Yarrhpelopia, Cranston, Peter S., 2017

Cranston, Peter S., 2017, A new genus and species of Australian Tanypodinae (Diptera: Chironomidae) tolerant to mine waste, Zootaxa 4263 (2), pp. 369-377 : 370-371

Yarrhpelopia gen. nov.

( Figs. 1–3 )

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Pentaneurini genus A ( Cranston 1996, Krosch et al. 2007)

Diagnosis. Adult male. Pedicel setose, flagellomeres with dark plumes; terminal segment of male short, darkened, with apical fine seta ( Fig. 1 A). Wing ( Fig. 1 B) translucent, veins including crossveins pale, membrane and all veins densely setose; costa (C) extending to apex of R4+5 prior to wing apex, and proximal to end of M3+4; R1 and R4+5 narrowly separated such that R2+3 is poorly visible, but a faint R2 seems to connect to apex of R1 and costa; R4+5 runs close to and terminates in costa. Squama setose, uniserial. Tibial spurs ( Fig. 1 C) 1, 2, 2: elongate with several side teeth, inner spur on t2 and t3 50–60% length of outer, tibial comb of 3 spines on apex of hind tibia; pulvilli absent; claws very slender, pointed. Posterior margin of TIX with 5–6 long setae. Hypopygium ( Fig. 1 D) with mediobasal spinose lobe, possibly representing volsella. Parameres strong, long, and dark within cleared gonocoxite ( Fig. 1 D left).

Pupa. With elongate flat-tubular thoracic horn, about 3–4× as long as broad with horn sac near filling lumen, contracted strongly in distal 1/4 with narrow neck connecting to laterally orientated ovoid plastron plate, filling half of surrounding corona; corona oval, faintly defined, occupying c. 25% of length of horn. Thoracic horn (except corona) with complete dense cover of pointed scales. Thoracic comb modestly developed, uniserial row of 5–7 short, apically rounded tubercles. Basal lobe dome-shaped. Thorax smooth. Tergite I with pigmented scar. Shagreen of small tubercle /spinules, dense and aligned in rows of 2–4; L(ateral) setae taeniate on VII (4) and VIII (5), anal lobe outer margin with very fine spines, inner bare, anal setae adhesive.

Larva. Head index c. 0.5; ligula 5-toothed with weakly concave tooth row, inner teeth weakly curved outward and mid-tooth slightly recessed; 2nd antennal segment smooth, AR c. 3, ring organ at c. 60% from base. Lauterborn organs short and apex does not resemble 'tuning fork'. Basal palp segment undivided, ring organ at 75% from base; b sensillum of two sections, basal section about 3 times length of apical section. Mandible with seta subdentalis arising on strong distal molar 'tooth', posterior to well-defined, rounded inner tooth. SSm retracted, V9, VP and V10 near aligned 45° to longitudinal axis, with ventral pit (VP) slightly posterior to V9–V10; dorsal pit (DP) present, S7 separated from S8. Body without swim hairs. Parapod claws simple, pale.

Type species. Yarrhpelopia norrisi sp.n.

Etymology. Yarrh (pronounced with silent ‘h) derives from the southern New South Wales Aboriginal Ngunnawal language meaning 'running water', recognising the ecology of the genus and its centre of distribution, and— pelopia, a common suffix in Tanypodinae , the suppressed Pelopia.

Distribution. Australian endemic, probably monotypic, distributed along the eastern margin of Australia, from 30°S to 42°S. Apparently absent from northern and western Australia.

Remarks. All stages of Yarrhpelopia conform to diagnoses of the tribe Pentaneurini , but each differs in generic identity according to respective stage keyed. In the key to larval Tanypodinae of the Holarctic region ( Cranston & Epler, 2013) the simple palpal base, slightly recessed central ligula tooth, body lacking fringe, antennal peg sensilla absent, strong molar tooth, conventionally short posterior parapods, and smooth head and antennal length 3.5× mandible and medially located ring organ leads to couplet 33. The presence of a dorsal pit and simple small posterior parapod claws conform to Larsia whereas the ligula shape and A.R. of less than 3.5 suggest Zavrelimyia . In Cranston (1996), the larva is keyed as 'genus A' as distinct from other Australian genera on the basis of the distribution of cephalic setae and pits, and on the sculpturing ('creasing') of the postmentum and gula. However Cranston's (loc. cit.) interpretation of the inner teeth of the ligula as directed anteriorly is erroneous as unworn teeth have an outwardly directed apex.

Regarding the pupa, in the key of Fittkau & Murray (1986) the unfringed, narrow anal lobe indicates Pentaneurini , within which the dense simple spines of the abdominal shagreen preclude the Thienemannimyia group of genera. The presence of 4 LS on segment VII and adhesive sheaths on anal macrosetae, distinct thoracic comb, corona on thoracic horn and male genital sacs extending to 70% of length of the anal lobe that lacks spines on the inner margin leads to couplet 39. Yarrhpelopia has both transverse serial spinule (shagreen) groups of Larsia and simple spinules of Zavrelimyia (Zavrelimyia) : the thoracic horn lacks the characteristically lobate respiratory atrium of Larsia . Keyed as 'genus A' ( Cranston, 1996) it is close to Paramerina (now Zavrelimyia ) based largely on the thoracic horn (tubular, non-lobate atrium, corona present, plastron plate apical with coarse surface), but differs from Zavrelimyia (Paramerina) in the horn being spinose distally as far as the corona.

In the adult male if the setose lobe on the basal median gonocoxite is considered to be a volsella (in the sense of the volsella of the Thienemannimyia group in Murray & Fittkau, 1989) it would be the least developed volsella in the group. Treating Yarrhpelopia as excluded from the Thienemannimyia group, the tapering gonostylus, plain wing, bare eye, costa ending clearly before M1+2, absence of scutal tubercle and paired spurs present with outer half length of inner, leads to a cluster of genera in which wing venation is critical in further keying. The anterior wing venation is difficult to interpret due to weakly-indicated veins and dense setosity. However R1 and R4+5 are approximated especially in the male, and with R2+3 compacted between them and with R2 faintly detectable. Although these keys do not strongly follow phylogeny, and each stage differs in morphological proximity, adjacency to Zavrelimyia (Paramerina) recurs.

The following description includes features of taxonomic significance at generic level. Until further species are collected, the description of Yarrhpelopia norrisi sp.n. summarises features of a new genus.

Figures

FIGURE 1. Yarrhpelopia norrisi gen. n. sp. n. Adult male. A. Antennal apex; B. Wing; C. Tibial apices, TI – TIII L to R; D. Hypopygium, left side dorsal, right side stylised ventral / internal.

FIGURE 2. Yarrhpelopia norrisi gen. n. sp. n. Pupa. A. Thoracic horn and thoracic comb; B. Dorsal abdomen; C. Tergite IV spinulation (' shagreen'), detail; D. Anal lobe, left half.

FIGURE 3. Yarrhpelopia norrisi gen. n. sp. n. Larva. A. Head, left ventral, right dorsal: Abbreviations: S 5 - S 10 cephalic setae, DP—dorsal pit, VP—ventral pit: B. Segments 2 – 4 of antenna; C. Antennal apex; D. Mandible; E. Ligula; F. Palp; G. Submentum; H. Posterior parapod claws (selected).