Notes on Nilothauma Kieffer from Oriental China, with descriptions of three new species (Diptera, Chironomidae)

Abstract Three new species of Nilothauma Kieffer are described and figured from Oriental China: Nilothauma angustum sp. n. based on the male only, Nilothauma aristatum sp. n. based on the male, pupa and larva, and Nilothauma bilobatum sp. n. based on the male and pupa. In addition, new distribution records are given for Nilothauma japonicum Niitsuma, Nilothauma nojirimaculatum Sasa, Nilothauma hibaratertium Sasa, and Nilothauma acre Adam & Sæther. A key to known males of Nilothauma Kieffer in China is provided.


Introduction
The genus Nilothauma Kieffer, 1921 is represented by 43 species: six species occurring in the Palaearctic region, four in the Nearctic region, 16 in the Neotropical region (not including N. aleta Roback and N. duena Roback due to the uncertain status), six species in the Oriental region, 11 species in the Afrotropical region, two species in the Australasian region, and two species occuring both in the Palaearctic and Oriental regions (Adam and Saether 1999;Mendes and Andersen 2009;Qi et al. 2014). From China, five species have been recorded: N. japonicum Niitsuma, N. nojirimaculatum Sasa, N. acre Adam & Saether, N. quatuorlobum Yan, Tang & Wang, and N. pandum Qi, Lin, Wang & Shao; all in the Oriental part of the country. No adult information is available on the genus from Palearctic parts of China.
In the present paper, we present new material of Nilothauma from Oriental China. Three species are described as new to China, and new distributional records are given for N. acre Adam & Saether, N. hibaratertium Sasa, N. japonicum Niitsuma and N. nojirimaculatum Sasa. We also present an identification key to males of Nilothauma in China.

Materials and methods
Descriptions of morphological characters are based on slide-mounted specimens in Euparal. Terminology for morphology and abbreviations follow Saether (1980) and Adam and Saether (1999).
Most of the specimens examined here are deposited in the College of Life Science, Taizhou University (LTZU) and partial in Nankai University (LNKU). The holotype specimens of three new species are deposited in the Ecology Department, Jinan University (EJNU).
Diagnosis. The adult male of N. 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.
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. Diagnosis. The adult male of N. aristatum sp. n. can be distinguished from other known Nilothauma species by the anterior T IX projection with plumose setae; the anal point broadly lanceolate with microtrichia along the median ridge; the superior volsella slender with a lateral spur, and one lateral and 2−3 apical setae, without microtrichia. The pupa is characterized by the relatively short frontal setae (1.5−2.0 times as long as the major axis of basal ring); and the anal comb of abdominal segment VIII consisting of a main spur and a single accessory spine. The larva cannot be reliably separated from those of other species.  Etymology. From Latin aristatus (aristate), referring to the male hypopygium with a lateral spur on the superior volsella.
Cephalothorax. Frontal seta short, 30−50 μm long (n = 2). Basal ring small, stomalike, with major axis 20−25 μm long, minor axis 5−8 μm high. Frontal setae 1.8−2.0 times as long as major axis of basal ring. Thorax pebbled and rugose dorsally. Abdomen (Fig. 18). Tergite I without spinulation; T II−VI extensively spinulated; T VII with anterior and posterior bands of spines; T VIII with anterolateral and median bands of spines; tergite T IX with median spinulation in female (Fig. 21), but without any spinulation in male. S I−II without spinulation; S III−IV with anterior spinulation; sternite IV with weak anterolateral spinulation; S V with weak anterolateral and caudolateral spinulation; S VI−VIII with anterolateral and median spinulation, occasionally anterolateral spinulation merged to median in S VIII (Fig. 20). T II with row of 70−78 caudal hooklets with posterior groups of points behind each end. Conjunctives III/IV and IV/V with rows of spinules. Pedes spurii B weakly developed on segment II. Anal comb of segment VIII (Fig. 19) composed of main spur 20−30 μm long and single accessory spine 7.5−17.5 μm long. Segment I without L-setae; segments II-III each with 3 L-setae on each side; segment IV with 2 L-setae and 1 LS-seta on each side; segments V-VIII each with 4 LS-setae on each side. Anal lobe 200−240 μm long, 2.4−2.6 times as long as broad, with 35−48 lateral setae, dorsal seta located near distal 1/3. Larva (n = 1). Total length 5 mm. Head capsule about 300 μm long, about 260 μm wide.
Coloration. Red color in fresh specimens, head pale yellow. Mentum and postoccipital margin brown.
Female imago. Unknown. Remarks. The male is similar to that of Oriental species N. acre Adam & Saether, 1999 in having the wing unmarked, the anterior T IX projection with plumose setae, the anal point lanceolate, and the superior volsella slender with a lateral spur and one lateral and two three apical setae. It differs from it as the anal point bears microtrichia along the median ridge, the superior volsella is relatively long compared to the median volsella (length ratio, Svo/Mvo > 4.0) and the inferior volsella has simple setae only. In N. acre, the anal point is bare, length of Svo/Mvo is around 2.0 and the inferior volsella has apically split setae.
The pupa of N. aristatum sp. n. will key to "N. sp. Australia" in Adam and Saether (1999), but may be separable by the relatively short frontal setae. The ratio of the length of the frontal seta to the length of the major axis of basal ring is 1.8−2.0 in N. aristatum sp. n., but 4.6−6.5 in the latter. The larva of N. aristatum sp. n. somewhat resembles that of N. japonicum Niitsuma, 1985, but it remains uncertain because of a paucity of data.
Biological note. The larva and pupa of N. aristatum sp. n. are found in first-, or second-order streams. The water is relatively clean and cold (water temperature 15°C−20°C, pH 7.80−7.88, DO% 90.6−93.4, DO 8.09−9.36 mg/l, and conductivity 25−34 μs/cm). The co-existing dominant species of chironomids are Eukiefferiella spp., Rheotanytarsus spp., Rheocricotopus spp., and Parametriocnemus spp. Some steno-thermic species, such as Heleniella sp. and Pagastia sp., are frequently observed in the pupal exuviae samples. Diagnosis. The male of N. 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.

Nilothauma bilobatum
Etymology. From Latin bi-(two) and lobatus (lobate), referring to the male hypopygium with two lobes in the superior volsella.
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 N. bilobatum sp. n. is similar to that of N. 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 N. mirabile, the anterior projection has apically plumose setae and the anal point is bare. The pupa of N. bilobatum sp. n., as well as that of N. aristatum sp. n., will key to "N. sp. Australia" in Adam and Saether (1999). The pupa resembles that of N. aristatum sp. n., rather than that of N. 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 N. 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).

Nilothauma acre Adam & Saether
Nilothauma acre Adam & Saether, 1999 Remarks. This species was described from Fujian Province in China for the first time by Adam and Saether (1999).

Nilothauma hibaratertium Sasa
Nilothauma hibaratertia Sasa, 1993 Remarks. N. hibaratertium has never been described sufficiently, especially in the coloration of the adult. Examination of fresh specimens showed that the foreleg of the adult has distinct dark markings on the base and sub-apex of femora, and the apices of tibia and tarsomere 1. This is the first record of N. hibaratertium from the Oriental region; previously, this species has only been recorded from Palaearctic Japan (Yamamoto and Yamamoto 2014).
Remarks. So far this species has been recorded from Thailand, Zhejiang and Hainan Province in China, as well as Palaearctic Japan (Adam and Saether 1999;Yan et. al. 2005;Yamamoto and Yamamoto 2014).

Nilothauma nojirimaculatum Sasa
Nilothauma nojirimaculatum Sasa, 1991 Remarks. This species was described from Palaearctic Japan and later recorded from Hainan in China (Adam and Saether 1999).