Stempellinella distincta, Ekrem, 2007

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1403-1404

Stempellinella distincta sp. n.

Type material

Holotype: „ ( UMSP) USA, WY: Buffalo , 0.5 mile Powder R. Pass, Canyon Ck., 9500 ft, 26 August 1967, D. Hansen.

Paratypes: USA: 7 „„ (4 UMSP, 2 JES, 1 VM) as holotype; 10 „„ (4 UMSP, 5 JES, 1 VM) WY, Buffalo, S. Fork of Clear Ck. , S. Fork Campground, 22 August 1967 , D. Hansen; 1 „ (VM) OR, Lincoln Co., 9 mile S. Toledo, Flynn Ck., 5–10 May 1962 .

Etymology

‘‘Distincta’’, Latin adjective meaning different, referring to the differently shaped and characteristic setiger of the superior volsella.

Diagnostic characters

Stempellinella distincta can be separated from other Stempellinella species by the following combination of characters: adult male with AR 0.7–0.9; anal point with numerous strong spinulae between well-developed anal crests; strong median setae on anal tergite; lateral anal tergite setae present; setiger of superior volsella long, narrow, strongly curved medially; median volsella 40–50 Mm long with microtrichose, palmate stem.

Description

Adult male (n 5 4, unless otherwise stated). Total length 1.5–1.7, 1.6 mm; wing length 1.11– 1.41, 1.29 mm.

Colour: head and thorax brown with somewhat darker scutal stripes, preepisternum, postnotum, eyes, and antennal pedicels. Eyes darker ventrally.

Head ( Figure 12A, B ): eyes without dorsomedian elongation; frontal tubercle ( Figure 12A ) large, conical, 15–20, 18 Mm long; antenna ( Figure 12B ) with 13 flagellomeres of which only 10 are easily discernible; AR (on 10 flagellomeres) 0.79–0.90, 0.84 (n 53); lengths of palpomeres (in Mm): 20; 25–30, 29; 70–90, 81; 85–100, 92 (n 53); 140–150 (n 52). Clypeus about 35 Mm long with 9–10 setae; tentorium ca 95 Mm long, 20 Mm wide; one to four inner verticals, none to two outer vertical, three postorbitals.

Thorax: scutal tubercle absent; acrostichals 10–13, 11; dorsocentrals 6–8, 7; humerals 0– 1; prealars 1; scutellars 6–7; halterals 5–6.

Wing ( Figure 12C ): cuneiform, 3.1–3.3, 3.2 times longer than broad; VR 1.48–1.53, 1.51 (n 53); wing setation as in Figure 12C .

Legs ( Figure 12D ): fore tibia with 15 Mm long spur; mid and hind tibiae with wellseparated, 10–12 Mm long tibial combs, one comb on each tibia with 25–30, 27 Mm long spur; tarsi without sensilla chaetica; pulvilli absent. Lengths and ratios of leg segments in Table III.

Hypopygium (n 55, Figure 12E, F ): anal tergite 98–110, 107 Mm long with transverse anal tergite band, four to seven, five strong median setae far from anal point base, frequently one or two small setae near base; lateral anal tergite seta present; anal point 40– 50, 45 Mm long, basally 13–15 Mm broad with well-developed crests, distally thin and pointed; 10–18, 13 strong spinulae between anal crests; small microtrichia-free areas present on each side of anal point base. Gonocoxite 75–88, 84 Mm long; gonostylus 53–62, 56 Mm long; HR 1.36–1.66, 1.50. Superior volsella long, narrow, setiger curved medially, four to six dorsal and two median setae, basomedian seta usually on small ventral tubercle, superior volsella otherwise bare; digitus absent but angled contour present ventrally on setiger; median volsella 35–45, 42 Mm long, posteriorly directed, palmate stem with long microtrichia, with simple 10 Mm long lamellae; inferior volsella 65–75, 70 Mm long, slightly club-shaped, with five distal setae, dorsal surface without microtrichia.

Adult female, pupa, and larva. Unknown.

Remarks

Stempellinella distincta is very similar to S. tamaseptima in the adult male, but can be separated by the long, differently shaped superior volsella. The species has been recorded only from creeks in Wyoming and Oregon, USA (see above).

Figures

Figure 12. Stempellinella distincta sp. n., male imago. (A) Frontal tubercles; (B) antennal flagellum; (C) wing; (D) fore, mid, and hind tibiae; (E) hypopygium; (F) superior, median, and inferior volsellae.