New Species of Rheotanytarsus Thienemann and Bause ( Diptera : Chironomidae : Tanytarsini ) from Darjeeling – Sikkim , Himalaya , India , with Revised Keys to the Adult Males and Pupae of the Species of the Oriental Region

Three new species ofRheotanytarsusThienemann and Bause are described and illustrated from India.R. nudicornus n. sp. belonging to the aquilus species group is described as adult male and pupa, R. spinicornus n. sp. in the muscicola group is described as adult male, pupa, and larva, and R. caputimberus in the trivittatus group is described as adult male with damaged pupa. A possible placement and inclusion of these three new species from India and other seven species recorded from the Oriental China in the key to males of genus Rheotanytarsus of Kyerematen et al. are proposed. A probable placement and inclusion of the 2 new species from India in the key to pupae of Rheotanytarsus of Kyerematen et al. are also stated. Diagnoses of the muscicola group and trivittatus group are emended.


Introduction
The genus Rheotanytarsus Thienemann and Bause is a diverse predominant group occurring in nearly all lotic water recorded from all biogeographic regions except Antarctica comprising more than 100 nominal worldwide species [1].The larvae of Rheotanytarsus are rheobiontic, filter feeding using nets stretching between the anterior "arms" of their characteristic cases.The silk mesh retains suspended detritus from the water flowing past the case.Detritus are utilized as food and for dwelling material by the larvae [1].Most larvae live in moderately fast-to-slow flowing rivers, streams, and creeks and rarely in stagnant water-more likely in nearshore habitats in wind-driven currents on lakes [2].The larvae may be phoretic on a number of other aquatic invertebrates including naiads of odonates, may flies, larvae of caddis flies, megalopteran insects, and gastropod molluscs [3].
Most species are described based on male adults including their distinctive genitalia; fewer are also known from their immature stages as Lehmann [4] described many western European species with their pupae while Cranston [5] did for Australian ones."Composition of tentative species groups" of the genus Rheotanytarsus based on both pupal exuviae and adult males made by Saether and Kyerematen [6] has been followed here.Of the three new species, R. nudicornus n. sp.belongs to the aquilus species group described as adult male and pupa, R. spinicornus n. sp. in the muscicola group as adult male, pupa, and larva, and R. caputimberus n. sp. in the trivittatus group as adult male and damaged pupa.A possible position and insertion of these three proposed Indian species and other seven species reported from Oriental China [7] including four species, namely, R. bullus, R. liuae, R. polychaetus, and R. quadratus described by Wang and Guo [7], R. tamatertius Sasa of Palaearctic Japan, R. buculicaudus Kyerematen, Andersen & Saether of Ghana and R. muscicola Thienemann of Holarctic Region including Palaearctic China in the key to known males of genus Rheotanytarsus of Kyerematen et al. [2] are proposed.A probable placement and inclusion of the 2 new species from India in the key to known pupae of Rheotanytarsus of Kyerematen et Psyche al. [2] are also provided.Moubayed described Rheotanytarsus orientalis [8] and Rheotanytarsus thailandensis [9] from Thailand.Kyerematen et al. [2] made a review of the 26 species of Oriental Rheotanytarsus.Chaudhuri et al. [10] recorded four species of the genus from India.Later Wang & Guo [7] reviewed the genus from China stating seven species from Oriental China.With the addition of three new species here described, the number of species now increases to seven from India and thirty-six from the Oriental Region.Diagnoses of the muscicola group and trivittatus group are emended after examination of Rheotanytarsus spinicornus n. sp. and Rheotanytarsus caputimberus n. sp., respectively.

Material and Methods
The larvae collected from the streams of the Darjeeling-Sikkim, Himalaya, were reared in the glass vials containing substratum of the natural habitat plugged with cotton.The specimens were mounted on microslides following the method of Hazra et al. [11].Morphological terminologies and abbreviations follow Saether [12] and Epler et al. [1].Measurements are expressed in micrometers (m) except the total length and wing length which are in millimetres (mm) with the ranges suffixed by "" in parentheses denoting the number of specimens considered.

Etymology.
From the Latin nudus, bare, and cornus, horn, referring to the bare thoracic horn of the pupa.

Abdomen (Figures 2(d)-2(g)).
Tergite I bare.Tergites II-V with anterior pair of spines of circular patches.Tergites III-V with extensive shagreen present posterior of circular patches extending over and beyond the first dorsal seta, most pronounced on tergite V. Pair of circular patches on tergite V smaller than others.Median shagreen essentially absent,     [7], with 12 flagellomeres and gonostylus not abruptly narrowed by the following combination of characters: (i) anal tergite band V-shaped not joined by basal tergite band, (ii) anal crest narrowly V-shaped and open at the base, (iii) superior volsella oval with knob-like small apical projection, (iv) subulate setae of median volsella fused to form a plate in adult male, and (v) bare thoracic horn, without a median bend, (vi) tergites II-V with anterior pair of spines of circular patches, (vii) posterior spinules on tergite II undivided, and (viii) anal lobe with hair-like dorsal seta of the pupa.

The muscicola Group [6]
Emended Diagnosis.Anal lobe of pupa with or without dorsal seta and superior volsella of male with or without knob-like or slightly hooked posterior extension.

Etymology.
From the Latin spina, spine, and cornus, horn, referring to the numerous/many spinules of the thoracic horn of the pupa.

Description
Adult Male ( = 5) (Figure 3).Total length    Maxilla.Maxilla as in the Figure 5(f).[14] in basal tergite band but differs in shape of anal point.The pupa appears similar to those of R. muscicola Thienemann [15] and R. photophilus [16].Larval characters such as antenna, mandible, premandible, and mentum show resemblances with Rheotanytarsus sp. 1 described by Roback & Coffman [17] from Nepal Alpine zone.In spite of the above similarities, the following combination of characters separates the new species from other members of the muscicola group in (i) V-shaped anal tergite band with medially joined basal tergite band, (ii) anal crest roughly V-shaped and open, (iii) median volsella not reaching the apex of superior volsella with subulate apical setae fused into a plate, (iv) gonostylus longer than gonocoxite and abruptly narrowed distally in adult male, (v) numerous spinules on distal 2/3 of thoracic horn without a median bend, (vi) tergites II-V with anterior pair of spines of circular patches, (vii) posterior spinules on tergite II undivided, (viii) anal lobe with hair-like dorsal seta on pupa, (ix) pecten epipharyngis, a single broad distally serrated plate, (x) median tooth of mentum with 2 indistinct notches laterally, and (xi) mandible with 3 inner teeth on larva.

The trivittatus Group [6]
Emended Diagnosis.Median volsella reaching or not reaching beyond the apex of superior volsella and basal anal tergite band joined at the middle or interrupted in adult male.

Etymology.
From the Latin caput, head and imber, shower, referring to shape of the inferior volsella similar to the 10 Psyche  head of hand shower, and the suffixus denoting the gender of the genus.

Description
Adult Male ( = 2) (Figure 6).Total length Legs.Spur of fore tibia (ti) 21 m long; spurs of mid tibia unequal 30 m and 24 m long including 17-18 of comb; spurs of hind ti 21 m and 9 m long including 14-15 of comb.
Width at the apex of fore tibia 33 m; mid tibia 36 m; hind tibia 30 m.Lengths and proportions of leg segments as in Table 3. Pupa ( = 1) (Mostly Damaged) (Figure 7).Exuviae pale with outer edge of cephalothorax and margins of tergite VIII darker.
(1) Tergite VIII with caudolateral comb; T II-V with anterior paired patches of spinules; thoracic horn with knee-like bend, heavily sclerotized 2 Tergite VIII with single spur; T II-IV, II-V or II-VI with paired patches of spinules; thoracic horn may be sharply bent but not knee-like 3 3.3.4.Remarks.Rheotanytarsus caputimberus n. sp.shows affinity with other members of the group having projections to each side of the anal point except R. scutulatus Kyerematen & Andersen [14].Similarly superior volsella of the new species is similar to other members of the group except R. ramirezae Kyerematen [14] and R. scutulatus Kyerematen & Andersen [14].Gonostylus is abruptly tapered like other members except in R. ceratophylli [18] and R. trivittatus Johannsen [19] In spite of the above, the proposed species may be separated from other members of the trivittatus group including oriental species R. brevipalpus Wang & Guo [7], R. additus [19], and R. trivittatus Johannsen and may be diagnosed by the following combination of characters: (i) lateral projections on each side of the anal point, (ii) basal anal tergite band medially joined, (iii) superior volsella ovoid, (iv) median volsella not reaching beyond apex of superior volsella with subulate setae fused into plate, (v) inferior volsella typically like head of hand shower, and (vi) gonostylus abruptly tapered.Key to adult males of Oriental Rheotanytarsus Thienemann and Bause (modified after Kyerematen et al. [2]) is shown in Table 4 while Table 5 shows key to pupae of Oriental Rheotanytarsus Thienemann and Bause (modified after Kyerematen et al. [2]).
(a)) 114 long, 7 width at base without any median bend, bearing few spinules at the basal region.Thorax smooth, wing sheath with prominent nose (Figure 7(b)), 21 long.Antepronotals two, median one 136-140 long and lateral

( 2 )
Hook row of about 90 hooklets; anal lobe fringe of much less than 20 taeniae additus(Johannsen)   Hook row of 60-70 hooklets; anal lobe fringe of about 20 taeniae trivittatus (Johannsen) (3) Thoracic horn sharply bent at midlength; T II-IV with oral, paired, rounded patches of spinules 4 Thoracic horn not sharply bent; T II-V or II-VI with spinule patches 5 (4) Tergite VIII with 3 lateral taeniae thailandensis Moubayed Tergite VIII with 5 lateral taeniae oss Cranston (5) Tergites II-VI with sharply defined, paired spinule patches 6 Tergites II-V with sharply defined patches of spinules 7 (6) Anal lobe with one large dorsal seta; thoracic horn with few fine spinules curtistylus (Goetghebuer) Anal lobe with two short dorsal setae; thoracic horn with many fine spinules in distal half orientalis Moubayed (7) Anal lobe without dorsal setae; distal half of thoracic horn with many spinules adjectus (Johannsen) Anal lobe with long dorsal setae; distal half of thoracic horn with or without any spinules 8 (8) Distal half of thoracic horn without any spinules nudicornus n. sp.Distal half of thoracic horn with few to many spinules 9 (9) Tergites II and III with transversely elongated or rectangular spine patches reissi Lehmann Tergites II-III with circular or elliptical spine patches 10 (10) Numerous spinules on distal 2/3 of the thoracic horn spinicornus n. sp.Spinules few on distal 1/3 of the thoracic horn tamaquartus Sasa one 40-44 long.Precorneals three, anterior one 72 long, lemelliform; median one 48 long, lamelliform and posterior not seen.Dorsocentrals Dc 1 and Dc 2 paired 12 and 9 long respectively and Dc 3 and Dc 4 also paired, 12 and 18 long respectively; distance between two paired dorsocentrals 51.Abdomen.Tergites II-V with circular anterior pair of spine patches.Tergites III-V with shagreen next to circular patches extending over and beyond the first dorsal seta.Pair of circular patches on tergite V smaller than others.Number of spines on patches on tergites II-V: 75-80; 67-70; 38-40; 34-35.Hook row small, occupying 0.057 width of the segment, containing about 12-13 hooklets.Most of the abdominal segments including anal lobe damaged except segment VI (Figure 7(c)); segment V with 4 LS setae; VI 4 LS setae.

Table 2 :
Lengths (m) and proportions of leg segments.

Table 3 :
Lengths (m) and proportions of leg segments.