Riethia paluma Cranston, 2019

Cranston, Peter S., 2019, Riethia (Kieffer 1917) (Diptera: Chironomidae) revised for the Austro-Pacific region, Zootaxa 4646 (3), pp. 461-500 : 481-482

Riethia paluma Cranston sp. n.

( Fig. 4B, 4F ; 6J )

urn:lsid:zoobank.org:act:

Type material. Holotype Le/Pe/ ♀, AUSTRALIA, Queensland, Paluma, Birthday Ck., 800 m a.s.l., 18°48’S 146°09’E, 24.x.1998 (McKie) ( ANIC).

Description. Male unknown.

Female. Colour (teneral) median vitta an anterior brown oval area, with lateral vittae brown, extending from midscutum to just anterior to scutellum; scutellum pale, postnotum brown, anepisternum with broad brown ‘smudge’. Wing pale at base, infuscate from cross-veins to apex. Legs darkened at distal apices of femora and proximal base of tibia (‘knees’); tibial apices darkened near spurs; apices of successive tarsomeres brown with distalmost all dark. B.l. 6.2 mm, W.l. 2.4 mm. Head: Antenna flagellomere 137, 106, 100, 95, 165, AR 0.29; 14 clypeals, 3 clustered verticals. Palpomeres 50, 40, 205, 230, 240. Thorax. Ac?9, Dc 11, Pa 3, Scts 15. Wing V.R. 1.14. Vein setation: R with 24, R 1 with 25 and R 4+5 47–60, sq. 11. Leg lengths: P 1 1100, 1120, 1500, 600, 500, 400, 200; P 2 1200, 1160, 700, 400, 260, 200, 120; P 3 1200, 1240, 900, 540, 380, 260, 140. Ratios: LR 1 1.34, LR 2 0.44, LR 3 0.72;, BV 1 2.18, BV 2 3.12, BV 3 2.46; SV 1 1.35, SV 2 3.37, SV 3 2.62. Foretibial spur short, nearly simple 30 long; midtibial 55, 55, rear 85, 75.

Pupa. Pale yellow with darker dorsal thorax, anterior wing sheaths and lateral apophyses on posterior abdominal segments; comb brown. Cephalic area without warts, dorsal thorax rugose with multiserial rows of tubercle. Hook row on II discontinuous, occupying c. 40% of tergite width. Conjunctival spinule bands on III – IV separated from posterior tergal armament, 4–5 spinules wide, medially absent (‘divided’). Pedes spurii B absent, vortex well developed. Abdomen ( Fig. 4B ) with tergites I and II essentially bare with few very fine spinules only immediately anterior to and narrower than hookrow. TIII–VI anteriorly with transverse band of spinules, broadest on II, diminishing in lateral extent to VI, always well separated from paired posterolateral spinule patches; TVII and VIII with few finest spinules. Taeniate setae V–VIII 3, 4, 4, 5; L 3–5 on VIII clustered with respect to L 1–2. Comb ( Fig. 4F ) with 1 strong, inner spine directed postero-medially and 3–4 subordinate spines. Anal lobe with 60–65 taeniae in tightly packed biserial row.

Larva. Head capsule yellow with golden brown mental and mandibular teeth (inner only slightly darker than apical) and occipital margin narrow and dark brown. Dorsal head with clypeus ovoid-rhomboid, rounded posteriorly, clypeal setae inserted near to lateral margins ( Fig. 6J ). Antennal pedestal short. Antenna (n=1, not readily interpretable) with AR less than 1.0, segments 2-4 apparently subequal. Ventromental plate 15% longer than width of mentum. mandible with almost smooth mola, with only 1 very fine spine. Mensural features as in Table 2 .

Etymology. From the type, and so-far only known locality, Paluma, a high elevation well-studied location in the southernmost wet tropics of north Queensland. To be treated as a noun in apposition.

Diagnosis. Although the male is unknown, matching to the female should show a broadly infuscate wing, with darker band across the wing at the cross veins, and with legs darkened at the ‘knees’—the distal apex of femur and proximal apex of the tibia. Although the female holotype is quite teneral, the colour pattern will be stronger in fully hardened adults.

The pupa has a unique combination of features, although each state is shared with one or more other species yet never in combination. The hookrow on TII is medially divided (otherwise seen only in R. hamodivisa ), and the conjunctival bands, present on tergites II and IV, also are medially divided (otherwise only in R. kakadu ). The essentially bare TII is unique in the genus.

The larval head is uniformly pale, with mandibular and mental teeth golden brown. The antenna (only 1 of which is present, poorly laid out) can be determined to have a weak pedestal, a very low AR of 0.9, and ventromental plates 15% longer than the width of the mentum. The large clypeus ( Fig. 6J ), curved posteriorly with widely separated clypeal setae, is distinctive.

Remarks. Allocation of this taxon proved problematic, partially because of the lack of a male, but also because larval, pupal and female morphology do not converge on a single otherwise known species. The location, Birthday Creek near Paluma in north Queensland, is well studied, and has three other Riethia species ( R. cinctipes , R. queenslandensis and R. stictoptera ). This species cannot be allocated in any stage to these (or indeed any other) species of Riethia .

DIstribution and Ecology. Riethia paluma is known only from a single reared specimen from well-sampled creeks in the mountains of the southern wet tropics immediately north of Townsville

Figures

FIGURE 4. Riethia spp. Pupa. Abdominal tergites: A. R. noongar sp.n., B. R. paluma sp.n., C. R. plumosa Freeman, D. R. stictoptera Kieffer. Posterolateral corner of VIII (‘comb’): E. R. noongar, F. R. paluma, G. R. plumosa, H. R. stictoptera I. R. cinctipes (var), J. R. phengari sp.n., K. R. neocaledonica sp.n.. Tergites: L, IV-V of R. neocaledonica; M. Tergites VI-VIII of R. queenslandensis sp.n., N. Sternites VI-VIII R. queenslandensis, O. Tergites V-AL of R. zeylandica.

FIGURE 6. Riethia spp. Larva. Mid-dorsal head:A. R. donedwardi, sp.n., B. R. noongar sp.n.. Clypeus: C. R. larval sp. ‘C’, D. R. azeylandica sp.n., E. R. cinctipes Freeman, F. R. donedwardi sp.n., G. R. hamodivisa sp.n., H. R. neocaledonica sp.n., I. R. noongar sp.n., J. R. paluma sp.n., K. R. phengari sp.n., L. R. plumosa Freeman, M. R. queenslandensis sp.n., N. R. stictoptera Kieffer, O. R. wazeylandica sp.n., P. R. zeylandica Freeman.