Rheotanytarsus amaru, Dantas & Huamantinco Araujo & Hamada, 2020

Dantas, Galileu P. S., Huamantinco Araujo, Ana A. & Hamada, Neusa, 2020, A new species of Rheotanytarsus Thienemann & Bause (Diptera: Chironomidae) from Peruvian Andes, with updated key to South American species, Zootaxa 4722 (2), pp. 195-200 : 196-198

Rheotanytarsus amaru sp. nov.

( Fig. 1 A–E)

urn:lsid:zoobank.org:act:C0635FB5-CCC0-4D08-8ED7-26A7D67DE29E

Type material: Holotype, adult male: PERU, Cusco department, Calca province, Lamay district, Urubamba river , 13°21’20” S, 71°56’08” W, 17.viii.2014, leg. N. Hamada, M. Bobadilla, R. L. Ferreira-Keppler & J.M.C. Nascimento ( MHN-UNMSM) . Paratypes, 6 males, as holotype ( MHN-UNMSM) ; 3 males as holotype ( INPA) .

Etymology. In Inca mythology, “Amaru” (quechua) is a huge double-headed serpent that dwells underground, at the bottom of lakes and rivers. The Inca Empire was the largest in pre-Columbian America, the administrative, political and military center of the empire was in the city of Cusco, near the type locality of the new species. The name is to be treated as a noun in apposition.

Diagnosis. Wing length> 2 mm; spurs on mid and hind tibiae present; anal tergite bands V-shaped; anal point parallel-sided; superior volsella oval, apically tapered; stem of median volsella curved, swollen and rounded at apex, bearing a brush of setiform lamellae not fused into a plate; median and superior volsella about the same size; gonostylus broadest subbasally, evenly tapering toward apex.

Description:

Adult male (n = 10). Body size and proportions. Total length 3.45–3.52 mm. Wing length 2.04–2.11 mm. Total length/wing length 1.67–1.70. Wing length/length of profemur 2.33–2.38.

Coloration. Eyes black. Head capsule and pedicel dark brown; antennal flagellum and palp brown. Thorax dark brown. All legs brown. Wing membrane with pale brownish undertone. Abdomen light brown.

Head ( Fig. 1A ). Eyes bare, with well-developed dorsomedian extensions. Antenna with 13 flagellomeres; ultimate flagellomere 485–492 μm long; AR 0.97–0.0.99. Frontal tubercles absent. Tentorium 150–160 μm long, heavily sclerotized. Temporal setae 8–11 on each side. Clypeus with 24–28 setae. Lengths of palpomeres 1–5 (in μm): 43–55, 42–52, 130–141, 130–132, 215–232; third palpomere with 1 sensillum clavatum subapically, 14–17 μm long. Fifth palpomere/ third palpomere ratio 1.65–1.70.

Thorax ( Fig. 1B ). Ac 22–24, restricted to anterior region of scutum; Dc 11–13 on each side, uniserial; Pa 1 on each side; Scts 7–9. Scutum projected anteriorly, distinctly overreaching antepronotum.

Wing ( Fig. 1C ). VRCu 1.35–1.43. Membrane covered with macrotrichia. Brachiolum with 1 seta, C with about 360 setae, R with about 20, R 1 with about 30, R 4+5 with about 60, M 1+2 with about 65, M 3+4 with about 45, Cu with about 25, Cu 1 with about 25 and An with about 40 setae, remaining veins bare.

Legs. Fore leg tibia with a sinuous spur 25–27 μm long. Tibial combs of mid and hind legs separated; spurs of mid leg equal, markedly bent at apex, about 22–23 μm long; spurs of hind leg equal: slightly bent at apex, 25–26 μm long. Lengths and proportions of legs as in Table 1 .

Hypopygium ( Fig. 1 D–E) Anal tergite with open, V-shaped bands. Posterior margin of tergite IX with about 10–13 setae. Anal point 48–52 μm long, 12–14 μm wide, parallel-sided; crest well developed and V-shaped with 2–5 median setae ( Fig. 1D ). Superior volsella 45–50 μm long, oval, apically tapered, with 6–7 dorsal and 2–3 marginal setae arranged as shown in Figs. 1 D–E. Stem of median volsella curved, 28–30 μm long, 5–6, 8–10 and 12–14 μm wide at base, middle and apex, respectively, swollen and rounded at apex, bearing a brush of setiform lamellae not fused into a plate ( Fig. 1E ). Inferior volsella 80–85 μm long, subcylindrical, bearing about 12–15 apical/subapical bristles; internal margin covered with microtrichia ( Fig. 1E ). Phallapodeme 80–90 μm long; transverse sternapo- deme 47–54 μm long, without distinct oral projections. Gonocoxite 132–150 μm long. Gonostylus 138–153 μm long, slightly arched, broadest subbasally, evenly tapering toward blunt apex. HR 0.95–0.98, HV 2.25–2.45.

Female and immatures. Unknown.

Distribution and ecological notes. The new species is known only for the type locality in the Peruvian Andes ( Fig. 2 ). The adults of Rheotanytarsus amaru sp. n. were collected next to a sand bottom river 6 m in width, with low temperature (about 15 °C) at about 3.000 m above s.l.

Figures

FIGURE 1. Rheotanytarsus amaru sp. n., Adult male:A. Head, in frontal view. B. Thorax, in lateral view. C. Wing. D. Hypopygium, in dorsal view. E. Hypopygium in dorsal view, with tergite IX removed.

FIGURE 2. Distribution of Rheotanytarsus Thienemann & Bause species in South America.