Nilothauma Kieffer

Mendes, Humberto Fonseca & Andersen, Trond, 2009, Neotropical Nilothauma Kieffer, 1921, with the description of thirteen new species (Diptera: Chironomidae), Zootaxa 2063, pp. 1-45 : 9-12

Nilothauma Kieffer

Nilothauma Kieffer, 1921a: 270 .

Nilothauma Kieffer ; Freeman (1957: 424), Saether (1977: 164), Cranston et al. (1989: 394), Adam and Saether (1999: 5). Neelamia Soponis, 1987: 18 . Syn. n.

Neelamia Soponis ; Spies and Reiss (1996: 71).

Kribioxenus Goetghebuer, 1928: 18 .

Kribioxenus Goetghebuer ; Edwards (1929: 396), Townes (1945: 34), Niitsuma (1985: 229). Paranilothauma Soponis, 1987: 11 . Syn. n.

Paranilothauma Soponis ; Spies and Reiss (1996: 71), Adam and Saether (2000: 20). Toyayusurika Sasa, Suzuki et Sakai, 1998: 52.

Type species. Nilothauma pictipenne Kieffer, 1921b: 37 ; by subsequent monotypy ( Kieffer 1921b: 37).

Included species. Palaearctic Region: N. brayi ( Goetghebuer, 1921: 173) as Chironomus , Europe, Japan. N. hibaraquartum Sasa, 1993: 74 , Japan. N. hibaratertium Sasa, 1993: 73 , Japan; syn. Tosayusurika simantoefea Sasa, Suzuki et Sakai, 1998: 52 ( Adam & Saether 1999) . N. japonicum Niitsuma, 1985: 230 , Japan, [also Oriental Region]; syn. Kribioxenus jintuprimum Sasa, 1990: 32 ( Adam & Saether 1999) . N. nojirimaculatum Sasa, 1991: 86 , Japan, [also Oriental Region]. N. sasai Adam et Saether, 1999: 61 , Japan.

Nearctic Region: N. babiyi ( Rempel, 1937: 274) as Chironomus , Canada, USA. N. bicorne ( Townes, 1945: 35) as Kribioxenus , Canada, USA. N. mirabile ( Townes, 1945: 35) as Kribioxenus , USA. N. verrucum Adam et Saether, 1999: 35 , Canada.

Afrotropical Region: N. anderseni Adam et Saether, 1999: 75, Tanzania. N ankasense Adam et Saether, 1999: 27 , Ghana. N. burmeisteri Adam et Saether, 1999: 38 , Ghana, D. R. Congo. N. duminola Adam et Saether, 1999: 27 , Ghana. N. flabellatum Adam et Saether, 1999: 90 , Ghana. N. fuscina Adam et Saether, 1999: 30 , Ghana. N. harrisoni Adam et Saether, 1999: 87 , South Africa. N. insolitum Adam et Saether, 1999: 73 , Ghana. N. kakumense Adam et Saether, 1999: 93 , Ghana. N. latocaudatum Adam et Saether, 1999: 75 , Zimbabwe. N. pictipenne Kieffer, 1921b: 37 , Sudan, Chad, Guinea, Ivory Coast, Nigeria, Senegal, Togo.

Oriental Region: N. acre Adam et Saether, 1999: 69, China ( Yan et al. 2005). N. mergae Adam et Saether, 1999: 51 , Thailand. N. japonicum Niitsuma, 1985: 230 , China, Thailand ( Adam & Saether 1999; Wang 2000; Yan et al. 2005), [also Palaearctic Region]. N. nojirimaculatum Sasa, 1991: 86 , China ( Wang 2000; Yan et al. 2005), [also Palaearctic Region]. N. quatuorlobum Yan, Tang et Wang, 2005: 214 , China.

Australian Region: N. adunatum Adam et Saether, 1999: 53, Australia. N. infissum Adam et Saether, 1999: 55 , Australia.

Neotropical Region: N. aleta Roback, 1960: 101 , Peru. N. amazonense sp. n., Brazil. N. aripuanense sp. n., Brazil. N. calori sp. n., Brazil. N. complicatum sp. n., Brazil. N. duena Roback, 1960: 101 , Peru. N. fazzariense sp. n., Brazil. N. fittkaui ( Soponis, 1987: 19) as Neelamia , comb. n., Brazil; syn. Neelamia bergeri Soponis, 1987: 21 , syn. n. N. involucrum sp. n., Brazil. N. jaraguaense sp. n., Brazil. N. longissimum sp. n., Brazil. N. matogrossense sp. n., Brazil. N. reissi ( Soponis, 1987: 13) as Paranilothauma , comb. n., Brazil. N. roquei sp. n., Brazil. N. sooretamense sp. n., Brazil. N. spiesi sp. n., Chile. N. strebulosum ( Adam et Saether, 2000: 21) as Paranilothauma , comb. n., Costa Rica. N. zitoi sp. n., Brazil.

Remark. The gender of the genus name Nilothauma is neuter because the final part of this compound word, the Ancient Greek noun 'thauma', is neuter in gender. Thus Paranilothauma strebulosum Adam et Saether, 2000 has been changed accordingly (see ICZN 1999: Article 34.2).

Diagnostic characters. Most males can be separated from all other Chironomini by the presence of at least one dorsal lobe on tergite IX. Some Neotropical species lack dorsal lobe(s) on tergite IX, but can be recognized by the absence of anal point and a long digitiform inferior volsella. They differ from other Chironomini except some Paratendipes also by the combination of antenna with 13 flagellomeres, antennal ratio generally low (AR <0.40, except in N. longissimum sp. n.), bare squama, VR generally high, anterior tibia with long spur, midtibia with one or occasionally two spurs, and hind tibia with two spurs.

The pupae can be separated from all other Chironomini on the shape of the thoracic horn consisting of 4–8 slender branches, segment IV with 1 taeniate lateral seta, segments V–VIII with 4 taeniate lateral setae, and anal lobe with 1 long, taeniate dorsal seta.

The larvae can be separated from all other Chironomini by the bean-shaped head in lateral view, antenna with 6 segments with basal segment shorter than flagellum, Lauterborn organs absent, and pale mental and mandibular teeth.

Imagines. Small species, with wing length 0.7–2.8 mm. Body pale or green to golden brown; legs pale or golden brown to brown; in some species forefemur with darker rings basally and apically; in one species ( N. longissimum sp. n.) abdomen with dark oral bands.

Head. Eyes bare or occasionally hairy, with dorsomedial parallel-sided extension, almost in contact medially. Male antenna with 13 flagellomeres; with sparse, short plume; stout subapical seta present or absent; antennal ratio generally low (AR <0.40), one species ( N. longissimum sp. n.) with AR> 1.00. Female antenna with 6 flagellomeres. Frontal tubercles present or absent. Maxillary palp with 5 segments, third segment with 2–5 long sensilla clavata subapically. Temporal setae uniserial consisting of inner verticals, outer verticals, and postorbitals.

Thorax. Antepronotal lobes reduced and dorsally narrowed, occasionally with weak dorsal notch on each side of median suture. Scutal tubercle absent, scutum not overreaching antepronotum. Dorsocentrals uniserial, few to several, widely spaced; acrostichals present, biserial; prealars and scutellars few.

Wing. Wing membrane without macrotrichia, finely punctuated, sometimes with pattern of dark spots, anal lobe reduced to completely lacking. Costa not extended beyond tip of R4+5, ending before apex of wing and proximal to M1+2; R2+3 ending midway between tips of R1 and R4+5; Cu1 curved; FCu far distal to RM resulting in very high venarium ratios. R, R1, and R4+5 generally with setae, R1 occasionally bare. Squama bare.

Legs. Apex of foretibia with narrow conical scale bearing long, curved spur at most only slightly offset from the scale. Apical combs of mid- and hind tibiae well separated, midtibia with one or occasionally two short spurs, hind tibia with two short spurs. Sensilla chaetica apparently absent, or mid ta1 with few sensilla chaetica (1–4), occasionally also present on hind ta1, additional sensilla-like setae distributed along full length of hind tarsi. Pulvilli very short or absent.

Abdomen. Abdominal tergites with few setae, often with setae arranged in transverse rows. Segment VIII variably triangular, tapering orally.

Hypopygium. Tergite IX without or with medially separated anal tergite bands along anterior margin. Tergite IX without or with one to several dorsal projections. If more than one projection, anterior projection simple, medially divided or split in two separate lobes, generally covered with stout, occasionally apically split setae; one species ( N. roquei sp. n.) with long lateral projection with microtrichia and few weak apical setae. If present posterior projection simple or double (dorsoventrally), sometimes covered with setae. If dorsal projection(s) absent tergite IX without or generally with few strong dorsal setae; one species ( N. aripuanense sp. n.) with tergite IX more densely covered with strong setae. Posterior margin of tergite IX generally with several short setae, when anal point present often in groups flanking base of anal point. Anal point present or absent; when present, usually broadly lanceolate and slightly to strongly bent ventrad; in some species nearly parallel-sided; often transparent; sometimes with microtrichia in basal half or apparently with median ridge with microtrichia. Laterosternite IX without or with few setae, occasionally with strong thorn.

Inferior volsella slender, digitiform, slightly to strongly curved; in one species ( N. complicatum sp. n.) with subapical branch; with microtrichia at least apically; with apical, strong simple or apically split setae, often sitting on small tubercles. Superior volsella highly variable: generally broadly lobe-shaped to pediform; sometimes curved, digitiform or slender parallel-sided; occasionally diamond-shaped with ventral fold; occasionally with lateral spine; generally totally covered with microtrichia or with microtrichia in apical half, occasionally without microtrichia; generally with few strong to weak apical to subapical setae, occasionally with single strong apical setae or without setae, one species ( N. complicatum sp. n.) with lateral row of flattened setae subapically. Median volsella moderately long to very short, sometimes apparently fused with superior volsella and recognizable only by few strong setae sitting mediobasally on superior volsella, occasionally absent; when present digitiform, tubercle-like or cleft; with or without microtrichia; generally with one to few strong apical setae, often sitting on small tubercles. Median volsella might be asymmetrical with left and right volsellae different in length, position and shape.

Transverse sternapodeme usually absent or when present without oral projections; when absent often with median oral elongation or apodeme thickened medially. Gonocoxite with few (2–7, generally <5) inner ventral setae. Gonostylus narrow, apically distinctly swollen to tapered; generally with short apical seta sitting on small tubercle; distomedially with row of few thin simple or apically split setae.

Female genitalia. Gonocoxapodeme VIII straight, ending on gonapophysis VIII. Gonapophysis VIII apparently divided; ventrolateral lobe usually vestigial and hidden underneath dorsomesal lobe, occasionally better developed and brush-like. Dorsomesal lobe broad, and rounded or straight caudally. Apodeme lobe very weak, perhaps occasionally absent. Tergite IX normal. Gonocoxite IX bare or at most with a few setae. Coxosternapodeme nearly straight. Segment X without setae. Postgenital plate comparatively large, triangular. Cerci of moderate size. Seminal capsules comparatively small, oval with distinct cylindrical neck. Spermathecal ducts straight, conspicuously wide.

Pupa. Small to medium sized, 2.6–4.5 mm long. Exuviae pale to light brown with caudal spur brown.

Cephalothorax. Cephalic tubercles and frontal warts absent. Frontal setae short, not on tubercles. Frontal apotome smooth or slightly wrinkled anteriomedially. Thoracic horn of 4–8 slender filaments, one of them with few spines; basal ring oval. Prealar tubercle weakly developed. Scutum with few weak tubercles. Wing sheath smooth. Two precorneals, 2–3 antepronotals and 4 dorsocentrals present.

Abdomen. Tergite I bare or with few minute spinules; tergites II–VI with transverse anterior band of somewhat stronger spinules, merging with median field of finer shagreen; anterior band of shagreen on tergite VI separated from posterior shagreen patch; tergite VII generally with anterior patch (absent in N. aripuanense sp. n.) and 1 posteromedian or 2 smaller posterolateral patches, anterior and posterior patches sometimes connected by band of fine shagreen; tergite VIII with two very small anterior patches (occasionally lacking) and variable large median, usually triangular patch of strong to less strong shagreen, sometimes with posterior shagreen patch separated from or connected with median patch; tergite IX bare. Sternites I–VII bare; sternite VIII with central, longitudinal field of shagreen. Tergite II with continuous row of caudal hooklets, occupying about 2/3 width of segment. Conjunctive III/IV with 4–7 rows of spinules; conjunctive IV/V with 1–7 rows of spinules. Pedes spurii A absent. Pedes spurii B weakly developed on segment II, occasionally absent. Segment VIII with anal comb consisting of one main spur and one to several accessory teeth or more anterior spines.

Abdominal setation. Segment I without L setae, occasionally with 1 weak L seta; segments II and III each with 3 hair-like L setae; segment IV with 2 anterior hair-like L setae and 1 posterior taeniate LS seta; segments V–VIII each with 4 taeniate LS seta. Tergites and sternites with 1 pair of O setae.

Anal lobe. Well developed with complete fringe of 19–47 long taeniae in single row; 1 long taeniate dorsal setae present.

Larva. Small, up to 7 mm long. Color red. With 2 pairs of contiguous eyes. Head rather long, beanshaped in lateral view.

Dorsal surface of head. Frontal apotome and clypeus present, equally broad. Labral sclerites 1 and 2 not discernible.

Antenna. With 6 segments, basal segment at most as long as flagellum; antennal segment 2 long, segment 3 shorter than segments 2 and 4; segment 4 slightly shorter to slightly longer than segment 2; segment 5 about as long as segment 3; ultimate segment minute. Basal antennal segment with ring organ situated in distal 1/4; seta absent. Lauterborn organs absent. Style well developed. Blade unusually broad, arising from apex of basal segment, shorter than flagellum. Accessory blade short and slender.

Labrum. S I plumose distally; S II simple; S III slender and as long as S II; S IV comparatively large. Labral lamella consisting of 6 isolated toothlets. Pecten epipharyngis trifid, consisting of 3 basally fused toothlets. Seta premandibularis simple. Premandible with 3–4 teeth.

Mandible. All teeth pale; dorsal tooth not prominent, but a broad tooth is often present subapically on inner side; with very slender and long apical tooth, not in the same plane as 4 inner teeth; inner teeth occasionally with a common base and dorsal tooth absent. Seta subdentalis slender and long, weakly curved into S-shape distally. Seta interna and pecten mandibularis apparently absent.

Mentum. Pale, divided into 3 parts; median teeth set off from lateral parts and in contact with anteriorly produced median ends of ventromental plates; middle part usually consisting of 2 pale, small to minute inner teeth and usually slightly darker pair of outer median teeth. All 4 median teeth may be worn to different degree and may appear as a single median tooth; occasionally middle part consisting of 6 small median teeth; each lateral part of mentum with 6 pairs of slender, pointed, medially curved teeth which become progressively smaller laterad. Ventromental plates medially separated by about 1/2 width of mentum; about 1.5 times as wide as mentum; striae in basal 1/2 of ventromental plates. Setae submenti very long and strong, situated comparatively deep on submentum.

Abdomen. Lateral and ventral tubules absent. Anal tubules shorter than posterior parapods, with broad base and convexly tapering to blunt apex. Procercus with 7–12 long anal setae. Supraanal setae long, at least 2/3 as long as anal setae.

Remarks. The above diagnoses are based on Adam and Saether (1999), Cranston et al. (1989), and Pinder and Reiss (1983, 1986), including the diagnoses for Neelamia and Paranilothauma ( Adam & Saether 2000; Soponis 1987). From the Neotropical Region pupae of only three named species are known in addition to two unassociated pupae. No larvae are described from the Neotropical Region. However, Trivinho-Strixino and Strixino (1995) recorded two different Nilothauma - type larvae from São Paulo State; according to S. Trivinho-Strixino (personal communication) these larvae do not have mentum with pale median teeth as described above. Some Brazilian larvae identified to Omisus Townes might also belong in Nilothauma .