Three new Neotropical species of Nilothauma Kieffer , 1921 ( Diptera : Chironomidae )

Nilothauma canaima n. sp. from Bolı́var State in southeastern Venezuela, Nilothauma granma n. sp. from Granma Province in eastern Cuba and Nilothauma soka n. sp. from Amazonas State in Brazil are described and figured as males. N. canaima can be grouped with Nearctic Nilothauma verrucum Adam and Sæther, but can be separated based on its small size as it has a wing length <1.3 mm and an AR = 0.13. N. granma can be grouped with Nearctic Nilothauma babiyi (Rempel) and Neotropical Nilothauma matogrossense Mendes and Andersen, but can be separated from both as it has a wing with distinct, dark areas. N. soka can be grouped with Neotropical Nilothauma aripuanense Mendes and Andersen, but can be separated based on the shape of the superior volsella as it has a boot-shaped superior volsella with microtrichia only. A key is given to the males of Nilothauma from the New World.


Introduction
The genus Nilothauma was erected by Kieffer (1921) based on Nilothauma pictipenne Kieffer, 1921 from Africa.The larvae inhabit littoral and sublittoral soft sediments of lakes and flowing waters (Epler et al., 2013).Adam and Saether (1999) revised the genus and recognized 25 species.Later, Mendes and Andersen (2009) placed Paranilothauma Soponis, 1987 and Neelamia Soponis 1987 as synonyms of Nilothauma and described 13 new species from the Neotropical region.A further five new species have been described from eastern China by Yan et al. (2005) and Qi et al. (2014Qi et al. ( , 2016)), and recently Niitsuma (2016) added one new species from Japan and placed Nilothauma sasai Adam and Saether (1999) as a synonym of Nilothauma hibaratertium Sasa, 1993.
The genus is distributed in all biogeographical regions except Antarctica.So far, 20 species are recorded from the New World; four species from the Nearctic Region and 16 from the Neotropical Region (Adam and Saether, 1999;Mendes and Andersen, 2009).Below we describe and figure an additional three new Neotropical species based on males from Brazil, Cuba and Venezuela, raising the number of species known from the Neotropical region to 19.A key to the males of Nilothauma from the New World is also provided.

Materials and methods
The specimens were mounted in Canada balsam or Euparal following the procedure outlined by Saether (1969).The general morphology follows Saether (1980).Measurements are given as ranges when more than one specimen was measured.
The holotype of N. canaima is kept in the Museo del Instituto de Zoologı´a Agricola (MIZA), Facultad de Agronomı´a, Universidad Central de Venezuela, Maracay, Venezuela.The holotype of N. granma is kept in the Department of Natural History, University Museum of Bergen (ZMBN), University of Bergen, Norway.The holotype of N. soka is kept in the Invertebrate collection at the Instituto Nacional de Pesquisas da Amazonia (INPA), Manaus, Brazil; the paratypes at ZMBN.
Etymology.The species is named after Parque Nacional de Canaima.The name is to be regarded as a noun in apposition.
Diagnostic characters.The species is characterized by having a single, median anal tergite projection with few strong setae, a spatulate anal point, a pediform, microtrichiose superior volsella and an apically split median volsella.It can be separated from Nearctic Nilothauma verrucum Adam and Saether by having a wing length < 1.3 mm and an AR = 0.13, and by having a brown thorax, while the thorax in N. verrucum is greenish with brown vittae.
Legs.Spur of foretibia 54 mm long including 23 mm long scale.Midtibia with 1 spur, 17 mm long; hind tibia with 2 spurs, 29 and 36 mm long.Combs of midtibia 14 mm long, of hind tibia 19 mm long.Width at apex of foretibia 40 mm, of midtibia 41 mm, of hind tibia 52 mm.Sensilla chaetica 1 at 0.56 of ta 1 of midleg.Lengths and proportions of legs as in Table 1.

Distribution
Known from Quebrada Santa Elena in Parque Nacional de Canaima, Venezuela only.
Etymology.The species is named after Granma Province, Cuba.The name is to be regarded as a noun in apposition.
Diagnostic characters.The species is characterized by having a single, median anal tergite projection with few strong setae, a parallel-sided anal point, a pediform, microtrichiose superior volsella and a median volsella consisting of a single, conical projection with apical, strong seta.It can be separated from Nearctic N. babiyi (Rempel) and Neotropical N. matogrossense Mendes and Andersen by having a wing with distinct, dark areas.
Coloration.Head and thorax brown with darker scutum and postnotum; abdomen and legs lighter brown.Wing membrane (Fig. 5) hyaline with dark areas at RM and FCu, in cells r 4 + 5 and m 1 + 2 , and along apical 1/2 of An.
Legs.Spur of foretibia 51 mm long including 23 mm long scale.Midtibia with 1 spur, 32 mm long; hind tibia with 2 spurs, 31 and 42 mm long.Combs of midtibia 21 mm long, of hind tibia 23 mm long.Width at apex of foretibia 39 mm, of midtibia 40 mm, of hind tibia 45 mm.Sensilla chaetica 1 at 0.49 of ta 1 of midleg.Lengths and proportions of legs as in Table 2.

Distribution
Diagnostic characters.The species is characterized by lacking dorsal projection(s) on the anal tergite, having a spatulate anal point, a boot-shaped superior volsella with microtrichia only and an apically split median volsella.It can be separated from the Neotropical N. aripuanense Mendes and Andersen on the shape of the superior volsella as this species has a narrow, weakly sinuous volsella with microtrichia and few apical setae.

Distribution
Known from Reserva Soka Gakkai in Amazonas State, Brazil only.

Discussion
Most Nilothauma species can be recognized as the males have a distinct anal point and at least one dorsal, setose projection on tergite IX.Adam and Saether (1999) proposed four species groups in Nilothauma, the duminola-, babiyi-, brayi-and pictipenne groups, separated mainly on hypopygial features.The duminola-and babiyi groups have one dorsal projection only, while two projections are found in the brayi-and pictipenne groups.In the pictipenne group the wing has dark areas, while in the other groups the wing lacks dark spots or markings.The duminola-and the babiyi groups can be separated as the superior volsella is narrowly L-shaped and all apical setae on the inferior volsella are unbranched in the duminola group, while in the babiyi group the superior volsella is pediform and covered with microtrichia and the inferior volsella has at least some apically split setae.
Of the six species described from China and Japan, N. quatuorlobum Yan et al., 2005;N. pandum Qi et al., 2014;N. aristatum Qi et al., 2016;N. bilobatum Qi et al. 2016;and N. niidaense Niitsuma, 2016 all belong to the brayi species group as the wings lack dark markings and the anal tergites have two dorsal projections.Nilothauma angustatum Qi et al., 2016 has wings with dark markings and belongs to the pictipenne species group.
When placing the genera Paranilothauma Soponis, 1987 and Neelamia Soponis, 1987 as junior synonyms of Nilothauma, Mendes and Andersen (2009) broadened the generic diagnosis considerably.Species without the anal point and dorsal, setose projections on tergite IX were included in Nilothauma, while all species treated by Adam and Saether (1999) had at least one dorsal, setose projection and all species except N. insolitum Adam and Saether, 1999 (pictipenne group) from Ghana had anal points.Another distinct difference is that all the species treated by Adam and Saether (1999) had the dorsal, setose projection(s) on tergite IX placed medially, while most species from the Neotropical Region with setose projections on tergite IX have two projections placed laterally on the tergite.The exception is N. matogrossense Mendes and Andersen, 2009 from Brazil, which has a single, large, median projection with about 45 strong setae.The variation in most other characters is large and the combination of characters used by Adam and Saether (1999) to delimit their four species groups cannot be used to include most of the Neotropical species.Mendes and Andersen (2009) therefore refrained from grouping the Neotropical species.
All the new species described above have anal points.In addition, both N. canaima n. sp. and N. granma n. sp.have a single median, setose projection on tergite IX, a pediform superior volsella covered with microtrichia and apically split setae on the inferior volsella.Thus, on hypopygial features, they both fit in the babiyi group of Adam and Saether (1999) together with the North American species N. babiyi (Rempel, 1937) and N. verrucum Adam and Saether, 1999.However, N. granma n. sp. has distinct, dark areas on the wing and also in N. canaima n. sp. the wing has faint, dark areas.Wings with dark areas or spots are elsewhere only found in the pictipenne group, but the species in this group all have two dorsal projections on tergite IX.The species in this group is distributed in Africa and in Japan; no Nilothauma species with dark areas in the wing has so far been recorded from the New World.
Nilothauma soka n. sp.lacks dorsal projection(s) on tergite IX and can thus not be placed in any of the species groups suggested by Adam and Saether (1999).The only other described Nilothauma species with the anal point, but without dorsal projection(s) on tergite IX is N. aripuanense Mendes and Andersen from Brazil.However, the two species are very different in several other hypopygial features.For instance, N. soka n. sp. has a boot-shaped superior volsella with microtrichia only, while in N. aripuanense, the superior volsella is narrow and weakly sinuous with microtrichia and a few apical setae.
Based on the males, the Neotropical Nilothauma species appear to be an aggregate of species with rather unique character combinations.Some of the species can be placed in the species groups proposed by Adam and Saether (1999), but most of the species do not fit in any of the four groups.DNA sequencing should thus be attempted to develop a better understanding of the phylogeny of the genus.

Figs 10 - 12 .
dorsal view.11.Hypopygium with anal point and tergite IX removed, dorsal aspect to the left and ventral aspect to the right.12. Superior and median volsella, dorsal view.