Ewartia thamna Popple, 2017, n. sp.

Ewartia thamna n. sp.

(Plates 2C, 2D; Figs 2 E, 8E, 24B, 29C, 30)

Types. Holotype: ♂ [typed] ‘ Australia NT’ / ‘AU.NT.MTE 76 km E of Mataranka’ / ‘ 14°54.888’S 133°42.780’E’ / ‘ 77m 3 Feb. 2006 ’ / ‘Hill, Marshall, Moulds’ (NTM); Paratypes: ♀ same data as holotype (NTM); 1♂ 1♀ same data as holotype (QM); 2♂ same data as holotype (AE); 2♂ same data as holotype (LWP); 21♂ 2♀ same data as holotype (MSM).

Etymology. Latinised from the Greek word thamnos, meaning shrub. The name reflects the occurrence of the species in low, shrubby habitats.

Description. Male (Plate 2C; Figs 2 E, 8E, 24B).

Head (including eyes) approximately as wide as mesonotum; ventral surface mainly pale green to pale yellowbrown; postclypeus and anteclypeus green to pale brown; rostrum pale brown anteriorly, becoming dark brown towards apex; dorsal surface entirely pale green to yellow-brown; ocelli pink; with scattered silver pubescence throughout and long silver pubescence behind eyes. Eyes faded to brown in preserved specimens. Antennae dark brown.

Thorax with scattered silver short pubescence. Pronotum pale green to yellow-brown throughout; pronotal collar mainly green to pale green, yellow-brown medially. Mesonotum pale green to pale brown, with a narrow brown midline extending posteriorly from between the submedian sigilla to the posterior margin; submedian and lateral sigilla yellow-brown, subtle; cruciform elevation brown; wing grooves and metanotum yellow-brown, with silver long pubescence.

Legs with coxae and femora pale green to pale yellow-brown; tibiae pale green to pale yellow-brown; tarsi pale brown becoming darker towards apex of claws.

Wings with fore wing costal veins pale green to pale yellow-brown; pterostigma pale brown to brown; basal membranes orange; veins CuA, CuP and M green to pale brown; other veins brown; with eight apical cells. Hind wing veins pale brown or pale green, becoming darker on the posterior side of the apical cells; plaga surrounded by white and pale brown coloration anteriorly, otherwise transparent; with six apical cells.

Opercula broadly rounded, pale green to pale brown, with plates relatively flat.

Timbals with five long ribs; short (intercalary) ribs present between each long rib. Long ribs 1–3 attached to basal spur. Long rib 4 comparatively shorter. Long rib 5 narrow and short. All ribs sclerotised, pale and of very low contrast against timbal membrane.

Abdomen. Tergites mainly pale green to olive-brown, often yellow-brown along lateral posterior margins; darker midline coloration> 1 mm wide, approximately as wide as midline on mesonotum, brown, tending yellowbrown dorsolaterally. Sternites pale green to yellow-brown.

Genitalia. Pygofer, including dorsal beak, pale green to yellow-brown; upper lobes prominent, with apices rounded; basal lobes in lateral and ventral views broadly rounded. Uncus pale brown, in lateral view extended with apex rounded; claspers prominent with posterior section dark and outwardly curved, with apices broadly rounded ventrally. Aedeagus with pseudoparameres extending well beyond theca; endotheca fleshy; ventral support not extending to the same extent as endotheca.

Female (Plate 2D).

Markings and coloration identical to male. Abdominal segment 9 green to olive-brown, with a brown midline; ovipositor sheath extends <0.5 mm beyond termination of this segment.

Measurements. N= 10♂ 2♀. Means and ranges (in parentheses), mm; BL ♂ 13.9 (12.7–14.8), ♀ 16.9 (16.4– 17.3); FWL: ♂ 17.5 (16.1–19.1), ♀ 19.6 (19.0–20.1); FWW: ♂ 5.9 (5.5–6.6), ♀ 6.7 (6.6–6.8); HW: ♂ 4.1 (3.7– 4.4), ♀ 4.4 (4.3–4.5); PW: ♂ 4.1 (3.7–4.5), ♀ 4.4 (3.9–4.8); AW: ♂ 4.5 (4.0–4.7), ♀ 4.2 (3.8–4.5).

Distinguishing features. Ewartia thamna n. sp. is distinctive in appearance relative to other species in the genus. It is a relatively uniform green to yellow-brown cicada, with a narrow, brown, dorsal stripe, which extends medially posteriorly from the centre of the mesonotum to the apex of the abdomen (Fig. 2 E). In overall appearance, it is most similar to E. cuensis, which lacks the dorsal stripe entirely. It can also be distinguished readily from the remaining species in the genus by its narrow head width (3.5–4.5 mm; c.f.>5.0 mm for E. brevis, E. carina n. sp., E. etesia n. sp., E. lapidosa n. sp., E. oldfieldi and E. roberti n. sp.).

Distribution and habitat. Ewartia thamna n. sp. is described from a single locality at the southern edge of the Top End of the Northern Territory, some 76 km east of Mataranka (Fig. 25). Adults were found in low bushes and in grass in dry open shrubland on weathered sediments. Specimens have been collected in early February.

The distribution of E. thamna n. sp. overlaps with E. etesia n. sp. and both species have been collected at the same site (the type locality of E. thamna n. sp.).

Calling song. The only available recordings of E. thamna n. sp. made by David Marshall and Kathy Hill (n=5) do not appear to contain a definitive simple calling song mode. Due to this limitation, only the complex calling song mode is described here. This calling song mode (Fig. 30) contains a sequence of 5–12 syllables (each 0.010– 0.012 s duration) or short macrosyllables (each comprising 2 syllables, 0.021– 0.027 s duration), each separated by a gap of 0.033– 0.144 s duration. This is followed by a shorter sequence of 3–5 of the short macrosyllables separated by a shorter gap of 0.008– 0.044 s duration. The subphrase then either concludes with a gap of 0.051– 0.114 s duration or proceeds rapidly to the accentuation. The accentuation comprises a single long macrosyllable or short echeme (0.052– 0.127 s duration) followed by a gap of 0.063– 0.168 s duration.

Some interruptions are apparent in a few passages of successive subphrases that do not contain the accentuation, which may indicate a potential transition to a simple calling song component. These interruptions are formed by an atypically large gap of up to 0.327 s, typically occurring after the third syllable in the initial syllable sequence of each subphrase.

The calling song exhibits no apparent change in frequency spectra between song modes. In each mode the calling song typically has a highest amplitude frequency plateau between 12.0 and 19.1 kHz, with a dominant frequency between 15.7 and 16.3 kHz (mean=16, n =3; e.g. Fig. 29 C). As a consequence, the call is higher pitched than other examples in the Ewartia oldfieldi species complex. This includes E. etesia n. sp., which has been found at the same location as E. thamna n. sp. (Fig. 25), and produces a calling song with a similar temporal structure (cf. Figs 26, 27 with Fig. 30).