Nilothauma aripuanense, Mendes, Humberto Fonseca & Andersen, Trond, 2009

Mendes, Humberto Fonseca & Andersen, Trond, 2009, Neotropical Nilothauma Kieffer, 1921, with the description of thirteen new species (Diptera: Chironomidae), Zootaxa 2063, pp. 1-45 : 15-17

Nilothauma aripuanense sp. n.

( Figs 9–16 )

Type material. Holotype male with pupal exuviae (reared), BRAZIL: Amazonas: Rio Aripuanã, Igarapé das Pedras, 18.i.1962, E. J. Fittkau ( ZSM). Paratype: 1 male, BRAZIL: Mato Grosso: Serra dos Parecis, Pensão Alemã, 10–11.x.1965, drift net, E. J. Fittkau ( ZSM).

Diagnostic characters. The numerous, scattered, strong setae on tergite IX combined with the absence of dorsal lobe(s), a large lanceolate anal point, and a cylindrical microtrichiose superior volsella will separate the male of N. aripuanense from all other Nilothauma species. The pupa can be separated from other known Neotropical pupae by having a thoracic horn with 6 branches and only 1 posterior shagreen patch on tergite VII.

Etymology. Named after Rio Aripuanã.

Male (n = 1, 2 for hypopygium). Total length 2.76 mm. Wing length 1.30 mm. Total length / wing length 2.13. Wing length / length of profemur 2.35.

Coloration. Thorax and legs uniformly brown.

Head. Antennae lost. Temporal setae 4 in single row including 2 inner verticals and 2 outer verticals. Frontal tubercles well developed. Clypeus with 16 setae. Tentorium 77 µm long, 18 µm wide. Stipes 113 µm long. Palp segment lengths (in µm): 20, 27, 91, 132, 166. Third palpomere with 4 sensilla clavata subapically, longest 14 µm long. Fifth palpomere / third palpomere 1.82.

Thorax. Dorsocentrals 7 in single row; acrostichals 16, biserial, starting close to anterior margin of scutum; prealars 2. Scutellum with 2 setae.

Wing. VR 1.36. Brachiolum with 1 seta, R with 13 setae, R1 with 8 setae, R4+5 with 14 setae, remaining veins bare.

Legs. Spur of foretibia 48 µm long including 23 µm long scale. Midtibia with 1 spur, 25 µm long; hind tibia with 2 spurs, 29 µm long and broken. Combs of midtibia 14 µm long, of hind tibia 14 µm long. Width at apex of foretibia 36 µm, of midtibia 36 µm, of hind tibia 36 µm. Lengths and proportions of legs as in Table 2.

Abdomen. Tergites with few setae. Segment VIII long, widest medially, weakly tapered anteriorly, with rounded anterior margin.

Hypopygium ( Figs 9–10 ). Tergite IX with broadly triangular posterior margin; without dorsal lobe(s), with 36–40 scattered strong setae, including those close to anal point. Anal point broadly lanceolate, 34–41 µm long, 20–23 µm wide medially. Laterosternite IX with 1 seta. Phalapodeme 52–55 µm long; transverse sternapodeme indicated. Gonocoxite 84–95 µm long. Inferior volsella 48–52 µm long, 8 µm wide at base, 7 µm wide at apex, weakly curved with rounded apex, with microtrichia and 2–4 strong apical setae sitting on small tubercles, all setae simple and curved. Superior volsella ( Fig. 11 ) weakly sinuous, 20–23 µm long, 4–6 µm wide at base, 4–6 µm wide at apex, with microtrichia and 1–3 apical setae. Median volsella ( Fig. 12 ) 9 µm long, straight, tapering, without microtrichia and basal setae, with 2 apical setae sitting on small tubercles. Gonostylus 70–75 µm long, widest in apical 1/3, all setae hair-like. HR 1.19–1.27, HV 3.68.

Pupa (n = 1). Total length 2.72 mm. Exuviae light brown.

Cephalothorax ( Fig. 13 ). Frontal apotome and frontal setae not discernable. Thoracic horn ( Fig. 14 ) with 5 filaments, four of them single, the fifth split into two branches; main filament about 340 µm long with 2 minute spines; basal ring oval, about 8 µm in diameter. Scutum with field of few weak tubercles. Antepronotals apparently 2, median about 93 µm long, lateral 29 µm long. Precorneals 2, subequal, about 40 µm long. Dorsocentrals 4, Dc1 14 µm long, Dc2 and Dc4 lost, Dc3 25 µm long; Dc1 34 µm in front of Dc2, Dc2 137 µm in front of Dc3, Dc3 41 µm in front of Dc4.

Abdomen ( Figs 15–16 ). Tergite I with few weak spinules anteriolaterally; 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 with single posterior shagreen patch; tergite VIII with median and posterior shagreen patches connected; tergite IX bare. Tergite II with 223 µm long row of 55 hooks, each hook 4–9 µm long. Conjunctives III/IV and IV/V with 4 and 6 rows of spinules, respectively. Pedes spurii B weakly developed on segment II. Anal comb 23 µm long, consisting of 2 spurs.

Abdominal setation. Lateral setae on segments I–VIII as: 1, 3, 3, 3, 4, 4, 4, 4; posterior lateral seta on tergite IV and all lateral setae on tergites V–VIII taeniate, remaining setae hair-like. All tergites with 1 pair of O setae.

Anal lobe. With complete fringe of 22 taeniae on each side, longest about 550 µm long. Male genital sac overreaches anal lobe by 245 µm.

Female and larva. Unknown.

Distribution. Known from Amazonas and Mato Grosso, Brazil.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV BR p1 553 387 – – – – – – – – – p2 507 359 221 101 83 46 37 0.61 4.07 3.92 – p3 – – – – – – – – – – –

Figures

FIGURES 9 – 12. Nilothauma aripuanense sp. n., male. 9 — dorsal aspect of hypopygium. 10 — hypopygium with tergite IX and anal point removed, dorsal view left, ventral view right. 11 — superior volsella, dorsal view. 12 — median volsella, dorsal view.

FIGURES 13 – 16. Nilothauma aripuanense sp. n., pupa. 13 — thorax, lateral view. 14 — thoracic horn. 15 — tergites I – VII. tergite VIII and anal lobe.