Riethia phengari Cranston, 2019

Cranston, Peter S., 2019, Riethia (Kieffer 1917) (Diptera: Chironomidae) revised for the Austro-Pacific region, Zootaxa 4646 (3), pp. 461-500 : 482-483

publication ID	https://doi.org/ 10.11646/zootaxa.4646.3.3
publication LSID	lsid:zoobank.org:pub:25CA4A18-955F-4EA7-8978-E93032B54A2E
DOI	https://doi.org/10.5281/zenodo.5587168
persistent identifier	https://treatment.plazi.org/id/B3370110-9B2A-1E76-C68C-FB25FD1F3483
treatment provided by	Plazi
scientific name	Riethia phengari Cranston
status	sp. nov.

Treatment

Riethia phengari Cranston View in CoL sp.n.

( Figs. 1C View FIGURE 1 , 2H View FIGURE 2 , 4J View FIGURE 4 , 6K View FIGURE 6 )

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) GoogleMaps . 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; ♂ GoogleMaps , 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 View FIGURE 1 ). 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 View FIGURE 2 ). No pseudovolsella, inner gonocoxal setae aligned, arising from weak tubercles, more dorsal than internal on gonocoxite. Mensural features as in Table 1 View 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 View FIGURE 3 ). 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 View FIGURE 4 ), 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 View FIGURE 6 ) 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 View 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 View FIGURE 1 ) is unique. The pupa of R. phengari is near identical to that of R. azeylandica ( Fig. 3I View FIGURE 3 ) perhaps more nearly transparent without darkening and with fewer teeth in the ‘comb’ ( Fig 4J v. 4I View FIGURE 4 ). 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 View FIGURE 6 ) resembles that of R. azeylandica ( Fig. 6D View FIGURE 6 ) 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.