Nilothauma bilobatum, 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 : 149-151

Taxon classification Animalia Diptera Chironomidae

Nilothauma bilobatum sp. n. Figs 25-32, 33-40

Type material.

Holotype: male with associated pupal exuviae (EJNU), CHINA: Guangxi Zhuang Autonomous Region, Guilin City, Qingshitan Reservoir, 25°31.640'N, 110°13.499'E, Alt. 235 m, 26.viii.2014, Long Term Ecology Research Group (LTER), light trap. Paratypes: 2 males with pupal exuviae as holotype (EJNU); 1 male and 1 female pupa (EJNU), CHINA: Guangdong Province, Shantou City, Nan’ao county, Shen-Ao Reservoir, 23°28.390'N, 117°06.683'E, Alt. 61m, 17.iv.2015, Tang HQ, light trap.

Diagnosis.

The male of Nilothauma bilobatum sp. n. can be distinguished from other Nilothauma species by the following combination of characters: anterior T IX projection bearing simple setae only; anal point broadly lanceolate with microtrichia; superior volsella with a lateral spur, a main lobe bearing 4−5 apical setae, and a blunt-tipped lobe bearing a terminal seta, without microtrichia. The pupa can be separated from others by the following characters: relatively short frontal setae (as long as or slightly longer than the major axis of basal ring); and anal comb of abdominal segment VIII consisting of a main spur and 2−3 accessory spines.

Etymology.

From Latin bi- (two) and lobatus (lobate), referring to the male hypopygium with two lobes in the superior volsella.

Description.

Male imago (n = 4).

Total length 2.4−3.1 mm. Wing length 1.2−1.6 mm. Total length/wing length 1.6−2.7. Wing length/length of profemur 2.0−2.5.

Coloration. Generally pale yellow. Wing without any marking. Foreleg entirely yellowish brown; mid and hind legs with femora and tibiae pale yellow, and tarsus yellowish brown.

Head. AR 0.18−0.19. Temporals 7−10. Clypeus with 12−13 setae. Tentorium 100−125 μm long, 15−25 μm wide. Stipes 120−130 μm long, 5−8 μm wide. Lengths of palpomeres 1−5 (μm): 18−25, 33−37, 55−65, 100−125, 123−165. Palpomere 3 with 2 sensilla clavata; Pm5/Pm3 2.2−2.5.

Thorax. Dorsocentrals 9−11, acrostichals 6−10, prealars 2−3, scutellars 2.

Wing (Fig. 25). VR 1.3−1.6. Brachiolum with 1 seta, R with 11−13 setae, R1 with 8−11 setae, R4+5 with 13−17 setae.

Legs. Spur of foretibia 60−80 μm long including 28−38 μm long scale (Fig. 26). Spur of mid tibia 22−25 μm long including 15−23 μm long (Fig. 27). Spurs of hind tibia 27−35 μm and 33−47 μm long, respectively (Fig. 28); comb 17−24 μm long. Width at apex of foretibia 34−42 m, of mid tibia 41−52 m, of hind tibia 48−50 m. Lengths and proportions of legs in Table 4.

Hypopygium (Fig. 29). Tergite IX with 2 dorsal projections. Anterior projection completely divided into 2 oval lobes; each 35−55 μm long, 8−10 μm wide at middle, with 12−15 simple setae 30−50 μm long. Posterior projection 28−32 μm long, 50−65 μm wide at base, 8−15 μm wide at apex, apically rounded, with 11−13 setae 20−25 μm long. Anal point (Fig. 30) very broadly lanceolate, 35−50 μm long, 13−20 μm at base, 15−20 μm at middle, with microtrichia. Posterior margin of tergite IX (Fig. 31) with 4−6 setae. Laterosternite IX with 3 setae. Phallapodeme 38−50 μm long. Transverse sternapodeme medially triangular, but without median elongation. Gonocoxite 100−120 μm long. Superior volsella 30−38 μm long, trifid; with lateral spur, main lobe bearing 4−5 apical setae, and blunt-tipped lobe terminating in seta; without microtrichia. Median volsella (Fig. 32) 20−30 μm long, with microtrichia and 4−6 apical setae. Inferior volsella 80−94 μm long, pointed apically, microtrichiose, with 7−8 simple apically split setae. Gonostylus 130−160 μm long, with 7−10 simple median setae in distal 1/3. HR 0.63−0.88, HV 1.5−2.4.

Pupa (n = 4).

Total length 5.0−5.6 mm. Exuviae yellow with posterior antepronotum and anal comb on abdominal segment VIII brown.

Cephalothorax (Fig. 33). Frontal apotome smooth. Frontal seta short, 38−40 μm long (n = 2). Basal ring oval with major axis 30−40 μm long, the posterior usually with 2−3 small tubercles. Frontal seta 1.0−1.2 times as long as major axis of basal ring. Thorax with one patch of small granules on each side of median suture.

Abdomen (Fig. 34-35). T I without spinulation; T II−V extensively spinulated; T VI−VII with anterior and posterior bands of spinules; T VIII with anterolateral and median spinulation; T IX with median spinulation in female pupa (Fig. 34), but without any spinulation in male. Anterior spinulation on T II–VIII consisting of somewhat large spinules. S I−III and IX without spinulation; S IV−VI with weak posterolateral spinulation; S VII−VIII with weak anterolateral and strong median spinulation, occasionally these merging into extensive spinulation in S VIII (Fig. 39, 40). Tergite II with row of 60−85 caudal hooklets. Conjunctives III/IV and IV/V with rows of spinules. Pedes spurii B distinct on segment II. Anal comb of segment VIII (Fig. 36-38) composed of main spur 30−50 μm long, and 2 or 3 accessory spines 10−30 μm long. Anal lobe 250−280 μm long, 1.8−2.2 times as long as broad, with 41−50 lateral setae, dorsal setae located near the distal margin of disc.

Female imago and larva. Unknown.

Remarks.

The male of Nilothauma bilobatum sp. n. is similar to that of Nilothauma mirabile (Townes, 1945) as the superior volsella has a lateral spur and two setigerous lobes, but separable by the anterior T IX projection bearing simple setae only and the anal point covered with microtrichia. In Nilothauma mirabile , the anterior projection has apically plumose setae and the anal point is bare. The pupa of Nilothauma bilobatum sp. n., as well as that of Nilothauma aristatum sp. n., will key to " Nilothauma sp. Australia" in Adam and Sæther (1999). The pupa resembles that of Nilothauma aristatum sp. n., rather than that of Nilothauma sp. Australia, in having relatively short frontal setae (1.0−1.2 times as long as the major axis of basal ring), but differs in the anal comb of abdominal segment VIII consisting of a main spur and 2−3 accessory spines. In Nilothauma aristatum sp. n., the anal comb has a main spur and a single accessory spine.

Distribution.

Oriental China (Guangxi Zhuang Autonomous Region and Guangdong Province).

Biological note.

The material was collected from two relatively eutrophic reservoirs (conductivity 24−65 μS /cm, dissolved oxygen 6.6−8.3 mg/l). The adults of the following species also occurred from there: Glyptotendipes tokunagai Sasa, Dicrotendipes pelochloris (Kieffer), Tanytarsus oscillans Johannsen, Cladotanytarsus paratridorsus Wang & Guo, and Polypedilum masudai (Tokunaga).