Tanytarsus insignis, Dantas & Giłka, 2017

Dantas, Galileu P. S. & Giłka, Wojciech, 2017, New Tanytarsus van der Wulp from the Brazilian Amazonia indicate clues to intrageneric relations (Diptera: Chironomidae), Zootaxa 4294 (2), pp. 281-291 : 284-287

Tanytarsus insignis sp. nov.

( Figs 2 A–F, 4B)

Type material: Holotype, adult male: BRAZIL, Amazonas state, Puraquequara near Manaus (02°43'02"S / 59°54'04"W), 0 7 July 2015, Malaise trap, G.P.S. Dantas ( INPA).

Derivatio nominis. From Latin insignis (distinguished, remarkable).

Diagnosis. Anal tergite bands Y-shaped. Anal point strongly elongated, parallel-sided, bearing narrow crests. Superior volsella elongated, bent and narrowed at mid length, with long slender distal part, apically rounded.

Description. Adult male (n = 1).

Body size and proportions. Total length 3.92 mm. Wing length 1.83 mm. Total length/wing length 2.14. Wing length/length of profemur 1.56.

Colouration. Eyes black. Antenna, head capsule, palp, scutal vittae, postnotum and sternum light brown. Ground colour of thorax, scutellum and haltere brownish yellow. Fore leg: femur yellow, dark-brown at apex; tibia brown; ta1 light-brown, pale at base; ta2 pale, light-brown at apex; ta3-5 light-brown. Mid and hind legs: femora yellow, brown at apex; tibiae light-brown; ta1-5 brownish yellow, ta1 of mid leg with slightly darker apex. Wing membrane with pale brownish undertone. Abdomen brownish, TVI and TIX darker.

Head. Eyes bare, with well developed dorsomedian extensions. Antenna with 13 flagellomeres; ultimate flagellomere 754 µm long; AR 1.50. Frontal tubercles absent. Tentorium 272 µm long. Temporal setae 14 on each side. Clypeus with 39 setae. Lengths of palpomeres 1–5 (in µm): 40, 52, 145, 170, 285; third palpomere with 5 sensilla clavata subapically, 19 µm long.

Thorax. Ac 24, restricted to anterior region of scutum; Dc 11–13 on each side, uniserial; Pa 3–4 on each side; Scts 5. Scutum projected anteriorly, distinctly overreaching antepronotum.

Wing. Ellipse-shaped, as shown in Fig. 4 B. All veins and almost entire membrane below radial veins covered with macrotrichia (except for base of media and anal cells). Brachiolum with 1 seta. VR Cu 1.19.

Legs. Fore leg tibia with straight lanceolate spur 25 µm long. Tibial combs of mid and hind legs separated; spurs of mid leg unequal: one markedly bent, 45 µm long, second short and straight, 15 µm long; spurs of hind leg unequal: one larger, slightly bent, 58 µm long, second short and straight, 30 µm long. Basitarsus of mid leg without sensilla chaetica. Lengths and proportions of legs as in Table 2.

Hypopygium ( Fig. 2 ). Tergite IX covered with microtrichia on entire surface, with ca. 25 setae around base of anal point. Lateral teeth single-lobed. Anal tergite bands Y-shaped, fading at junction and at base of anal point. Anal point strongly elongated (38 µm), narrow (7 µm wide), parallel-sided, with slightly swollen round tip, anal crests long and narrow, spinulae absent ( Fig. 2 A, C). Superior volsella strongly elongated (55 µm), stout at base, bent and narrowed at mid length, with long slender distal part, apically rounded, bearing ca. 10 setae arranged as shown in Fig. 2 D; digitus ca. 50 µm long, curved and medially directed, parallel-sided, rounded apically ( Fig. 2 A, D). Stem of median volsella straight, ca. 30 µm long, 7 µm wide, slightly swollen at mid length, apically pointed, with 7–8 slender foliate and subulate lamellae ( Fig. 2 B, E). Inferior volsella ca. 100 µm long, club-shaped, narrow at base, with distinctly broadened head-like distal part bearing ca. 15 strong setae: 3 setae posteromedially directed, 11–12 anteromedially directed, incl. 6–7 setae arranged in row ventrally ( Fig. 2 B, F). Phallapodeme 134 µm long; transverse sternapodeme 61 µm long, with slight oral projections. Gonocoxite 145 µm long. Gonostylus 155 µm long, broadest at mid length, evenly tapering toward blunt apex. HR 0.93, HV 2.53.

Discussion. Trivinho-Strixino and Strixino (2004) described two distinctive species from the southeast of Brazil, Tanytarsus impar and T. magnus , peculiar in term of both the hypopygium structure and the body colouration. Adult males of the two species have the superior volsella more or less elongate, the digitus long and curved, the inferior volsella club-shaped and the anal point lacking spinulae. This set of characters was found in the male of Tanytarsus insignis as well, thus justifies the inclusion of the three relatives into the impar species group. The new species differs from its congeners by the strongly elongate anal point bearing narrow crests, the Y-shaped anal tergite bands and the elongate superior volsella—bent and narrowed at mid length (cf. Fig. 2 and Trivinho- Strixino & Strixino 2004: figs 2, 17).

Though intraspecific variations in the body colouration are usual in the majority of Tanytarsini adults, extraordinary (presumably constant) colour patterns are known from several Neotropical Tanytarsus species (e.g. Trivinho-Strixino et al. 2015: fig. 5a; see also the next species described below). The colouration of abdominal tergites as well as the leg colour band pattern found in males of the three species of the impar group are similar, thus we suggest to treat them as characters supplementing the group diagnosis. The darker (brown) distal abdominal tergites (beginning from the VI tergite towards back) stand out from the proximal (yellow) ones (cf. Trivinho-Strixino & Strixino 2004: figs 1, 15), with slight differences in this pigmentation pattern in Tanytarsus insignis (tergites VI and IX darker).

Ecological notes. The adult males of Tanytarsus insignis and T. insolens (see below) were collected with Malaise traps acting over a first-order stream, surrounded with a dense riparian forest, whose bed was predominantly sandy, with presence of clay.

Figures

FIGURE 2. Tanytarsus insignis sp. nov., male. A, B — hypopygium in dorsal (A) and ventral aspect (B); C — anal point; D — superior volsella and digitus; E — median volsella; F — inferior volsella (C – F magnified ca. 3 – 4 times relative to A and B).

FIGURE 4. Wing of male: Tanytarsus illustris sp. nov. (A), Tanytarsus insignis sp. nov. (B), Tanytarsus insolens sp. nov. (C).