Stempellinella tamaseptima (Sasa)

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1443-1447

Stempellinella tamaseptima (Sasa)

Tanytarsus tamaseptimus Sasa 1980, p 22 . 3 „„ syntypes with associated Pex, Japan, Tokyo, Minamiasakawa River , station 1, 17 August 1979, Sasa et al. [not examined].

Stempellinella tamaseptima ( Sasa, 1980) . Kobayashi (1990) new combination, Sasa (1990) distributional data.

Material examined

Canada: British Columbia: 1 „ ( ZSM) Clinton, Loon Creek Fish Hatchery, 1–2 June 1976, I. M. Smith; 1 „ ( ZSM) Caycuse , 17–18 June 1979, I. M. Smith . Japan: 3 „„ ( NSMT) Toyama, Kumano River, Monjuji-hashi , station 5, 30 May 1989 (No. 207: 45–47); 2 „„ (VM) Hiroshima, Ichikawa, Shiraki , 21 October 2003, E. Inoue; 1 „ (VM) Hiroshima, Shobara, Hiwa , 24 December 2003, E. Inoue; 2 „„, 5♀♀ (VM) Kanagawa Pref., Kawasaki, Ikuta Green Park , 35 ° 369370N, 139 ° 339250E, emergence, 8 February 1992, T . Kobayashi .

Diagnostic characters

Stempellinella tamaseptima can be separated from other Stempellinella species by the following combination of characters: adult male with AR 0.6–1.0; anal point with numerous strong spinulae between well-developed anal crests; strong median setae on anal tergite; lateral anal tergite setae absent; setiger of superior volsella roughly rectangular with concave median margin, base wider than horizontal distance between superior and median volsellae; median volsella 35–40 Mm long with microtrichose, palmate stem. Adult female with AR 0.31–0.35; few or no setae on vaginal floor; seminal capsules 54–60 Mm in diameter; spermathecal ducts longer than notum and rami combined, and usually longer than 200 Mm; notum longer than rami; coxosternapodeme with obvious anterolateral lobe. Pupa with separate point patches on abdominal tergites III – VI; one lateral seta on abdominal segment III and IV taeniate, large anteromedian patch of shagreen on tergite VII; anterolateral patches of shagreen on tergites VIII –IX.

Redescription

Adult male (n 5 5, unless otherwise stated). Total length 1.1–1.8, 1.4 mm; wing length 0.80– 1.20, 1.02 (n 57) mm.

Colour: head and thorax pale brown with dark brown pedicels, eyes, scutal stripes, postnotum, median anepisternum II, and ventral part of epimeron II, pedicels darker dorsally, eyes darker ventrally; abdomen yellow-green.

Head ( Sasa 1980, Plate 20, Figures A–C): eyes without dorsomedian elongation; frontal tubercle large, conical, 9–15, 12 Mm long; antenna ( Figure 28A ) with 13 flagellomeres of which only 10 are easily discernible; AR (on 10 flagellomeres) 0.56–0.96, 0.78, Sasa (1980) reports 0.68–069; lengths of palpomeres (in Mm): 20–25, 21; 20–30, 24; 60–75, 68; 75–90, 84; 125–130 (n 52). Clypeus about 45 Mm long with 10–12, 11 setae; tentorium ca 90 Mm long, 15 Mm wide; two or three inner verticals, two or three outer verticals, two to four postorbitals.

Thorax ( Sasa 1980, Plate 20, Figure I): scutal tubercle absent; acrostichals 9–12, 11; dorsocentrals 5–6; humerals 0–2; prealars 1; scutellars 4–6; halterals 5–6.

Wing ( Figure 28B ): cuneiform, 2.9–3.3, 3.1 times longer than broad; VR 1.50–1.64, 1.58 (6); wing setation as in Figure 28B .

Legs ( Sasa 1980, Plate 20, Figures E–H): fore tibia with 15 Mm long spur; mid and hind tibiae with well separated, 10–12 Mm long tibial combs, one comb on each tibia with 24–35, 27 Mm long spur; tarsi without sensilla chaetica; pulvilli absent. Lengths and ratios of leg segments in Table III.

Hypopygium ( Figure 28C–E ): anal tergite 75–100, 88 Mm long with transverse anal tergite band, three to six, four strong median setae far from anal point base, sometimes one to three smaller setae near base; lateral anal tergite seta absent; anal point 36–45, 40 Mm long, basally 6–10, 9 Mm broad with well-developed crests, distally usually thin and pointed ( Figure 28D ); 9–16, 12 (n 57) strong spinulae between anal crests; microtrichia present around base of anal point. Gonocoxite 70–80, 75 Mm long; gonostylus 42–55, 47 (n 57) Mm long; HR 1.45–1.86, 1.60. Superior volsella ( Figure 28E ) comparatively large, setiger with rectangular appearance, concave median margin, five dorsal and two median setae on medially directed apex, superior volsella otherwise bare, base of setiger broader than horizontal distance between superior and median volsellae; digitus absent; median volsella 35–40, 39 (n 57) Mm long, posteriorly directed, palmate stem with long microtrichia, with simple 10 Mm long lamellae; inferior volsella 45–65, 55 (n 57) Mm long, slightly club-shaped, with five or six distal setae, dorsal surface without microtrichia.

Adult female tentatively associated (n 5 5, unless otherwise stated). Total length 1.3–1.5, 1.4 (n 53); wing length 1.08–1.13, 1.10.

Colour: as male except antennal pedicels pale.

Head: as male, except cephalic tubercles 8–9 Mm long; antenna ( Figure 28F ) with five flagellomeres, ultimate flagellomere 60–67, 64 Mm long, AR 0.31–0.35, 0.33; lengths of palpomeres (in Mm): 18–24, 22; 24–30, 26; 60–75, 65; 69–87, 78; 120 (n 54). Clypeus with 9–15, 11 setae.

Thorax: scutal tubercle weak hump; acrostichals 14–17, 15; dorsocentrals 5–8, 6; humerals 3–4; prealars 1; scutellars 6–9, 7; halterals 5.

Wing: as male, except 2.8–3.0, 2.9 times longer than wide; VR 1.48–1.74, 1.60.

Legs: as male.

Genitalia ( Figure 28G ): tergite IX semicircular, about 45 Mm long; sternite VIII with 19–38, 27 setae, of which none to two are placed on vaginal floor; gonapophysis VIII single lobe with long posteromedially directed microtrichia; gonocoxite IX with one or two setae; gonocoxapodeme slightly curved; coxosternapodeme well developed with obvious anterior and posterior lobes. Notum including rami 111–126, 118 Mm long, notum alone ca 63–70 Mm long. Seminal capsules ovoid, diameter 54–60, 55 Mm with 195–225, 209 Mm long spermathecal ducts. Postgenital plate subtriangular. Cercus 40– 50, 45 Mm long.

Pupa (from Sasa 1980, p 22, Plate 22). Length of abdomen 1.37–1.45 mm. Colour of pupal exuviae unknown, but at least abdominal segments VIII –IX are darkened laterally.

Cephalothorax: thoracic horn 470–490 Mm long with few chaetae on distal half.

Abdomen: TII with central, rectangular point patch; hook row with ca 30 hooks. TIII – VI with paired central point patches, patches on TIII considerably smaller; TVII with anteromedian, rectangular patch of shagreen; TVIII –IX with small anterolateral patches of shagreen. Pedes spurii A and B not apparent in drawing. Segment II with 4 D, 3 L setae; segment III with 4 D, 2 L, 1 taeniate L setae; segment IV with no dorsal setae in original drawing, 2 L, 1 taeniate L setae; segment V with 4 D, 3 taeniate L setae; segment VI – VII with 4 D, 4 taeniate L setae, segment VIII with 1 D, 3 taeniate L setae; segment IX without dorsal seta on anal lobe, 16 taeniate setae in anal fringe. Posterolateral spur on segment VIII well developed.

Remarks

The slide box containing the type material (A43) appears to be missing from the Sasa collection at NSMT ( T. Kobayashi, personal communication) and the type material was therefore unavailable for examination. The females described here are tentatively associated with the males. Both sexes were found at the locality in Kawasaki and the females are morphologically different from the other Stempellinella species recorded in Japan. Unfortunately no pupae were available for this study, and the original pupal description differs considerably from the typical Stempellinella pattern. For instance, no Stempellinella species has so far been seen with the abdominal tergal armament and setation described for S. tamaseptima ( Sasa 1980, Plate 22), a pattern found to be relatively constant in both Stempellinella and Zavrelia . Thus, there is a chance that Sasa’s description of the pupa is inaccurate, and that most of the deviations from closely related Stempellinella species (e.g. S. fimbriata and S. truncata ) are due to misinterpretations by Sasa. The material used by Sasa (1990) is in bad condition. Two of the specimens are unrecognizable, and one specimen (No. 207: 45) is a Tanytarsus .

Stempellinella tamaseptima is known from unpolluted upper reaches of river systems in Gifu, Hiroshima, Kanagawa, Nagasaski, Okinawa, and Tokyo prefectures in Japan ( Sasa 1980; T. Kobayashi, personal communication), from the Russian Far East ( Makarchenko et al. 2005), and from British Columbia in Canada. Although unknown, the larvae probably build straight cases of fine sand and detritus, and are likely to be found in areas of streams and rivers where this substance is available.

Figures

Figure 28. Stempellinella tamaseptima (Sasa), imagines. (A–E) Male: (A) antennal flagellum; (B) wing; (C) hypopygium; (D) variation in anal point; (E) superior and median volsellae. (F, G) Female: (F) antenna; (G) genitalia.