Bioacoustics of Illyria viridis

Measurements. Range and mean (in mm) for 10 males , 9 females (includes smallest and largest specimens). Length of body (including head): male 15.6–17.3 (16.2); female (including ovipositor) 14.8–18.7 (16.5). Length of forewing : male 18.6–22.6 (20.6); female 17.7–20.5 (19.2). Width of head (including eyes): male 5.1–5.7 (5.4); female 4.8–5.5 (5.2). Width of pronotum (across lateral angles): male 5.6–6.2 (6.0); female 5.1–6.1 (5.8). Distinguishing features. Illyria viridis sp. n. is closest to I. hilli in its overall green appearance and markings, and has somewhat similar male genitalia. It differs, however, in having the distal ends of the veins forming the apical cells each bearing an infuscated spot, in its distinctly swollen male abdomen and very large tympanal cavity the occupies half the length of the abdomen. Song ( Figs 23a–d ). Recordings were examined only from the WA.DRK paratype location. The male calling song is a continuous, slightly rattle-like call. Short syllables of generally 3–8 pulses are produced at a uniform rate of 23–27 syllables/s. The song oscillates between series of syllables of contrasting length, with syllable length slowly decreasing with a concordant drop in amplitude and then more suddenly returning to longer, louder syllables. The resulting phrases are about 4.5–7 s in duration. Occasionally, just as the shift to longer, louder syllables begins, short single pulses are produced between the syllables. Peak sound frequency varies slightly between 10–11.5 kHz, with a drop in the dominant frequency corresponding to the transition to longer syllables. Most sound energy is concentrated within the range 9.0–12.5 kHz. Sound intensity varies by a factor of 2 to 3 on the oscillogram scale. Males sing both during the heat of the day and at dusk. Adults can often be plucked from grass stems while singing.