Riethia chilensis, 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 : 500-503

Riethia chilensis sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:6FB58B1E-775B-4B10-8628-51E06C8D5675

( Figs 1A–C , 2A–C )

Type material. Holotype adult male (slide mounted under five coverslips), CHILE, Los Rios Region, Valdivia Province, Panguipulli, El Desague , Lago Riñihue , Limnological field station, 39.774388°S 72.453394°W, 115 m a.s.l., 5.xi.1969, leg. F. Reiss ( ZSM) . Paratypes, 58 adult males as holotype ( ZSM, ZMBN) .

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

Diagnostic characters. Riethia chilensis differs from its close relative, R.truncatocaudata , by uniformly coloured legs, without bands, and curved, stout superior volsellae without microtrichia dorsally. A light brown abdomen, with darker anterior bands on the tergites, and a superior volsella without microtrichia are the characters that separate R. chilensis from the second new species described here (see below). Both new species + R. truncatocaudata can be separated from all other Riethia by having the inferior volsella strongly bent dorsally, with apical part subtriangular and dorsally covered with broad, flattened, apically fringed setae. See also the diagnosis for the second species.

Description. Adult male (n = 5)

Body size and proportions. Total length 5.21–5.71, 5.44 mm. Wing length 3.03–3.23, 3.09 mm. Total length / wing length 1.70–1.88, 1.76. Wing length / length of profemur 2.30–2.47, 2.35.

Colouration. Head pale brown with brown pedicel; thorax brown with pale brown vitae, scutellum, and posterior part of preepisternum; legs brown without darker bands ( Fig. 1B ); abdominal tergites brown in anterior ¼, light brown in posterior ¾ ( Fig. 1C ). Wing hyaline ( Fig. 1A ).

Antenna. AR 1.78–2.04, 1.91. Terminal flagellomere 760–920, 846 µm long.

Head. Temporal setae 31–36, 34, bi- to tri-serial. Clypeus with 18–22, 20 setae. Tentorium 193–221, 205 µm long, 57–66, 61 µm wide. Stipes 199–221, 209 µm long, 12–16, 14 µm wide. Palpomere lengths (in µm): 52–64, 58; 92–104, 97; 164–200, 181; 228–252, 237; 256–332, 289. Third palpomere with 4–7, 5 sensilla clavata subapically, longest about 29 µm long.

Thorax. Antepronotum with 8–12, 9 ventrolateral setae. Acrostichals strong, 9–16, 12, in double row; dorsocentrals 11–17, 14 in single row; prealars 3–5, 4; supraalar 1. Scutellum with 14–16, 15 setae in partly double row.

Wing ( Fig. 1A ). VR 1.06–1.12, 1.08. Brachiolum with 3 setae; R with 23–31, 28; R 1 with 19–24, 21; R 4+5 with 32–39, 36 setae; other veins and membrane bare. Squama with 10–15, 13 setae.

Legs. Spur of fore tibia 76–86, 81 µm long; spurs of mid tibia 58–69, 62 µm and 75–94, 82 µm long; spurs of hind tibia 72–88, 79 µm and 89–115, 99 µm long. Width at apex of fore tibia 75–94, 82 µm; of mid tibia 63–75, 69 µm; of hind tibia 72–79, 76 µm. Lengths and proportions of legs as in Table 1 .

Hypopygium ( Figs 2A–C ). Tergite IX with straight posterior margin, with 17–27, 23 setae medially and 34–51, 42 setae in two to three rows along posterior margin. Laterosternite IX with 6–9, 8 setae. Phallapodeme 154–186, 166 µm long; with 41–58, 47 µm long, narrow, curved oral projection. Transverse sternapodeme straight, 69– 97, 79 µm long, with comparatively long oral projections. Gonocoxite 242–275, 257 µm long. Superior volsella stout, curved, with long, narrowly triangular apex projecting anteromedially, 80–89, 86 µm long, 23–32, 26 µm wide medially, with 5 weak dorsal setae, without microtrichia. Inferior volsella strongly bent dorsally with bluntly subtriangular apical part, 54–69, 60 µm long, 37–44, 40 µm wide, with microtrichia, marginal setae, and 29–36, 32 broad flattened, apically fringed setae ( Fig. 2A 1 ) dorsally. Pseudovolsella consisting of low, bluntly triangular tubercle, with 2–3, 3 curved setae, longest seta 48–59, 55 µm long. Gonostylus 176–209, 194 µm long. HR 1.16– 1.56, 1.33. HV 2.74–2.96, 2.80.

Female and immature stages unknown.

Distribution. The species was collected resting on bushes and other vegetation near a lakeshore in southern Chile.

Figures

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

FIGURE 2. Riethia chilensis sp. nov., male. A—hypopygium, dorsal view; drawn without broad, flattened, apically pectinate setae on inferior volsella; A1—broad, flattened, apically pectinate setae (magnified × 4 relative to A); B—hypopygium with tergite IX removed, dorsal aspect to the left, ventral aspect to the right; C—superior volsella, dorsal view.