Bioacoustics of Myopsalta xerograsidia

Distribution, habitat and behaviour ( Fig. 28 ). Myopsalta xerograsidia is the most widespread species in the genus, being found from southern Queensland ( Surat ) north to drier coastal and subhumid inland areas to Cape York and west to through much of the Northern Territory (though avoiding the humid Top End and the arid far south) to the Kimberley region, with an isolated population in the Pilbara of Western Australia . Populations occur in open grassland, grassy woodland, roadsides and river channels where the adults are typically found on low vegetation, particularly in grass. Adults have been encountered between September and May. Calling song ( Figs 34 , 35 ). This species exhibits a high-pitched, ‘reeling’ song, with a distinct build-up and variable phrase duration. Each phrase is composed of an introductory syllable or syllable sequence followed by a series of 2–10 subphrases (all statistics, n =62 recordings). On infrequent occasions only a single subphrase is produced. The introductory syllable sequence contains a series of 1–10 (rarely up to 18) syllables (0.005– 0.011 s duration) separated by successively decreasing gaps (0.005– 0.057 s duration), with a total duration of 0.014– 0.354 s . In some instances, the introductory syllable sequence is omitted and the phrase commences abruptly the first subphrase. Each subphrase comprises a long echeme (0.043– 0.152 s ) followed by a long syllable sequence with gaps of 0.004– 0.017 s between each syllable and a total duration of 0.080– 0.695 s . The final subphrase of each phrase typically exhibits a more condensed syllable sequence, with gaps between each syllable of 0.002– 0.020 s and an extended total duration of 0.096– 2.559 s . This is followed by a gap of 0.012– 0.041 s , a short echeme of 0.019– 0.052 s and a longer gap of 0.023– 0.161 s duration. It is expected that the female would respond during the long gap following the short echeme; however this interactions has not yet been recorded in this species. Occasionally, the gap at the end of the final subphrase is interrupted by an additional syllable. The calling song is produced with a persistent level of amplitude throughout. It also maintains an even frequency distribution, without apparent modulation, exhibiting a high amplitude plateau within the bounds of 11.6 and 17.8 kHz, typically 12.1–16.2 kHz. The song recordings of this species show remarkably consistent structure considering the widespread distribution of this cicada, a phenomenon noted for some other arid zone cicadas including Arenopsaltria nubivena (Walker) ( Ewart et al. , 2015a ) and Simona erema Ewart, Popple and Marshall (Ewart et al. , 2015b) . The most notable anomaly is present in the recordings from near Alice Springs, which differ in that the syllable sequences within each subphrase exhibit successively decreasing gaps between each syllable. This trait is not present in the recordings from populations further to the east.

Calling song (Figs 34, 35). This species exhibits a high-pitched, ‘reeling’ song, with a distinct build-up and variable phrase duration. Each phrase is composed of an introductory syllable or syllable sequence followed by a series of 2–10 subphrases (all statistics, n =62 recordings). On infrequent occasions only a single subphrase is produced. The introductory syllable sequence contains a series of 1–10 (rarely up to 18) syllables (0.005–0.011 s duration) separated by successively decreasing gaps (0.005–0.057 s duration), with a total duration of 0.014–0.354 s. In some instances, the introductory syllable sequence is omitted and the phrase commences abruptly the first subphrase. Each subphrase comprises a long echeme (0.043–0.152 s) followed by a long syllable sequence with gaps of 0.004–0.017 s between each syllable and a total duration of 0.080–0.695 s. The final subphrase of each phrase typically exhibits a more condensed syllable sequence, with gaps between each syllable of 0.002–0.020 s and an extended total duration of 0.096–2.559 s. This is followed by a gap of 0.012–0.041 s, a short echeme of 0.019–0.052 s and a longer gap of 0.023–0.161 s duration. It is expected that the female would respond during the long gap following the short echeme; however this interactions has not yet been recorded in this species. Occasionally, the gap at the end of the final subphrase is interrupted by an additional syllable. The calling song is produced with a persistent level of amplitude throughout. It also maintains an even frequency distribution, without apparent modulation, exhibiting a high amplitude plateau within the bounds of 11.6 and 17.8 kHz, typically 12.1–16.2 kHz. The song recordings of this species show remarkably consistent structure considering the widespread distribution of this cicada, a phenomenon noted for some other arid zone cicadas including Arenopsaltria nubivena (Walker) (Ewart et al., 2015a) and Simona erema Ewart, Popple and Marshall (Ewart et al., 2015b). The most notable anomaly is present in the recordings from near Alice Springs, which differ in that the syllable sequences within each subphrase exhibit successively decreasing gaps between each syllable. This trait is not present in the recordings from populations further to the east.