fig. 6). Width at apex of fore tibia 28−30 μm, of mid tibia 33−35 μm, of hind tibia 30−34 μm. Lengths and proportions of legs in Table 1.

Hypopygium (Fig. 7). Tergite IX with 2 dorsal projections. Anterior projection (Fig. 8) microtrichiose, 60−63 μm long, 20−23 μm wide at base, split into 2 lobes; each 40−45 μm long, 10−12 μm wide at base, 5−6 μm wide at apex, with simple apical setae, together forming fan-like structure. Posterior projection (Fig. 9) extensively microtrichiose, 37−40 μm long, 35−40 μm wide at base, 17−20 μm wide at apex, nearly parallel-sided, apically rounded with 8 setae; long anterolateral arms present. Anal point (Fig. 10) broadly lanceolate, 30−35 μm long, 25−28 μm wide at base, 28−30 μm wide at middle, with microtrichia along median ridge and apical margin. Posterior margin of tergite IX (Fig. 11) with 8−10 setae located to each side of anal point. Laterosternite IX with 3 setae. Phallapodeme 28−30 μm long. Transverse sternapodeme rounded medially without median elongation. Gonocoxite 78−80 m long. Superior volsella 30−35 μm long, slender, club-shaped with 4 apical setae, without microtrichia. Median volsella 8−10 μm long, with 2 apical setae and microtrichia. Inferior volsella 53−58 μm long, pointed apically, with microtrichia and 6−7 apically cleft setae. Gonostylus 88−90 μm long, apically narrowed and peaked, with row of 4−5 split distal-median setae. HR 0.86−0.89, HV 2.3−2.5.

Female imago, pupa and larva. Unknown.

Remarks.

The male hypopygium is similar to those of Nilothauma flabellatum Adam & Sæther, 1999 and Nilothauma kakumense Adam & Sæther, 1999 as the anterior T IX projection has long apical setae forming fan-like structures. The differences between these three species are given in Table 2.

Distribution.

Oriental China (Yunnan Province).

Biological note.

The males were collected at the bank of Mengsuo Lake by light trap, where the nutrient levels are relatively high (conductivity 39−42 μs /cm, chlorophyll-a 10.5−11.1 μg /l). The co-occurring dominant species are eutrophic taxa, such as Kiefferulus sp., Polypedilum nubeculosum (Meigen), Polypedilum sordens (van der Wulp), and Tanytarsus oscillans Johannsen.