Riethia epleri, Andersen & Malla, 2023

Andersen, Trond & Malla, Annui, 2023, A new species of Riethia Kieffer, 1917 from Zurqui, Costa Rica (Chironomidae, Chironominae, Pseudochironomini), Norwegian Journal of Entomology 70, pp. 29-33 : 30-33

Riethia epleri sp. n. ( Figures 1–6 )

Type material. Holotype ♂ adult (slide mounted), COSTA RICA: San José Province, Moravia, Zurqui de Moravia , creek river, 1600 m asl., 24 September 2012, light trap, project ZADBI, (slide no: ZADBI-39 , -84:00:57 10:02:58 #105053; INBIO) . Paratypes. 4♂♂ as holotype (slides no: ZADBI-43 , -84:00:57 10:02:58 #105056, 1♂ LACM; ZADBI-39 , -84:00:57 10:02:58 #105053, 1♂ LACM, 2♂♂ ZMBN) ; 2♂♂ as holotype except 21 September 2012 (slides no: ZADBI-33 , -84:00:57 10:02:58 #105048, LACM) ; 4♂♂ as holotype except 22 September 2012 (slides no: ZADBI-46 , -84:00:57 10:02:58 #105059, 3♂♂ LACM; ZADBI-41 , -84:00:57 10:02:58 #105054, 1♂ LACM) ; 1♂ as holotype except Aquatic emergence trap (slide no: ZADBI-58 , -84:00:57 10:02:58 #105071, LACM) ; 2♂♂ as holotype except 24 September–2 October 2012, Aquatic emergence trap (slides no: ZADBI-68 , -84:00:57 10:02:58 #105158, 1♂ LACM; ZADBI-99 , -84:00:57 10:02:58 #105153, 1♂ LACM) ; 1♂ as holotype except 19–26 April 2013, Malaise trap (slides no: ZADBI-673 , -84:00:57 10:02:58 #106619, ZMBN) .

Diagnostic characters. The new species can be distinguished from other Neotropical Riethia species by having a superior volsella that is bent nearly 90 o medially, apically straight, parallel-sided with bluntly rounded to triangular apex projecting mesad, basally with microtrichia, apically without microtrichia, with row of dorsal setae and 2 strong ventral setae; a bluntly subtriangular inferior volsella, with microtrichia, weak setae, and 9–11, 10 broad scales in double row along inner margin; and a median volsella consisting of two bluntly triangular tubercles, each with single seta.

Etymology. Named after John H. Epler, Florida, for his many contributions to chironomid taxonomy and for having sorted out the material of the new species.

Description. Adult male (n = 5–7). Total length 4.84–5.99, 4.95 mm. Wing length 2.20– 2.25, 2.22 mm. Total length / wing length 2.18– 2.29, 2.23. Wing length / length of profemur 2.38– 2.68, 2.52.

Coloration. Head and legs light brown, thorax brown with posterior part of scutum and postnotum dark brown, abdomen brown. Wing hyaline.

Antenna. Antennal Ratio (AR) = 1.02–1.21, 1.11. Terminal flagellomere 498–556, 519 µm long.

Head. Temporal setae 19–25, 22, bi- to triserial. Clypeus with 11–16, 14 setae. Tentorium 178–191, 185 µm long, 41–43, 42 µm wide. Stipes 158–189, 173 µm long, 8–14, 11 µm wide. Palpomere lengths (in µm): 51–57, 54; 70–78, 75; 170–178, 174; 133–164, 148; 219–262, 248. Third palpomere with 3–5 sensilla clavata subapically, longest about 20 µm long.

Thorax. Antepronotum with 2–4, 3 ventrolateral setae. Acrostichals 18–21, 19 in double row; dorsocentrals 8–11, 10 in single row; prealars 3–4, 4. Scutellum with 16–19, 18 setae in two rows.

Wing ( Figure 1 ). Wing Ratio (VR) 1.11–1.15, 1.13. Brachiolum with 1–2, 2 setae; R with 15–17, 16; R 2+3 with 12–16, 13; R 4+5 with 5–13, 9 setae; other veins and membrane bare. Squama with 9–14, 11 setae.

Legs. Spur of fore tibia 55–66, 59 µm long; spurs of mid tibia 76–83, 79 µm and 80–94, 84 µm long; spurs of hind tibia 90–95, 92 µm and 97–102, 99 µm long. Width at apex of fore tibia 54–62, 59 µm; of mid tibia 62–69, 66 µm; of hind tibia 66–73, 69 µm. Lengths and proportions of legs as in Table 1.

Hypopygium ( Figures 2–6 ). Tergite IX medially with straight to weakly concave posterior margin, with posteriolateral, rounded lobes fringed with long microtrichia; with 41–45, 43 setae. Laterosternite IX with 5–7, 6 setae. Phallapodeme 154–170, 162 µm long; including 35–47, 41 µm long, narrow, curved oral projection. Transverse sternapodeme arched, 80–96, 90 µm long. Gonocoxite 170–185, 176 µm long. Superior volsella bent nearly 90 o medially, basal part with microtrichia; apical part 72–80, 77 µm long, 11–14, 13 µm wide, straight, parallel-sided with bluntly rounded to triangular apex projecting mesad, apically without microtrichia and with row of dorsal setae and with 2 strong ventral setae. Inferior volsella bluntly subtriangular, 79–90, 86 µm long, 52–63, 58 µm wide medially, with microtrichia, weak setae, and 9–11, 10 broad scales in double row along inner margin. Median volsella consisting of two bluntly triangular tubercles, each with single seta, longest setae 43–49, 46 µm long. Gonostylus 144–154, 149 µm long. Hypopygium Ratio (HR) 1.13–1.23, 1.18. Hypopygium Value (HV) 3.34–3.52, 3.41.

Immatures and female. Larva, pupa, and female are unknown.

Distribution. The species is known only from a tropical cloud forest at Zurqui in Costa Rica, where it was collected at a creek at 1600 m altitude.

Acknowledgements. We are indebted to John H. Epler and Brian Brown for lending us the material from Zurqui.

Figures

FIGURE 1. Riethia epleri sp. n., male. Wing.

FIGURES 2–6. Riethia epleri sp. n., male.2. Hypopygium, dorsal view.3. Hypopygium with tergite IX removed, dorsal aspect to the left, ventral aspect to the right. 4. Superior volsella. 5. Inferior volsella. 6. Median volsella.