Riethia plumosa Freeman
Creators: name: Cranston, Peter S.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Chironomidae
Riethia
Riethia plumosa

description: Riethia plumosa Freeman
(Figs. 1D, 2I, 4C, 4G, 6L)
urn:lsid:zoobank.org:act:
Riethia plumosa Freeman 1961.
Riethia plumosa, larva, Cranston 1966, 2000
Type material. Holotype, ♂, pinned, abdomen on celluloid mount, AUSTRALIA: Tasm [ania]. Harz Mont, 10 Dec. 1922, A. Tonnoir [ANIC]. Riethia plumosa Freeman det. Freeman 1960 (2 labels). Paratype ♂, pinned, separate hypopygium on celluloid mount, Tasm [ania], National Park [Mount Field National Park], 17 Dec.1922, A. Tonnoir [ANIC].
Other material. Collected Cranston, deposited ANIC, unless otherwise stated: New South Wales, Pe, Micalong Ck., 35°17’S 149°31’E, #2082; 2Pe, Monga SF, Mongarlowe R., 35°23’S 149°55’E, 2.iii.1991, #2080; Pe, Kosciusko N.P., Cave Ck., 35°37’S 148°39’E, 13–14.xi.1993, #2083; ♂, ♀, Spencers Ck., 36°26’S 148°20’E, 1773 m. a.sl., 3.xii.2010; 5 Pe, Murrumbidgee R., 35°38’S 148°34’E, 13–14.xi.1993, #2084; Pe, Brown Mountain, Rutherford Ck., 36°36’S 149°47’E, 16.x.1990 (Cranston & Edward), #2081.
Australian Capital Territory: 3 ♂, Brindabellas, Blundells Ck., 35°22’S 148°50’E, 13–16.iv.1988, #2079.
Victoria, P ♂, Tambo R., Teapot Creek Track, 36°57’S 147°56’E, 27.iii.1991 (Hortle), #2085.
Tasmania, 2Pe, n.e. Tasmania, nr Weldborough, R. Wild, 23–24.v.1993, #2089; 9 Pe, Cradle Mt. - L. St. Clair N.P., Dove L., 960 m a.s.l., 41°39’37”S 145°57’27”E, 25.i.2006; same except Le /P ♂, 15–30m [depth]; Le/Pe/ ♂, L. St Clair, ‘from branch @ 12 m. ’ [depth], 6.x.1972 (Martin & Timms); Pe, Frog Flat, 41°50’S 146°00’E, 25.i.1990, #2086; Pe, Backhouse Tarn, 1140 m a.s.l., 42°40’S 146°34’E, 7.ii.1992, #2090; Pe, P ♂, 2 ♂ Mount Field N.P., L. Fenton, 1006 m a.s.l., 42°40.5’S 146°37.5’E, 6.ii.1992; 2 Pe, L. Dobson, 1040 m a.s.l. 42°41’S 146°35’E, #2094; ‘tarn 1’, 42°42’S 146°48’E, 1.iii.1997 (Wright) #2312.
Description. Male. Thorax brown, without distinct vittae; legs yellow-brown to darker brown on tarsomeres, without banding. Wing membrane pale, unmarked, with yellow veins. TIX densely setose with thin setae in undivided median cluster. Genitalia (Fig. 1D) with gonostylus broad at junction with gonocoxite, bearing many apically plumose setae on inner margin. Superior volsella (Fig. 2I) with proximal basal area bearing 4–5 long setae, remainder bare except for modest posterior setose projection; medially-directed digitus tapering to point, bare of microtrichia, with 4–5 long setae; inferior volsella very small, basally appressed to inner contour of gonocoxite with short free portion linked to distal part of superior volsella, with long simple setae, without pectinate scales. No pseudovolsella. Mensural features as in Table 1.
Female. Not known with certainty.
Pupa. Pale yellow, with slightly darker dorsal thorax, anterior wing sheaths and lateral apophyses on abdominal segments V–VIII; comb yellow. Cephalothorax with almost smooth frons, weakly rugulose thorax, with bi-triserial row of tubercles running most of length of dorsal thorax beside eclosion line. Undivided hook row on II 40 –45% width of tergite; continuous conjunctival spinule band on III and IV. Pedes spurii B absent, vortex strong. Abdomen (Fig. 4C) with tergite II with triangular armament, widest posteriorly, extending to width of hookrow, tergites III–V with broad anterior spinule patch with spinules scarcely stringer than more posterior, with which they are contiguous, TVI with oval anteromedian patch separated from postero-median triangular patch. Taeniate lateral setae 3, 4, 4, 5, evenly distributed on TVIII. Comb (Fig. 4G) with 3 postero-laterally angled teeth. Anal lobe with 55–65 multiserial taeniae.
Larva. Head capsule pale yellow to golden, trace of brown on postmentum, occipital margin dark brown, mentum and inner mandibular teeth golden. Clypeus (Fig. 6L) large, trapezoidal, broadened anteriorly with clypeal setae located antero-laterally. Antenna arising from distinct pedestal, antennal ratio 1.7–1.8, with consecutive segments shorter than preceding. Inner margin of mola with one strong spine retracted from seta subdentalis position. The ventromental plate is subequal to slightly longer then the width of the mentum. Mensural features as in Table 2.
Diagnosis. The male of R. plumosa has unbanded (plain) legs, conventional shaped gonostylus with a dense cluster of plumose setae on the inner surface. The pupa is conventional with continuous hook row on TII, conjunctive V without setae, cephalic area without warts, and tergite II with only few spinules, pedes spurii B absent and TII with posterior spinule patch as wide as hook row. The larva of R. plumosa rather closely resembles that of R. phengari in the pale colour of the head capsule and extent of pigmentation of the post-occipital margin. Although R. plumosa may differ in the paler mental and inner mandibular teeth, intensity of pigmentation may vary. The clypeus of R. plumosa is diagnostically large c. 70μ wide anteriorly, and 50μ deep. The structure of the inner margin of the mandible with a single somewhat basal slender spine in plumosa, contrasts with the several broad spines on the mola of others.
Remarks. The only rearings of this species are both from north-western Tasmania, which provide the basis for the description of the immature stages. Pupal exuviae provide evidence for presence also in upland south-eastern Australia, but the apparently distinctive larvae have not been recognised elsewhere, including amongst material collected for molecular study.
Distribution and Ecology. Riethia plumosa may be the most temperate species in the genus in Australia where the species is restricted to south-eastern Australia. The most northerly record (from 35°S) is at an elevation> 900 m a.s.l. as are most records from New South Wales. Many records are from Tasmania, from where the species was described, also at elevations of c. 1000 m a.s.l.. All locations are from healthy waters, notably including from upland standing waters in national parks in Tasmania.
description: Published as part of Cranston, Peter S., 2019, Riethia (Kieffer 1917) (Diptera: Chironomidae) revised for the Austro-Pacific region, pp. 461-500 in Zootaxa 4646 (3) on pages 483-484, DOI: 10.11646/zootaxa.4646.3.3, http://zenodo.org/record/3351058