Riethia ecuadoriensis, Andersen & Malla & Giłka, 2024

Andersen, Trond, Malla, Annui & Giłka, Wojciech, 2024, Two new species of Riethia Kieffer, 1917 from Chile and Ecuador (Chironomidae: Chironominae, Pseudochironomini), Zootaxa 5448 (4), pp. 499-507 : 503-504

Riethia ecuadoriensis sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:58F17D34-5F7A-47E1-8954-6BBF2FBDA93B

( Figs 3A–C , 4A–C )

Type material. Holotype adult male (slide mounted under five coverslips), ECUADOR, Carchi Province, Reserva ecológica El Ángel, LagUnas El Voladero , 0.691132°N 77.882543°W, 3.800 m a.s.l., 21.x.1990, leg. K. Böttger ( ZSM) . Paratypes, 21 adult males as holotype ( ZSM, ZMBN) .

Etymology. The epithet, ecuadoriensis , is used as an adjective and meaning “from Ecuador ” in reference to the country of origin of the holotype.

Diagnostic characters. Riethia ecuadoriensis is a dark brown species, with uniformly coloured abdomen, without bands, except for subrectangular pale brown area on tergite VII, and with scattered microtrichia dorsally on the superior volsella. For other key characters see the diagnosis for R. chilensis given above.

Description. Adult male (n = 5)

Body size and proportions. Total length 5.42–5.87, 5.65 mm. Wing length 3.30–3.53, 3.39 mm. Total length / wing length 1.59–1.75, 1.67. Wing length / length of profemur 2.72–2.90, 2.79.

Colouration. Head light brown with dark brown pedicel; thorax and legs brown ( Fig. 3B ); abdomen brown, tergite VII with subrectangular pale brown area in posterior 1/3 flanked by brown lateral areas ( Fig. 3C ). Wing hyaline ( Fig. 3A ).

Antenna. AR 1.49–1.59, 1.54. Terminal flagellomere 817–850, 835 µm long.

Head. Temporal setae 16–19, 18, bi- to tri-serial. Clypeus with 15–20, 17 setae. Tentorium 195–230, 210 µm long, 59–68, 64 µm wide. Stipes 174–209, 197 µm long, 12–16, 15 µm wide. Palpomere lengths (in µm): 52–68, 61; 88–100, 92; 152–168, 158; 216–236, 226; 260–300, 285. Third palpomere with 5–7, 6 sensilla clavata subapically, longest about 28 µm long.

Thorax. Antepronotum with 1–4, 2 ventrolateral setae. Acrostichals weak, apparently 1–2, 2; dorsocentrals 8–12, 10 in single row; prealars 3; supraalar 1. Scutellum with 7–11, 9 setae in single row.

Wing ( Fig. 3A ). VR 0.99–1.04, 1.02. Brachiolum with 2–3, 3 setae; R with 19–25, 23; R 1 with 11–15, 13; R 4+5 with 21–26, 24 setae; other veins and membrane bare. Squama with 14–17, 16 setae.

Legs. Spur of fore tibia 69–79, 74 µm long; spurs of mid tibia 64–79, 73 µm and 76–86, 81 µm long; spurs of hind tibia 75–86, 80 µm and 83–94, 89 µm long. Width at apex of fore tibia 58–68, 64 µm; of mid tibia 66–72, 70 µm; of hind tibia 70–79, 75 µm. Lengths and proportions of legs as in Table 2 .

Hypopygium ( Figs 4A–C ). Tergite IX with slightly convex posterior margin, with 48–63, 54 setae mainly in two to three rows along posterior margin. Laterosternite IX with 7–11, 9 setae. Phallapodeme 131–149, 140 µm long; with 35–51, 41 µm long, narrow, curved oral projection. Transverse sternapodeme straight, 51–68, 59 µm long, with weak oral projections. Gonocoxite 252–277, 259 µm long. Superior volsella stout, weakly curved, with narrowly triangular apex projecting medially to anteromedially, 76–83, 80 µm long, 32–37, 34 µm wide medially, with 6–7, 6 weak dorsal setae and scattered microtrichia. Inferior volsella strongly bent dorsally with bluntly subtriangular apical part, 58–66, 62 µm long, 41–46, 43 µm wide, with microtrichia, marginal setae, and 20–25, 22 broad flattened, apically fringed setae ( Fig. 4A 1 ) dorsally. Pseudovolsella consisting of bluntly triangular tubercle, with single, 52–58, 56 µm long, curved seta, with second curved setae at base. Gonostylus 200–212, 209 µm long. HR 1.19–1.35, 1.24. HV 2.41–2.81, 2.67.

Female and immature stages unknown.

Geographical distribution and bionomics. The species is known only from páramo grassland in the high Andes in northern Ecuador, where the males were resting on Espeltia sp. close to a lake.

Figures

FIGURE 1. Riethia chilensis sp. nov., male. A—wing; B—foreleg; C—abdomen.

FIGURE 3. Riethia ecuadoriensis sp. nov., male. A—wing; B—foreleg; C—abdomen.

FIGURE 4. Riethia ecuadoriensis sp. nov., male. A—hypopygium, dorsal view; drawn without broad, flattened, apically pectinate setae on inferior volsella; A1—broad, flattened, apically pectinate setae (magnified × 3.5 relative toA); B—hypopygium with tergite IX removed, dorsal aspect to the left, ventral aspect to the right; C—superior volsella, dorsal view.