Stempellinella fimbriata, Ekrem, 2007

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1411-1417

Stempellinella fimbriata sp. n.

Stempellinella sp. Epler (1995) identification key to larva.

Stempellinella sp. A . Epler (2001) identification key to larva.

Stempellinella n. sp. nr. flavidula Bolton (2006) identification key to larva.

Type material

Holotype: LP „ ( USNM) USA, OH: Delaware Co., tributary to Olentangy R., N of Winter Rd, 15 October 1989, M. J. Bolton.

Paratypes: Canada: Manitoba: 2 „„ ( CNC) Southern Indian Lake, 18–20 July 1977, A. P. Wiens; 3 „„, 1 LP, 2 L, 8 Pex (VM) Churchill, Eastern Crk at road, 58.75435 ° N, 93.94933 ° W, drift 13 August 2006 and sweep net 23 August 2006, T. Ekrem; 3 „„, 4♀♀ as previous except Twin Lakes, 58.62946 ° N, 93.79774 ° W, 14 August 2006, E. Stur. Nova Scotia: 1 „ ( CNC) Cape Breton Highlands NP, 2 June 1984, M. E. Dillon. Ontario: 1 „ ( JES) Northumberland Co., N. Sevogle R., 1 August 1962, J. Marshall; 5 „„ ( CNC) Marmora, 3 June 1952, 17 May 1952, 30 May 1952, 7 May 1952, 5 July 1952, J. R. Vokeroth; 2 „„ ( JES) White Lake , 8 August 1968, 18 June 1968, R. D. Macdonald; 1 „ ( ZSM) Estaire, nr. Sudbury, 16 August 1994, G. Riedel; 5 „„ (4 JES, 1 VM), Caledon Hills, Woodrow Farm stream, 20–27 June 1980, 29 August to 5 September 1980, U. W . USA: AL: 1 „ ( JES) Auke Lake, near Juneau, 8 August 1964, G. Butaria. AR: 1 „ ( PLH) Arkansas Co., White R., White R. Natl. Wildlife Ref., SR1 bridge nr. St. Charles boat ramp, 22 June 2001, Chordas and Chapman. FL: 1 P(„) ( JHE) Hamilton Co., Hunter Ck., 21 March 2000, J. H. Epler; 1 LP („) ( JHE) Hamilton Co. , Camp Branch , 1 May 2001, J. H. Epler; 1 LP („) ( JHE) Wakulla Co. , Tiger Hammock , 14 April 1991, J. H. Epler; 1 LP, 1 LP (♀), 1 P(„) ( JHE) Jackson Co., Chipola River, Stump Creek at state highway 231, south of Alford, 12 June 1984, 17 July 1984, leg. W. R. Karsteter; 1 P „, 1 LP „ ( JES), Clay Co., Black Ck., drainage, W. Beck. GA: 1 „ ( JES) Ware Co. , Satilla River , Hwy 1-23, 5 April 1978. MI: 1 L ( PLH) Mackinac Co. , Sta. 12C, 1997, D. Schoellser; 2 L ( PLH) Chippewa Co. , St Mary’s R., Neebish Island , 8 June 1995, M. Blouin. MN: 3 Pex ( UMSP) Anoka Co. , Cedar Ck., upstream CR24, 45.4031 ° N, 93.2094 ° W, 5 May 2004, R. W. Brouchard Jr.; 1 Pex ( UMSP) Chisago Co. , Rock Ck., 45.7143 ° N, 92.8749 ° W, 6 June 2003, L. C. Ferrington Jr.; 1 Pex ( UMSP) as previous except Sunrise River , 3 October 2003. NC: 1 „ ( JHE) Haywood Co., GRSM, Palmer Ck., at light, 841 m a.s.l., 13 September 1995, G. Salinsky and H. Soehn. NH: 2 „„ ( JES) Mt. Washington, small creek, 3000 ft, 12 August 1961, W. W. Wirth. NM: 1 „ ( JES) Sandoval Co., Rio Guadalupe, above tunnels, 16 July 1992, R. Castell; 1 Pex ( JES) Sandoval Co., San Antonio R. above La Cueva campgrounds, 17 August 1994, Jacobi/Zamora; 1 Pex ( JES) Sandoval Co., E. Fork, Jemenez River below Las Conchas campground, 8 July 1993, P. Martinez; 1 Pex ( JES) Sandoval Co., San Antonio R., 14 July 1992, R. Castell; 1 „ ( JES) San Miguel Co., Sapello R., 8 June 1970, light trap, G. Harrell; 2 Pex ( JES) San Miguel Co. , Pecos River , 200 m below Lisboa Hat. , 21 July 1992, R. Castell; 4 Pex (3 JES, 1 VM) Grant Co. , Mimbres River , Cooney campground, 29 July 1992, R. Castell; 3 Pex (2 JES, 1 VM) Catron Co. , Gilita Ck., above Willow Ck., 29 July 1992, 3 September 1991, R. Castell; 1 Pex as previous except Willow Ck., 3 September 1991; 1 Pex ( JES) Catron Co. , Whitewater Ck. below Catwalk, 16 August 1991, M. Hatch; 1 Pex ( JES) Catron Co. , Trout Ck., 22 July 1992, D. James; 1 Pex ( JES) Catron Co. , below Beaver Dam, 2 October 1992, M. Doles. NY: 2 P(„„), 2 „„ ( KWS) Lewis Co. , Lyonsdale, Moose R, 7 September 1978, K. W. Simpson; 1 P(„) ( KWS) Greene Co., Tannersville, Schoharie Ck., 26 August 1975, K. W. Simpson OH: 1 „ ( MJB) Preble Co. , Twin Ck., Halderman Rd, 15 September 1986, M. J. Bolton; 1 „ ( MJB) Franklin/Mad. Co., Big Darby Ck., Amity Rd, 17 April 1991, M. J. Bolton; 1 LP ( MJB) Preble Co., Sevenmile Ck., Eaton, N. Hope Rd, 16 September 1991, M. J. Bolton; 4 L ( MJB) Washington Co., L Muskingum R, adj. SR26, dst. Sacket Run, 23 August 2000, C. E. McKnight; 3 LP (VM) Champaign Co., Little Darby Ck., at Route 29, 5 September 1992, M. J. Bolton; 1 „ ( JES) Batavia, Little Miami R, Sportsman Park, 16 January 1969, W. T. Mason; 8 „„ ( PLH) Clermont Co. , East Fork , Little Miami R, Proctor & Gamble Experimental Channels, 15 September 1999, 5 September 1997, 25 June 1997, 12 September 1996, 23 September 1998, 2 July 1998, 14 September 1997, 28 June 2000, P. L. Hudson. SC: 7 „„ (6 JES, 1 VM) Aiken Co. , Upper three-runs Ck., Savannah R Plant, 11 February 1977, 26 February 1977 H. Prickard, 16– 17 November 1979, 27 November 1979, 12–13 October 1979, 16 February 1979, 24–25 April 1980, P. L. Hudson; 1 „ ( JES) as previous except Tinker Ck., 26 February 1977, H. Pickard; 1 „ ( JES) Oconee Co. , Yellow Branch Ck., 29 September 1974, P. L. Hudson; 2 „„ ( JES) Williamsburg Co. , Kingstree, Black River , 26 April 1980, P. L. Hudson; 1 P(„) ( JES) Pickens Co., Wildcat Ck., May 1978. VA: 1 „ ( JES) Rockbridge Co. , Vesuvius, light trap, July 1960, D. H. Messersmith. WI: 2 „„, 2 Pex ( ZSM) Madison, Trout Lake , September 1962, E. J. Fittkau; 6 L ( PLH) Bayfield Co. , Lake Superior , off Stockton Island , 18 June 1973, 27 June 1972, 21 August 1973, 5 November 1973; 1 P(„) ( PLH) Bayfield Co. , Lake Superior , Apostle Isl. Region , Gull Island Skaal, Lake trout stomach # 207 .

Etymology

‘‘Fimbriata’’, Latin adjective meaning fringed, referring to the fringed appearance of the median volsellae.

Diagnostic characters

Stempellinella fimbriata can be separated from other Stempellinella species by the following combination of characters: adult male with AR 0.7–1.0; anal point with 9–15 strong spinulae between well-developed anal crests; strong median setae on anal tergite; lateral anal tergite setae absent; setiger of superior volsella narrow basally, width shorter than horizontal distance between superior and median volsellae; median volsella 40–50 Mm long with microtrichose, palmate stem. Adult female with AR 0.38–0.44; vaginal floor large, covering almost half of vagina ventrally; spermathecal ducts longer than notum and rami combined; notum longer than rami; diameter of seminal capsules lower than length of notum; coxosternapodeme with anterolateral lobe; gonocoxite IX without setae; sternite VIII with more than 35 setae. Pupa with conical cephalic tubercles and moderately wrinkled frontal apotome; thorax completely brown pigmented and extensively granulated, median antepronotal on weak tubercle; one lateral seta on abdominal segment III and IV taeniate, anterolateral patches of shagreen on tergites VII–IX. Larva with 50–75 Mm long, digitiform, curved spur subapically placed on antennal pedestal, AR 0.8–1.0; premandible with four teeth; S3 split in three branches.

Description

Adult male (n 5 5, unless otherwise stated). Total length 1.3–1.9, 1.6 mm; wing length 0.87– 1.28, 1.16 (n 57) mm.

Colour: head and thorax brown with somewhat darker scutal stripes, eyes dark brown, abdomen and legs pale yellow-brown.

Head ( Figure 15A, B ): eyes without dorsomedian elongation; frontal tubercle large, conical, 10–12, 11 Mm long; antenna with 13 flagellomeres of which only 10 are easily discernible ( Figure 15B ); AR (on 10 flagellomeres) 0.71–1.04, 0.89; lengths of palpomeres (in Mm): 20–25, 21; 20–35, 25; 65–80, 73; 80–95, 87; 115–140, 124. Clypeus about 40 Mm long with 8–13, 9 setae; tentorium ca 90 Mm long, 15 Mm wide; three or four inner verticals, two or three outer verticals, two to four postorbitals.

Thorax: scutal tubercle absent; acrostichals 9–12, 10; dorsocentrals 5–7, 6; humerals 0; prealars 1; scutellars 5–7; halterals 3–5.

Wing ( Figure 15C ): cuneiform, 3.1–3.5, 3.3 times longer than broad; VR 1.52–1.56, 1.54; wing setation as in Figure 15C .

Legs ( Figure 15D ): 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 ( Figure 15E, F ): anal tergite 88–102, 97 Mm long with transverse anal tergite band, three to six, four strong median setae far from anal point base, frequently one to three small setae near base; lateral anal tergite seta absent; anal point 40–47, 44 Mm long, basally 9–13, 11 Mm broad with well-developed crests, distally thin and pointed; 9–15, 12 strong spinulae between anal crests; microtrichia present around base of anal point. Gonocoxite 67–93, 79 Mm long; gonostylus 40–52, 47 Mm long; HR 1.60–1.78, 1.69. Superior volsella ( Figure 15F ) comparatively large, setiger more or less drop-shaped, medially directed, base narrower than horizontal distance between superior and median volsellae, four or five dorsal setae, two median setae, basomedian seta on small ventral tubercle, superior volsella otherwise bare, apex medially directed; digitus absent but angled contour present ventrally on setiger; median volsella 38–50, 43 Mm long, posteromedially directed, palmate stem with long microtrichia, with simple 10 Mm long lamellae; inferior volsella 50–70, 61 Mm long, slightly club-shaped, with five or six distal setae, dorsal surface without microtrichia.

Adult female (n 5 4, unless otherwise stated). Total length 1.1.5–1.9, 1.7 mm; wing length 1.04–1.13, 1.10 mm.

Colour: yellow-green ground colour; head pale brown with dark brown eyes and apeces of antennae; thorax with brown scutal stripes, postnotum, median anepisternum, pale brown preepisternum, antepronotum and epimeron II, scutellum pale with darker margins; abdomen pale yellow.

Head: as male, except cephalic tubercles weak mounds, 5 Mm long; antenna ( Figure 15G ) with five flagellomeres, ultimate flagellomere 70–75, 73 Mm long, AR 0.38–0.44, 0.41; lengths of palpomeres (in Mm): 15–20, 16; 22–25, 24; 50–65, 60; 75–80, 86; 100–115, 105 (n 53). Clypeus with 9–12 setae.

Thorax: acrostichals 11–15, 13; dorsocentrals 8; humerals 2–3; prealars 1; scutellars 5–8, 7; halterals 4–6, 5.

Wing: as male, except 2.7–2.9, 2.8 times longer than broad. VR 1.51–1.61, 1.55.

Legs: as male.

Genitalia ( Figure 15H ): tergite IX semicircular, 63–75, 71 Mm long; sternite VIII with 37–46, 42 setae, of which none to two are placed on vaginal floor; vaginal floor large, covering almost half of vaginal opening ventrally; gonapophysis VIII single lobe with long posteromedially directed microtrichia; gonocoxapodeme slightly curved; coxosternapodeme well developed with broad anterior and posterior lobes. Notum including rami 120– 130, 124 Mm long, notum alone ca 90 Mm long. Seminal capsules ovoid, diameter 50–60, 56 Mm with ca 170 Mm long spermathecal ducts. Postgenital plate triangular. Cercus 45–50, 49 Mm long.

Pupa (n 5 5, unless otherwise stated). Total length 1.8–2.6, 2.2 mm; abdomen 1.4–1.8, 1.6 mm long. Colour of pupal exuviae: thorax completely brown, abdomen clear with darker lateral margins on segments VII–IX, tergites VII and VIII with dark pigmentation posteriorly.

Cephalothorax ( Figure 16A, B ): cephalic tubercle well developed, conical, 25–40, 35 Mm long; frontal setae taeniate, 160–225, 188 Mm long; pedicel sheath tubercle absent. Thoracic horn 275–372, 322 Mm long with some 5 Mm long chaetae distributed dorsally on distal half, most in middle; precorneals taeniate, arranged in slight triangular pattern, the two anteriormost setae situated closer to each other than to the third, anterior and posterior precorneals ca 230 Mm long, longer than median precorneal (165–175, 171 Mm long); one taeniate median antepronotal ca 240 Mm long on low tubercle, two lateral antepronotals (one sensillum basiconicum); two pairs of fine dorsocentrals, setae of each pair equally strong, 25–40, 35 Mm long. Extensive fields of granulation and fine sculpturing present on thorax, a few stronger granules present along median suture line. Prealar tubercle well developed, wide; nose of wing sheath strong.

Abdomen ( Figure 16C ): TII with developed subtriangular point patches; hook row 55– 100, 72 Mm wide with 24–33, 28 hooks. TIII–VI with more or less p -shaped point patches, patches on TIII somewhat smaller; TVII–IX with small anterolateral patches of shagreen. Segment II with well-developed pedes spurii B; segment IV with pedes spurii A. Segment II with 2 D, 2 V, 3 L setae; segment III with 3 D, 3 V, 2 L, 1 taeniate or semi-taeniate L setae; segment IV with 3 D, 3 V, 2 L, 1 taeniate L setae; segment V with 3 D, 4 V, 3 taeniate L setae; segment VI–VII with 3 D, 4 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, 16–25, 19 (n 56) taeniate setae in anal fringe. One pair of O-setae present anteriorly on tergites II–VIII. Pleurae III–VII with shagreen. Posterolateral spur on segment VIII well developed.

Larva (n 5 5, unless otherwise stated). Total length ca 1.9 mm, house ca 2.3 mm. Head capsule yellow, brown postoccipital rim and teeth on mandible and mentum. Live individuals not examined.

Head ( Figure 16D–I ): AR 0.81–0.97, 0.89 (n 56); antennal pedestal 68–80, 74 Mm long with strong, subapical, 50–70, 63 (n 56) Mm long digitiform spur; antenna ( Figure 16D ) with all segments well sclerotized, segment lengths (in Mm, n 56): 55–70, 63; 38–43, 39; 12–15, 13; 10– 13, 12; 6–7; segment 3 inserted subapically on segment 2; AAR 1.07–1.29, 1.19. Antennal seta placed at base just above ring organ; antennal blade 80–100, 87 Mm long, pale, reaching well beyond tip of antenna; peg of antennal segment 2 placed at two-thirds length of segment. Lauterborn organs large, bulbous, 18–23, 20 Mm long; proximal organ placed at one-quarter length of segment 2 on 5–10 Mm long pedicel, apical organ on 15–25, 20 Mm long pedicel; SII and chaetae plumose; chaetulae simple; S3 long and split in three branches ( Figure 16E ); pecten epipharyngis consist of three well-developed chaetae; labral lamella with 20–22 (n 53) teeth. Mentum ( Figure 16F ) with 13 teeth, median tooth with low lateral notches, all teeth equally dark; ventromental plates medially reaching third lateral tooth of mentum, MVR ca 1.1–1.2; premandible ( Figure 16G ) with four teeth, sometimes only three visible, with welldeveloped brush; mandible ( Figure 16H ) with pecten mandibularis slightly convex, seta subdentalis 35–43, 39 Mm long, reaching well beyond apex of mandible, mola with two basal spines; postoccipital plate ( Figure 16I ) well developed, split.

Body: anterior parapods with long, simple spines; hind parapods with 14–18 simple hooks; L2 apparently simple; anal segment without or with very short anal tubules; supraanal seta strong, 200–275, 245 (n 53) Mm long; procercus with two short (ca 130 Mm long) and four long (ca 525 Mm long) anal setae, the short setae situated individually, and not on the common base of the long setae.

Remarks

Stempellinella fimbriata is very similar to S. tamaseptima in the adult male, but can be separated by the differently shaped superior volsella, and the longer distance between superior and median volsellae (longer than width of setiger base in S. fimbriata ). The pupae of S. fimbriata show some variation in the extension of the point patches on the abdominal tergites II–VI which can be more extensive than seen in Figure 16C .

The species has been recorded from many streams and small rivers throughout North America (see above) and also from the sublittoral and profundal zones in Canadian lakes (G. A. Halvorsen, personal communication). The larvae build transportable cases of comparatively coarse sand and detritus.

Figures

Figure 15. Stempellinella fimbriata sp. n., imagines. (A–F) Male: (A) Head; (B) antenna; (C) wing; (D) fore, mid, and hind tibiae; (E) hypopygium; (F) superior, median, and inferior volsellae. (G, H) Female: (G) antenna; (H) genitalia.

Figure 16. Stempellinella fimbriata sp. n., 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.