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

description: Riethia phengari Cranston sp.n.
(Figs. 1C, 2H, 4J, 6K)
urn:lsid:zoobank.org:act:
Riethia “moonlight” Cranston, 1966, 2000
Type material. Holotype Le /P ♂, Australian Capital Territory (ACT), Moonlight Hollow, 35°25’S 148°47.30’E, 20.x.1991 (Cranston) (ANIC). Paratypes (all collected Cranston, deposited ANIC): Le / Pe, as holotype; 2L, Brindabellas, Blundell's Ck., 35°22'S 148°50'E, 24–27.viii.1988; ♂, Blundell's Ck., no further data (Colless); Pe, Condor Ck., 35°22’S 148°51’E, 27.x.1991.
Other material. Unreared larva, excluded from paratype series. Tasmania, South George R., intake bridge, undated, 41°18.39”S 147°56.02”E (MV, failed, TAS3).
Description. Male. Thorax yellow-brown without distinct vittae; legs yellow-with slightly darker tarsomeres, without banding. Wing pale, unmarked, with yellow veins. TIX with fine setae dense across complete tergite. Gonostylus broad at junction with gonocoxite, abruptly attenuated, bearing dense brush of broad, apically plumose setae on inner margin (Fig. 1C). Superior volsella with basal area bearing proximally 4 long setae, remainder bare except for posterior setose projection; medially-directed digitus virtually devoid of microtrichia, with 3 long setae; inferior volsella very small, almost totally appressed to inner contour of gonocoxite and linked to posterior part of superior volsella, with long simple setae; junction between superior volsella and inferior volsella bears 1 pectinate scale (Fig. 2H). No pseudovolsella, inner gonocoxal setae aligned, arising from weak tubercles, more dorsal than internal on gonocoxite. Mensural features as in Table 1.
Female unknown.
Pupa. Very pale, almost translucent, with pale yellow dorsal thorax, anterior wing sheaths and lateral apophyses on abdominal segments V–VIII; comb pale yellow. Cephalothorax with almost smooth frons, thorax weakly rugulose with bi-triserial row of small tubercles along dorsal thorax each side of eclosion line. Hook row continuous on II, 45–50 % width of tergite; conjunctival spinule band on III and IV continuous. Pedes spurii B absent, vortex weak. Abdomen with tergite II with armament full width of hookrow posteriorly, tapering anteriorly and then expanded to form quite strong anterior transverse band of stronger spines; TIII–V similar to R. azeylandica (Fig. 3D). TVIII and anal lobe bare. Taeniate setae V–VIII 3, 4, 4, 5, on VIII evenly distributed along segment. Comb with 1 strong postero-laterally directed tooth (Fig. 4J), with or without 1–2 very small lateral teeth. Anal lobe with c 55–60 bidisorganised multiserial taeniae.
Larva. Head capsule golden, slightly browner on postmentum, occipital margin broad, dark brown, mentum and four inner mandibular teeth similarly golden-brown. Clypeus (Fig. 6K) trapezoid, stippled at least in posterior half. Inner margin of mandible with 2–3 strong serrations on mola commencing close to insertion of seta subdentalis. Each antennal segment shorter than preceding. The ventromental plates are 10–20% wider than the mentum. Mensural features as in Table 2.
Etymology. From φεγγάρι (phengári) Greek for moonlight, after the type locality of Moonlight Hollow.
Diagnosis. In the male the attenuated gonostylus (Fig. 1C) is unique. The pupa of R. phengari is near identical to that of R. azeylandica (Fig. 3I) perhaps more nearly transparent without darkening and with fewer teeth in the ‘comb’ (Fig 4J v. 4I). The larva of R. phengari has a pale mentum and inner mandibular teeth scarcely darker than the uniformly pale-golden head. The antennal pedestal is very short and the AR is between 1.6 and 1.8 with the 3 rd segment shorter than 2 nd. The clypeus (Fig. 6K) resembles that of R. azeylandica (Fig. 6D) but may be more rectangular and can have stippling in the posterior half.
Remarks. Based on the immature stages alone, R. phengari would be poorly differentiated from R. azeylandica. The attenuated gonostylus of the reared holotype is seen also in a prior-collected male from close-by, housed in the ANIC. The genitalia are totally symmetrical so evidently this gonostylus is not teratological but represents a distinctive new species. The species is unrepresented by molecular material.
DIstribution and Ecology. Riethia phengari is limited to a very small area of eastern Australia coincident with the mountains of the Australian Capital Territory. The streams are 2nd or 3rd order, in a region very widely surveyed including by drift netting over extended periods.
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 482-483, DOI: 10.11646/zootaxa.4646.3.3, http://zenodo.org/record/3351058