Stempellinella brevis (Edwards)

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1383-1388

Stempellinella brevis (Edwards)

Tanytarsus (Stempellina) brevis Edwards 1929, p 420 . Lectotype „ ( BMNH 236365 ) Scotland: Arran island , Sannox, 26–28 May 1919, F. W. Edwards [examined] . Paralectotypes (22) in BMNH [not examined] . Lectotype here designated.

Stempellina brevis (Edwards) . Goetghebuer (1937 –54) taxonomy, keys.

Stempellinella brevis (Edwards) . Brundin (1948, 1949), Dittmar (1955) taxonomy, ecology, and distribution.

Additional material examined

Finland: 4 „„ ( ZMUH) Lake Puruvesi, 18 June 1960, 4 July 1961, 17 July 1957, B. Lindeberg; 1 „ ( ZMUH) Tampere, Särkijärvi, 18 July 1982, J. Tuiskunen; 4 „„ ( ZSM) Keitela, 10 August 1967, F. Reiss. Germany ( ZSM): 3 L Hessen, Schlitz, Breitenbach, 25 May 1988, B. Wolf; 2 L as previous except 30 August 1988, U. Nolte; 1 „ as previous, except emergence house, 20 July 1971, M. Siebert; 18 „„, 7♀♀, 1 P „, 3 P(„), 5 P(♀), 22 Pex, Hessen, Fulda, Wasserkuppe, 3 May 1953, 4 May 1953, 7 May 1953, 26 June 1953, 1 July 1953, 13 August 1953, 3 October 1953, E. J. Fittkau; 2 L Bavaria, München, Pullach, Convenz-Bach, 20 May 1983, E. G. Burmeister; 1 P „, 2 Pex Baden-Württemberg, Schwarzwald, Windgfällweiher at Altglashütten, 966 m a.s.l., 6 June 1953, 27 June 1953, W. Wülker; 5 „„, 1♀, 2 P(„), 4 Pex, 1 L, Nordrhein-Westfalen, Sauerland, 1952, H. Dittmar. Norway: 1 P(„) ( PHL) Buskerud, Hol, Holvaervatnet, 1181 m a.s.l., 29 July 1993, P. H. Langton; 1 „ ( ZSM) Oppland, Øystre Sildre, Øvre Heimdalsvatn, 14 July 1972, J. Brittain and A. Lillehammer; 1 „ ( ZSM) Oppland, Lom, Lom, and Øye, 18 July 1958, J. Clastrier; ZMBN: 1 „, MØre og Romsdal, Volda, LitlabØvatn, 26 July 1986, Ø. A. Schnell; 1 „, Rogaland, Bjerkreim, river at Tengs camping, 25 May 1988, Ø. A. Schnell; 1 „, Hordaland, Øygarden, Storavatn at tunnel, 25 May 1987, at light, T. Andersen; 2 Pex, Hordaland, Bergen, Frotveitvatn, 25 August 1987, drift, H. Saegrov and Ø. A. Schnell; 2 P(„), Hordaland, River Ekse, 26 July 1989, drift, Ø. A. Schnell; 1 P(„), 1 Pex, Sogn and Fjordane, Vik, Selhamarvatn, 2 August 1992, 10 August 1992, Ø. A. Schnell; 2 „„, Sogn og Fjordane, Aurland, Stream between Aurlandsvatnet and NesbØvatnet, 21 July 2001, T. Ekrem; 1 „ Hordaland, Kvam, TØrrvikvatn, 24 July 2001, G. A. Halvorsen; 1 „ Aust Agder, Bykle, Otra at GlitbjØrg, 29 June 2001, T. Ekrem; 2 L, Aust Agder, Åmli, Skjeggedalsåna, station 1, 6 October 1998, G. A. Halvorsen; LP („), Vest Agder, Vågsbygd, Kjosbekken at Storevann; 1 „ Vest Agder, SØgne, SØgneelva at SØgne Gamle Kirke, 4 July 2001, T. Ekrem; VM: 14 „„ Nord TrØndelag, HØylandet, Skiftesåa, 18 June 1986, 15 August 1968, 9 July 1988, 2 July 1988, 25 June 1988, 23 June 1987, 1 July 1987, 21 August 1988, 25 June 1986, 1 July 1986, 8 August 1986, 18 June 1986, 25 June 1988, 17 July 1988, K. Aagaard; 2 „„ Oppland, Øystre Sildre, Øvre Heimdalsvatn, 29 July 1972, J. Brittain and A. Lillehammer. Portugal ( ZSM): 1 „, Ribeira d’Alge, Campel (Figuero dos Vinhos), 21 May 1982, L. Whytton da Terra; 1 Pex, Reservoir Vita de Ponte, 17 April 1984, drift, E. J. Fittkau. Scotland: 1 P(„) ( PHL) Loch Ard., 17 August 1983, P. H. Langton. Spain: 1 „ ( ZSM) Caceres Rivera de Gata, at Villas buenas, 400 m a.s.l., 9–10 July 1987, W. Schacht. Sweden ( ZSM): 2 „„ Jämtland, Stora Blåsjön, L. Brundin.

Diagnostic characters

Stempellinella brevis can be separated from other Stempellinella species by the following combination of characters. Adult male with wing length ca 1.3 mm, 3.2 times longer than broad; AR about 0.8; frontal tubercles large, conical; anal point with several (4–10) small spinulae between u-shaped crests; few (4–7) median tergite setae of which a few small sometimes are placed close to anal point; median volsella without microtrichiae, with fan of simple lamellae. Adult female with AR 0.26–0.32; vaginal floor large, covering more than half of vagina ventrally; spermathecal ducts longer than notum and rami combined; rami as long as notum; diameter of seminal capsules lower than length of notum; coxosternapodeme without anterolateral lobe. Pupa with moderately developed, conical cephalic tubercles; thoracic horn long and thin with numerous small chaetae scattered on middle one-third; posterior precorneal somewhat shorter than anterior and posterior precorneals; thorax with scattered sculpturing anteriorly; anterior dorsocentrals of same length as posterior dorsocentrals; point patches on tergite II small, starting at level of seta D5; anal lobe with 15–16 taeniae. Larva with moderate (ca 24 Mm long), digitiform spur on antennal pedestal; AR 0.77–0.87; S3 split in three or four branches; distal Lauterborn organ pedicel twice as long as basal Lauterborn organ pedicel.

Redescription

Adult male (n 5 5, unless otherwise stated). Total length 1.6–2.0, 1.7 mm; wing length 1.13– 1.44, 1.30 mm.

Colour: head pale brown with dark pedicels and eyes; thorax with pale brown ground colour, dark brown scutal stripes, brown postnotum, preepisternum, and median anepisternum, scutellum pale, halteres pale; abdomen pale brown.

Head ( Figure 5A, B ): eyes without dorsomedian elongation; frontal tubercle large, conical, 11–15, 14 Mm long; antenna ( Figure 5C ) with 13 flagellomeres of which only 10 are easily discernible; AR (on 10 flagellomeres) 0.80–0.91, 0.84; lengths of palpomeres (in Mm): 21–27, 24; 25–30, 29; 65–75, 72; 82–102, 92; 122–150, 134. Clypeus about 50 Mm long with 10–14, 11 setae; tentorium ca 94 Mm long, 16 Mm wide; three inner verticals, three or four outer verticals, two or three postorbitals.

Thorax: scutal tubercle absent; acrostichals 13–17, 15; dorsocentrals 6–9, 7; humerals 1– 3, 2; prealars 1–2; scutellars 6–11, 9; halterals 5–9, 7.

Wing ( Figure 5C ): cuneiform, 3.0–3.3, 3.2 times longer than broad; VR 1.48–1.56, 1.51; wing setation as in Figure 5C .

Legs ( Figure 5D ): fore tibia with 11–19, 15 Mm long spur; mid and hind tibiae with wellseparated, 11–14, 12 Mm long combs, one mid tibial comb with 25–36, 31 Mm long spur, one hind tibial comb with 29–36, 33 Mm long spur; mid tarsus 1 without sensilla chaetica; pulvilli absent. Lengths and ratios of leg segments in Table III.

Hypopygium ( Figure 5E, F ): anal tergite 111–129, 118 Mm long with transverse anal tergite band; four to seven median tergite setae, sometimes some smaller setae placed close to anal point base, one lateral seta, 24–30, 27 apical setae; anal point 48–51, 50 Mm long, basally 8–12, 10 Mm broad with well-developed crests, anal point distally thin and pointed; 4–10, 7 small spinulae between crests on anal point; small microtrichia-free areas present at base of anal point. Gonocoxite 75–96, 85 Mm long; gonostylus 52–66, 58 Mm long; HR 1.44–1.48, 1.46. Superior volsella ( Figure 5F ) oval with posteromedially directed apical point, with five or six dorsal and two median setae on setiger, superior volsella otherwise bare; digitus absent; median volsella 27–38, 32 Mm long, posteromedially directed, stem simple, bare, with fan of simple 22–27, 24 Mm long lamellae; inferior volsella ca 65 Mm long, club-shaped, with several distal setae, dorsal surface without microtrichia, basal wart absent.

Adult female (n 5 5, unless otherwise stated). Total length 1.1–1.3, 1.2 (n 54) mm; wing length 1.08–1.18, 1.14 mm.

Colour: pale yellow-green.

Head: as male, except cephalic tubercles 6–10, 7 Mm long; antenna ( Figure 5G ) with five flagellomeres, ultimate flagellomere 57–72, 62 Mm long, AR 0.26–0.33, 0.30; lengths of palpomeres (in Mm): 21–24, 22; 24–30, 27; 57–67, 61; 75–87, 83; 110–129, 119. Clypeus with 9–10 setae.

Thorax: acrostichals 15–18, 16; dorsocentrals 6–8, 7; humerals 3–6, 4; prealars 1; scutellars 6–7; halterals 5–6.

Wing: as male, except 2.8–2.9 times longer than broad. VR 1.43–1.48, 1.46.

Legs: as male.

Genitalia ( Figure 5H ): tergite IX semicircular, 36–54, 43 Mm long; sternite VIII with 20 (n 52) setae, of which two are placed on vaginal floor; vaginal floor large, covering half of vaginal opening ventrally; gonapophysis VIII single lobe with long posteromedially directed microtrichia; gonocoxapodeme slightly curved; coxosternapodeme well developed with obvious posterior lobe. Notum including rami 105–120, 115 (n 54) Mm long, notum alone ca 60 Mm long. Seminal capsules ovoid, diameter 34–57, 50 Mm with ca 165 Mm long spermathecal ducts. Postgenital plate triangular. Cercus 45 Mm long.

Pupa (n 5 5, unless otherwise stated). Total length 2.4–2.8, 2.6 mm; abdomen 1.9–2.3, 2.1 mm long. Colour of pupal exuviae pale brown with darker lateral margins on abdominal segments VII – VIII and anal lobe.

Cephalothorax ( Figure 6A, B ): cephalic tubercle moderately developed, broad conical, 14–30, 22 Mm long; frontal setae taeniate, 110–165, 133 Mm long; pedicel sheath tubercle absent. Thoracic horn 360–432, 386 Mm long, 18–21, 20 Mm wide with 6–12, 8 Mm long chaetae scattered on middle one-third; precorneals taeniate, arranged in almost a row on obvious mound, anterior and median setae ca 200 Mm long, posterior seta ca 150 Mm long, all three placed at about equal distance from each other; median antepronotal taeniate, two lateral antepronotals: one taeniate, one sensillum basiconicum; two pairs of fine dorsocentrals, anterior pair 33–36 Mm and 20–21 Mm long, posterior pair 30 Mm and 20– 21 Mm long. Area of fine sculpturing anteriorly on thorax, a few stronger granules present along median suture line. Prealar tubercle well developed, wide; nose of wing sheath well developed.

Abdomen ( Figure 6C ): TII with small triangular posteromedian point patches which start slightly anteriorly to seta D 5; hook row 75–90, 81 Mm wide with 36–46, 37 hooks. TIII – VI with large, p -shaped point patches; TVII –IX with anterolateral patches of shagreen. Segment II with pedes spurii B; segment IV with pedes spurii A. Segment II with 2 D, 2 V, 3 L setae; segment III with 3 D, 2 V, 3 L setae; segment IV with 3 D, 3 V, 2–3 simple and 0–1 semi-taeniate L setae; segment V with 3 D, 3 V, 3 taeniate L setae; segment VI – VII with 3 D, 3 V, 4 taeniate L setae, segment VIII with 1 D, 1 semi-taeniate V, 3 taeniate L setae; segment IX with 1 D seta on anal lobe, 15–16 taeniate setae in anal fringe. One pair of O-setae present anteriorly on tergites II – VIII and anterolaterally on sternites II – VIII. Pleura III – V with small field of weak shagreen. Posterolateral spur on segment VIII well developed.

Larva (n 5 5, unless otherwise stated). Total length 2.6–2.8, 2.7 (n 53) mm long, case ca 3.2 mm long. Head capsule brown, somewhat darker postoccipital rim and teeth on mandible and mentum. Live specimens yellow.

Head ( Figure 6D–I ): AR 0.77–0.87, 0.83; antennal pedestal 75 Mm long with welldeveloped, 23–30, 25 Mm digitiform spur; antenna ( Figure 6D ) with all segments well sclerotized, segment lengths (in Mm): 60–72, 65; 45–54, 49; 12–15, 13; 11–12; 4–6, 5; segment 3 inserted subapically on segment 2; AAR 1.14–1.25, 1.19 (n 54). Antennal seta placed at base just above ring organ; antennal blade 100–120, 107 Mm long, pale, reaching well beyond tip of distal Lauterborn organ; peg of antennal segment 2 placed subapically on segment. Lauterborn organs large, bulbous, 16–21, 18 Mm long; proximal organ placed close to base of segment 2 on 9–12, 10 Mm long pedicel, apical organ on 19– 27, 22 Mm long pedicel; SII slightly plumose, chaetae pectinate, chaetulae simple; S3 split in three or four branches ( Figure 6E ); pecten epipharyngis consist of three well-developed chaetae and a broad anterior scale; labral lamella with 19–24, 22 (n 53) teeth. Mentum ( Figure 6F ) with 13 teeth, median tooth with weak lateral notches, somewhat paler, all lateral teeth set in equal distance to each other; ventromental plates medially reaching third lateral tooth of mentum, MVR 1.11–1.22, 1.17; premandible ( Figure 6G ) with two teeth, well-developed brush; mandible with pecten mandibularis slightly convex ( Figure 6H ), seta subdentalis 42 Mm long; postoccipital plate ( Figure 6I ) narrow, split in middle.

Body: anterior parapods with long, simple spines; hind parapods with 16 simple hooks; L2 apparently simple; anal tubules 60–70, 63 (n 53) Mm long; supraanal seta strong, 180– 270, 240 (n 53) Mm long; procercus ca 25 Mm long with two short (ca 120 Mm long) and four long (ca 520 Mm long) anal setae, the short setae situated individually, and not on the common base of the long setae.

Remarks

A lectotype is designated to stabilize the species’ nomenclature for the future.

Stempellina ciliaris Goetghebuer, 1944 was regarded as a junior synonym of S. brevis by Brundin (1949), but examination of the type material of both species revealed that these are morphologically separable.

Stempellinella brevis is widespread in the West Palaearctic region ( Saether and Spies 2004; above), and the specimens labelled S. brevis from North America that I have seen were all misidentified specimens of S. fimbriata sp. n. described below. Thus, the record in Fauna Europaea for the Nearctic region is doubtful ( Saether and Spies 2004). The species is very similar to S. saltuum in the adult male, but can be separated by the smaller wing length to wing width ratio, lower AR, and fewer median tergite setae. Stempellinella brevis is most similar to S. flavidula in the pupal and larval stages, but can be separated from this species by smaller point patches on tergite III, continuous point patches on TVI, and the absence of shagreen on pleurae VI and VII in the pupa; longer antennal pedestal spur and longer apical Lauterborn organ pedicel in the larva.

The larvae of S. brevis build small, straight transportable cases of detritus, and have been found in brooks, streams, rivers, and lakes. Brundin (1949) found larvae of S. brevis from shore to a depth of 18 m in the oligohumic Lake Innaren and characterized the species as eurybath in subarctic lakes. Dittmar (1955) recorded the species in a stream in Sauerland, and I have found the species in both low- and high-altitude streams, brooks, and rivers in southern Norway.

Figures

Figure 5. Stempellinella brevis (Edwards), imagines. (A–F) Male: (A) head; (B) antennal flagellum; (C) wing; (D) fore, mid, and hind tibiae; (E) hypopygium; (F) superior, median, and inferior volsellae. (G, H) Female: (G) antenna; (H) genitalia.

Figure 6. Stempellinella brevis (Edwards), immatures. (A–C) Pupa: (A) frontal apotome; (B) thorax; (C) abdomen, dorsal view. (D–I) Larva: (D) antenna; (E) clypal seta S3; (F) mentum and ventromental plates; (G) premandible; (H) mandible; (I) postoccipital plate.