Nilothauma matogrossense, 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 : 28-31

Nilothauma matogrossense sp. n.

( Figs 41–48 )

Type material. Holotype male with pupal exuviae, BRAZIL: Mato Grosso: Serra dos Parecis, Pensão Alemã, 10–11.x.1965, drift net, E. J. Fittkau ( ZSM).

Diagnostic characters. The single, dorsal lobe on tergite IX with strong, simple setae combined with a narrow, parallel-sided anal point and a long, narrow L-shaped superior volsella with single apical seta will separate the male of N. matogrossense from all other Nilothauma species. The pupa can be separated from other known Neotropical pupae by having a thoracic horn with 5 branches and the anterior and posterior shagreen patches on tergite VIII completely fused.

Etymology. Named after Mato Grosso State.

Male (n = 1–2). Total length 2.68 mm. Wing length 1.29 mm. Total length / wing length 2.08. Wing length / length of profemur 2.50.

Coloration. Thorax coloration not discernible; legs and antenna yellowish brown.

Head. AR 0.32–0.42. Thirteenth flagellomere 184–216 µm long. Temporal setae 3 in single row. Frontal tubercles apparently absent. Clypeus with 8–9 setae. Tentorium 95 µm long, 16 µm wide. Stipes not measurable. Palp segment lengths (in µm): 11–23, 18–25, 54–70, 95–100, 91–125. Third palpomere with 2 sensilla clavata subapically, longest 11–12 µm long. Fifth palpomere / third palpomere 1.67–1.77.

Thorax. Uncleared, setae not discernible.

Wing. VR 1.43. Brachiolum with 1 seta, R with 8 setae, R1 with 4 setae, R4+5 with 2 setae apically, remaining veins bare.

Legs. Spur of foretibia 37 µm long including 16 µm long scale. Midtibia with 1 spur, 27 µm long; hind tibia with 2 spurs, 36 µm and 16 µm long. Combs of midtibia 16 µm long, of hind tibia 20 µm long. Width at apex of foretibia 34 µm, of midtibia 36 µm, of hind tibia 36 µm. Lengths and proportions of legs as in Table 9.

Abdomen. Tergites with few setae. Segment VIII long, subtriangular, widest medially, weakly tapering anteriorly.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV BR p1 516 414 – – – – – – – – – p2 507 378 245 101 83 59 37 0.64 4.02 3.62 4.5 p3 589 608 – – – – – – – – – Hypopygium ( Figs 41–42 ). Tergite IX with broadly triangular posterior margin, with 4 weak marginal setae to each side of base of anal point; with single, median dorsal lobe, with about 45 strong setae. Anal point parallel-sided, 41–45 µm long, 7–9 µm wide at base, 7 µm wide at apex. Laterosternite IX with 1 seta. Phalapodeme 52 µm long; transverse sternapodeme indicated. Gonocoxite 73–77 µm long. Inferior volsella 57 µm long, 8 µm wide at base, 7 µm wide at apex, weakly curved with rounded apex, with microtrichia and 3–4 strong apical setae sitting on small tubercles, all setae simple and curved. Superior volsella ( Fig. 43 ) Lshaped, 27–36 µm long, 4–6 µm wide at base, 3–4 µm wide at apex, without microtrichia, with single apical seta. Median volsella ( Fig. 44 ) straight, tapering, 12–14 µm long, without microtrichia and basal setae, with 2 apical setae sitting on small tubercles. Gonostylus 125–134 µm long, widest in apical 1/3, all setae hair-like.

Pupa (n = 1). Total length 3.03 mm. Exuviae light brown.

Cephalothorax ( Fig. 45 ). Frontal apotome smooth, frontal setae 58 µm long. Thoracic horn ( Fig. 46 ) with 5 filaments; main filament 514 µm long with several minute spines; basal ring oval, 7 µm of diameter. Scutum with field of few weak tubercles. Antepronotals apparently 2, median about 166 µm long, lateral not measurable. Precorneals 2, subequal, about 20 µm long. Dorsocentrals 4, Dc1 11 µm long, Dc2 lost, Dc3 16 µm long, Dc4 7 µm long; Dc1 43 µm in front of Dc2, Dc2 113 µm in front of Dc3, Dc3 27 µm in front of Dc4.

Abdomen ( Figs 47–48 ). Tergite I with few weak spinules posteriomedially; 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 anterior and posterior shagreen patches connected by narrow band of fine shagreen; tergite VIII with median and posterior shagreen patches broadly connected; tergite IX bare. Tergite II with 188 µm long row of 44 hooks, each hook 6–9 µm long. Conjunctive III/IV with 4 rows of spinules; conjunctive IV/V with 1 row of weak spinules. Pedes spurii B weakly developed on segment II. Anal comb 25 µm long, consisting of 2–3 spurs.

Abdominal setation. Lateral setae on segments I–VIII as: 0, 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 24 taeniae on each side, longest about 450 µm long. Male genital sac overreaches anal lobe by 210 µm.

Female and larva. Unknown.

Distribution. Known only from the type locality in Mato Grosso, Brazil.

Figures

FIGURES 41 – 44. Nilothauma matogrossense sp. n., male. 41 — dorsal aspect of hypopygium. 42 — hypopygium with tergite IX and anal point removed, dorsal view left, ventral view right. 43 — superior volsella, dorsal view. 44 — median volsella, dorsal view.

FIGURES 45 – 48. Nilothauma matogrossense sp. n., pupa. 45 — thorax, lateral view. 46 — thoracic horn. 47 — tergites I – VII. 48 — tergite VIII and anal lobe.