Skusella subvittata (Skuse)

Cranston, Peter S. & Tang, Hongqu, 2018, Skusella Freeman (Diptera: Chironomidae): new species, immature stages from Africa, Asia and Australia, and expanded distributions, Zootaxa 4450 (1), pp. 41-65 : 46-49

Skusella subvittata (Skuse)

( Figs 1A, C, E, F, H ; 3A–C ; 4C–D, G–H ; 5A ; 7A–B, D–G ; 8A–F )

Chironomus subvittatus Skuse, 1889: 246 ; Kieffer (1906: 22; 1917: 208).

Skusella subvittata (Skuse) ; Freeman (1961: 718); Cranston (1996: 48).

Material examined. Holotype. ♂ slide mounted in Euparal by Cranston: ‘ Walcha’ [ AUSTRALIA, New South Wales], ‘ Ch. subvittatus ♂ type’, F . A . A. Skuse , ANIC [no collection date].

Other material (collected Cranston, deposited ANIC, unless otherwise stated). AUSTRALIA: Northern Territory, 5 Pe, nr. Narbaluk, Cooper Ck, 12°18'S 133°20'E, 27.v.1988; 1 L, U. Magela Ck, Stoned Billabong, 12°38'S 132°53'E, 14.iv.1989; 1P ♂, U. Magela Ck, below Bowerbird Billabong, 12°47'S 133°03'E, 28.v.1988; 2L, Upper Magela Ck , above falls, 12°47'S 133°36E, 15.iv.1989; 1L, 2 Pe. 1 Le / Pe / ♀, Wildman R. at Arnhem Highway Crossing, 12°50'S 132°01'E, 2.vi.1988; 2 Pe, Hickey Ck, 12°55'S 132°50'S, 29.v.1988; 2 Pe, S. Alligator R. at Kakadu Highway ford, 13°17'S 132°19'E, 26.v.1988; 1 Pe, Jim Jim Ck, above falls, 13°17'S 132°51'E, 29.v.1988 (Dostine) ( ARRRI); 1 Pe, Jim Jim Gorge, 21.xi.1989 (Dostine) ( ARRRI); 1 Pe, Graveside Gorge, 13°18'S 132°32'E, 17.vii.1988 (Dostine) ( ARRRI #165 ) ; 1Pe, Koolpin Gorge, 13°30’S 132°35’E, 15–16.v.1992; 1♂, Kambolgie Ck, 13°32'S 132°23'E, 25.v.1988; 1 Pe, S. Alligator R. at Fisher Ck. , 13°33'S 132°33'E, 24.v.1988; 1 Le /P, 1Pe, Gimbat, 13°34'S 132°35'E, 24.v.1988 ; 2♂, Coronation Hill, 13°35'S 132°36'E, 4/ 5.vi.1988; 3 Pe, [ Nitmiluk N.P.] Katherine R., below gorge 1, 14°20'S 132°25'E, 21–22.v.1992 ; 1♂, Caranbirini W.H., 33 km s.w. of Borroloola, 16°19'S 136°05'E, 3.xi.1975 ( Upton , Macarthur R. survey) , 1♂, 36 km s.w. of Borroloola , 4.xi.1975; 14 km s.w. Cape Crawford, 16°47'S 135°45'E, 25.x.1975.

Queensland, 1♂, 18 km w. Mt. Carbine, McLeod R., 16°49'S 145°00'E, 7.i.1982 ( Baehr ) ( ZSM) ; 1♂, 2 km e. Einasleigh, Einasleigh R., 18°34'S 144°06'E, 11–12.vi.1993 ( Baehr ) ( ZSM); 1P/ ♂, Lawn Hill N.P., Musselbrook Ck. , upper pool, 18°37'S 138°08'E, 8.v.1995 ; 1♂, Louie Ck., Lawn Hill Crossing , 18°45.39'S 138°31.15’E, 17.v.1995, swept ; 1♂, same except light trap.

New South Wales, 1L, nr. Wooli , Lake Hiawatha, 2 m. benthic, 29°48'S 153°09’E, 1.vii.1971 (Timms); 1L, Barrington Tops, Williams River at Rocky Crossing, 32°07'S 151°29'E, 8.xii.1993 (Sydney Water); 1L, Bardon, Dusodie, ' New Park', Chichester R., 32°26'S 151°69’E, 8.xii.1993 (Sydney Water); 4 Pe, nr Araluen, Deua N.P., Deua R., 35°45'S 149°57’E, 29.iii.1989 .

Victoria, 2Pe, Little Beetle Lake, 37°47'S 148°25’E, 17.xii.1996 (Wright).

Western Australia, 1P(♂), Pilbara, Fortescue R., Fortescue Falls , 22°29.00'S 118°33.06’E, CLM 26 M (Smith); Hamersley Range N.P., Circular Pool, Fortescue Falls , 22°28'S 118°33’E, 23–24.iv.1992; 1Pe, Hamersley Gorge, 22°29.00'S 118°33.06’E, 22.iv.1992; 4 Pe , Millstream Chichester N.P., Chinderwarrinder Pool, 21°35'24"S 117°04’02"E, 25.iv.1992 ; 1Pe, Crossing Pool, 21°34'22"S 117°05’02"E, 24.iv.1992; 1 Pe , 7♂, Millstream Chichester N.P., Fortescue R., below Homestead, 21°33'S 117°03’E, 24–25.iv.1992 ; 1 Pe , Willare Bridge, Fitzroy R., 17°44'08"S 123°38'45"E, 28.iv.1992 ; 1♂, 30 km s. Warmun, Frog Hollow Ck, 17°16'S 128°03'E, 14–15.1984 (Baehr) (ZSM); Pe, Manning Gorge, 16°39'S 125°56'E, 30.v.1992; 10 Pe , Drysdale R. crossing, 15°41'S 126°47'E, 1–2.v.1992 ; 2 Pe , King Edward R., 14°53'S 126°12'E, 5–6.v.1992 ; 1♂, 14 km s.e Kalumburu, CALM site #4/3, 14°25'S 126°40'E, 3–6.1988 (Weir); 2Pe, Old Boab Camp, Crystal Ck., 14°29.42'S 125°47.26'E, 3.v.1992; 5 Pe , Mertens Falls, 13°50'S 125°43'E, 4–5.v.1992 .

Non-Australian. BRUNEI, 2 Pe, Kuala Belalong , Kuala Belalong Field Study Centre, 04°33'N 115°09'E, -. viii.1995.

NEW CALEDONIA: 2 Pe, S. Prov., Chutes de Madeleine , 22°14’S 166°52’E, 1.ii.2003; 2L, 1Pe, Mt Mou, Road Crossing, c . 200 m. asl, 22°04’S 166°20’E, 26.i.2003.

SINGAPORE: 2L, Nee Soon swamp, site #2, 01°23'N 103°48'40”E, iii.2009 (‘ NUS team’) ( TMSI).

Description. Adult male (n = 10, less for some legs). B.l. 2.9–3.9 mm, W.l. 1.4–1.8 mm.

Fl1–12 396–428. Fl13 573–682, A.R. 1.40–1.59.

Temporals 9–12 uniserial, some long; Clyp 14–26. Palp 2–5: 36–50, 136–208, 118–185, 159–318.

Thorax with double hump, anterior shallower than posterior. L.aps absent. Dc 8–14, Pa 2–3, Scts 3–9.

Wing. Plain. V.R. 1.01–1.12. Vein setation: R 11–22, R 1 9–17, R4+ 5 13–22, squamals 0–5.

Legs ( Fig. 1E ). Apically curved spur on each mid and hind outer comb, inner comb with small, blunt spur barely extending beyond longest comb teeth. LR1 2.0–2.2, LR2 0.60–0.65, LR3 0.83–0.88. BV1 1.7–1.8, BV2 3.2– 3.5, BV3 2.5–2.7. SV1 1.25–1.3, SV2 3.3–3.6, SV3 2.46–2.5.

Hypopygium ( Figs 1F, 1H ). TIX bare; anal point parallel-sided, with bluntly tapered apex. SVo ( Fig. 1H ) ca. 50–60 µm, with 2 inner setae, 15–22 long, bases 5–12 µm apart, each arising from tubercle; 3rd very fine seta, 10 long, present in some specimens either between, or distal to strong inner setae. Mvo stem ca. 30 µm, with 20–30 split semi-taeniate and simple setae. Gcx 113–160, Gst 96–108.

Adult female (n = 1) as male, except: B.l. 2.9 mm, W.l. 1.5 mm.

Antennal ratio 0.41; apical flagellomere 110. Clyp 23. Palp 2–5: 40, 190, 165, 300.

Thorax with double scutal hump, anterior shallower than posterior. L. aps absent. Dc 11–12, Pa 3; Scts 11–12.

Wing. V.R, 1.08. R 24, R1 22, R4+5 27; 1 squamal.

Legs. LR1 2.0, LR2 0.57, LR3 0.82. BV1 1.7, BV2 3.4, BV3 2.6. SV1 1 1.3, SV2 3.5, SV3 2.7.

Genitalia as in Fig. 3 .

Pupa (n = 10). Length 4.0– 4.8 mm. Exuviae pale, with only slightly darkened apophyses.

Cephalothorax. Cephalic area smooth without tubercles, pale / hyaline frontal setae 30–40 µm. Thorax with weak scutal hump at anterior 1/3 with small scales mid-thorax alongside ecdysial line. Base of thoracic horn elongate oval, tracheal bundle densely packed, 20 x 15 µm ( Fig. 4C ). Prealar tubercle rounded-triangular, darkened (Fig, 4D).

Abdomen ( Fig. 5 A ). Tergites II–VI with spinule patches laterally not reaching apophyses, and not extending to pleurae, narrower anteriorly than posteriorly; on VII and VIII spinule patches quite dense in anterior broad transverse band of spinules. Tergite II with row of 15–20 hooks extending 20–22% of tergite width. Pedes spurii B moderately developed. Pleural fringe on segments III–VIII. Posterolateral ‘comb’ on VIII with 10–14 teeth of relatively uniform size ( Fig. 4H ).

Larva (n = 2, reared). Head pale yellow with slightly darker golden-brown occipital margin, mandibles and mentum. Body length not measured. Head capsule length 450 µm, postmentum length 150 µm.

Eyespots not visible. Dorsal surface of head as in Fig. 7 A . Antenna ( Fig. 7B ) with segment lengths 87–90: 14– 15: 38–42: 24–25: 5–63; AR 1.1. Lauterborn organs alternate on segment 3, 11–12 long; blade 50–62 long, extending to apex of segment 3. Labroepipharyngeal region as in Fig. 7D , premandible ( Fig. 7E ) 75 long, with 3 apical teeth. Mandible 110–126 long, as in Fig. 7F . Mentum ( Fig. 7G ) 82–90 wide; ventromental plates 108–112 wide, separated medially by 42–45.

Abdomen. Anterior parapod claws densely clustered and very pale. Posterior parapod claws golden, squat, gently curved. Procercus 20 high by 20 wide, bearing 7–8 long pale anal setae.

Figures

FIGURE 1. Adult Skusella. A, Wing, male S. subvittata; B, Wing, female S. pallidipes (from Freeman 1958); C, Lateral thorax S. subvittata; D, Fore tibial apex; E, Hind tibial combs and spurs S. subvittata; F. Hypopygium S. subvittata (schematic, L side of figure dorsal view, R side ventral/internal); G. Hypopygium (L side dorsal) S. pallidipes; H–I Superior volsella: H, S. subvittata; I, S. pallidipes; J, Median volsella S. pallidipes.

FIGURE 3. Female Skusella, genitalia. A–C, S. subvittata (reared, Wildman R.): A, Ventral (R side of body only); B, detail including apodemes and gonapophysis VIII lobes; C, detail of labia, vagina and opening of spermathecal ducts. D–E Seminal capsule and spermathecal duct: D, S. pallidipes; E, S. freemani.

FIGURE 4. Skusella pupae. A, Cephalic area in S. sp. ‘Limuling’; B, Lateral thorax, S. sp. ‘Limuling’; C, Base of thoracic horn, S. subvittata; D, Prealar tubercle, S. subvittata; E, Sternite I, S. sp. ‘Sanyatang’; F, Part of tergite IV, S. sp. ‘Jianfengling’; G, Segments II–IV with pedes spurii B and pleural fringe, S. subvittata; H–J Segment VIII posterolateral ‘combs’, H, S. subvittata; I, S. pallidipes, J, S. sp. ‘Jianfengling’.

FIGURE 5. Skusella pupae, abdomen (dorsal). A, S. subvittata; B, presumptive S. pallidipes; C, S. freemani.

FIGURE 7. Skusella larvae. A, Head, frontoclypeus and parts farther anterior (dorsal); B–C, Antenna; D, Central labroepipharyngeal region (frontal); E, Premandible; F. Mandible; G–H, Mentum. A, B, D–G, S. subvittata; C, H, S. sp. ‘Opi’.

FIGURE 8. Skusella subvittata immature stages. A–B, Pupa: A, Segments VIII–IX; B, Segment VIII posterolateral 'comb'. C– F, Larva: C, Premandible, mandible, mentum and ventromental plates; D, Antenna; E, Mandible and part of mentum; F. Pecten epipharyngis and premandible.