Tanytarsus costarica, Reis & Gil-Azevedo & Ferreira-Keppler, 2021

Reis, Patricia Do Rosario, Gil-Azevedo, Leonardo H. & Ferreira-Keppler, Ruth L., 2021, Two new species of Tanytarsus van der Wulp (Diptera: Chironomidae) from Costa Rica, Zootaxa 4966 (1), pp. 84-90 : 87-89

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Tanytarsus costarica

sp. nov.

Tanytarsus costarica sp. nov.

( Figs. 2A–C View FIGURE 2 , 3B View FIGURE 3 )

Type material. Holotype: adult male, Costa Rica, Prov. San José, Moravia, Zurquí de Moravia (10°02’58” N – 84°00’57” W), Creek 1 north. 1600 m. Canopy Malaise trap. 12–19.iv.2013 (INBIOCRI-COSTA RICA). GoogleMaps

Etymology. Named after the country where the species was found. Noun in apposition.

Diagnosis. Tanytarsus costarica can be separated from other species of the genus by the following combination of characters: head without frontal tubercles; Y-shaped anal tergite bands; anal point elongated, wide, divided into three portions, with two pairs of long bars; superior volsella with posteromedian lobe strongly produced; digitus finger-like; median volsella with simple lamellar setae mounted apically and 4 regular setae.

Description. Adult male (n=1). Small, total length 2.00 mm. Wing length 1.26 mm.

Colouration. Head yellowish-brown; flagellum and maxillary palp pale brown. Thorax and legs yellowish. Abdomen yellowish.

Head. Eyes bare, without dorsomedial extension. Frontal tubercles absent. Temporal setae 5+5. Antenna with 13 flagellomeres, 680 µm long. AR. 0.38. Length of palpomeres 2–5 (in µm): 25, 50, 90, 100.

Thorax. Ac 5; Pa 1; Scts 2. Halteres with 6 setae on both. Dorsocentral setae (Dc) not observed.

Wing ( Fig. 3B View FIGURE 3 ). Width 0.39 mm. VR 1.26. Sc, M, and RM bare, remaining wing veins and cells with setae. Brachiolum with one seta.

Legs. Foreleg bearing single tibial spur, 27.5 μm long. Mid leg tibia bearing two spurs, 17.5 μm and 27.5 μm long, and two separated combs. Hind leg tibia bearing two spurs, 17.5 μm and 30 μm long, and two separated combs. Lengths of leg segments and leg ratios as in Table 2 View TABLE 2 .

Hypopygium ( Figs. 2A–C View FIGURE 2 ). Tergite IX 169 μm long, with 2 distal setae. Y-shaped anal tergite bands “fused” on median part of tergite and reaching anal point, about 24 μm long. Anal point elongated (40 µm long), wide (17 µm width), divided into three very distinct portions (Fig. A, C), lateral margin with 2 pairs of setae in distal part; AnPR 2.35. Two pairs of anal point bars elongated (28 μm long), each bar tip split into two apices and reaching beyond apex of anal point; AnPBR 0.86. Superior volsella subrectangular, with 5 setae on dorsal surface, 3 setae on anteromedian margin (2 dorsal, 1 ventral), posteromedian corner and strongly projecting; digitus 13 µm long, pointed, finger-like, extending beyond margin of superior volsella. Stem of median volsella short, about 7 μm long, with simple lamellar setae and 4 regular setae. Inferior volsella ca. 61 μm long. Gonocoxite 67 μm long. Gonostylus 68 μm long, broader at mid-length, rounded tip. HR 0.99.

Remarks: The superior volsella of T. costarica sp. nov. is superficially similar to those of T. canine , T. comunis and T. mulleri but has a slightly more elongated posteromedian corner. The digitus, on the other hand, is distinct from these species, since it exceeds the lateral margin of the superior volsella, while in the above mentioned three species, the digit does not exceed the superior volsella. However, the best diagnostic character for the male of T. costarica is the anal point, which is distinctly trifid, with the lateral portions showing a pointed tip and the thumblike middle portion, a design unique among the species of the Tanytarsus ortoni group.

Distribution and ecological notes. T. costarica was also collected from the same study site and with the same type of trap as T. briani (Zurquí de Moravia, Costa Rica), about 1,600 meters above sea level.