Tanytarsus curticornis Kieffer, 1911

Giłka, Wojciech & Paasivirta, Lauri, 2009, Evaluation of diagnostic characters of the Tanytarsus chinyensis group (Diptera: Chironomidae), with description of a new species from Lapland, Zootaxa 2197, pp. 31-42 : 38-40

Tanytarsus curticornis Kieffer, 1911

( Figs 2 , 10–14 , 20, 23, 26 )

Tanytarsus curticornis Kieffer, 1911: 52 ; Lindeberg 1963: 127; Reiss & Fittkau 1971: 100. Tanytarsus (Tanytarsus) curticornis Kieffer, 1911 : Edwards 1929: 415 (partim).

Material examined. FINLAND. Puruvesi, Kesälahti, 5 August 2002, 1 male, W. Giłka. Vesijärvi near Lahti, 11 July 2002, 1 male, W. Giłka. SWEDEN. Västerdalälven near Sälen, 1 July 2006, river and fish-ponds, 8 males, W. Giłka.

Diagnostic description. Adult male (measurements in Table).

Ground colour of thorax, scutellum, haltere, legs and abdomen yellowish green; antennal pedicel, tentorium, scutal stripes, postnotum and sternum yellowish green to pale brown; wing membrane pale, with C, M and radial veins somewhat darker. Frontal tubercles usually absent. Third palpomere shorter than fourth. Wing membrane under M3+4, Cu1 and An partially free of macrotrichia; 1/4 proximal section of R4+5, proximal half of Cu and neighbouring false veins bare ( Fig. 2 ). Gonostylus with slight narrowing in distal part or regularly tapering to slender apex. Anal tergite with single strong basilateral seta on each side. Median setae absent. Anal point armed 4–10 (usually 7 or 8) spinulae, with blunt, widely rounded or slightly cut apex ( Figs 10–14 ). Superior volsella with median margin transversally cut. Pear-shaped apical lobe of digitus roundish, broadly conical, stout in comparison with relatively small superior volsella ( Fig. 20 ). Median volsella very short, inner margin of coxite above median volsella more or less straight ( Fig. 23 ). Inferior volsella short, with broadly rounded apex ( Fig. 26 ).

Discussion. All the examined males of Tanytarsus curticornis have the lightly coloured, usually uniformly yellowish-green body, with slightly darker, pale brown tentorium, pedicel and thoracic sclerites. The colouration, however, should be treated with caution in diagnosing the species, particularly in comparison with freshly emerged specimens of Tanytarsus brundini (see diagnoses).

In a number of samples taken in Lapland, we also found a few specimens which may fit Lindeberg's (1963) description of the “Mutenianjoki population”. Our material collected from two distant sites near Tsarmi and Lemmenjoki (Inari distr.) includes pale, yellowish-green specimens with a hypopygial structure similar to that illustrated by Lindeberg (1963, fig. 6). They are undoubtedly close to Tanytarsus curticornis , but differ in having a long triangular and usually acute hypopygial anal point, bearing 4–8 spinulae placed in a row or dispersed at the base of the anal point. The specimens have a slender inferior volsella lacking an apical expansion, 2–3 median setae (which may occasionally be absent) as well as a reduced wing setation. Due to the variable nature of the diagnostic structures, an unambiguous specific diagnosis could not be formulated based on the few specimens examined. Several males were collected from a boggy area of spring brooks (helocrene) at both sites.

Based on pupal descriptions ( Bause 1913, Krüger 1945), the record of T. virens in Lapland ( Thienemann 1941), and his unpublished materials, Lindeberg (l.c.) suggested a close relationship between Tanytarsus curticornis and Tanytarsus virens Kieffer, 1909 . However, the systematic status of Tanytarsus virens is not certain. The species has apparently been described (merely included into a key) from adults reared by Thienemann from immatures sampled in the Heilenbecke reservoir in Westphalia ( Kieffer 1909). The type series is probably lost. A single pupal exuviae of the Thienemann’s sample, which may have been used for Bause’s (1913) description, is deposited in the Zoologische Staatssammlung Muenchen. Using Langton (1991), the pupa keys out to Tanytarsus debilis (Meigen, 1830) (Spies, pers. comm.), a member of the Tanytarsus verralli species group ( Reiss & Fittkau 1971).

Figures

FIGURES 1 – 3. Male wing. 1: Tanytarsus brundini, 2: T. curticornis, 3: T. salmelai sp. n.

FIGURES 5 – 18. Variability in hypopygial anal point. 5 – 9: Tanytarsus brundini, 10 – 14: T. curticornis, 15 – 18: T. salmelai sp. n.

FIGURES 19 – 27. Hypopygial volsellae. 19 – 21: superior volsella and digitus, 22 – 24: median volsella and inner margin of coxite, 25 – 27: inferior volsella. 19, 22, 25: Tanytarsus brundini; 20, 23, 26: T. curticornis; 21, 24, 27: T. salmelai sp. n.