Eurycorypha curviflava, Hemp, 2017

Heller, Klaus-Gerhard & Hemp, Claudia, 2020, Hyperdiverse songs, duetting, and the roles of intra- and intersexual selection in the acoustic communication of the genus Eurycorypha (Orthoptera: Tettigonioidea, Phaneropterinae), Organisms Diversity & Evolution (New York, N. Y.) 20 (4), pp. 597-617 : 602-603

Eurycorypha curviflava ( Figs. 3 , 4a , 6 , 8a , and 9a )

In the calling song of E. curviflava , three sound elements are found which were produced in homogenous series, in alternation or mixed ( Fig. 4a ). Besides short and long echemes (see below), the males made regularly long isolated syllables. Two of these elements occurred always in a fixed combination, considered basic unit of the song; the “short” echemes contained three to five syllables (4.3 ± 0.5; syllable period 74 ± 12 ms; SRR, 13.5 Hz; n = 6 males with 10 measurements each; T = ca. 20–23 °C). Within the syllables, the impulses were densely packed, and no intervals could be recognized. After an interval of 1.6 ± 0.3 s, they were followed by a long, isolated syllable (236 ± 51 ms) consisting of clearly recognizable impulses. The coefficient of variation for the interval was quite low, between 1.5 and 5.5% for the males recorded in the laboratory, and only in the field recorded male 10.2%. This basic unit could be repeated without any other sound between in intervals of several seconds. Often, however, two of these combinations were separated by “long” echemes. These sounds were typically softer than the basic unit and variable concerning the number of elements they consisted of. Without interruption, typically 11.7 ± 8.5 elements were observed (range, 3–40; period, 277 ± 35 ms), but quite frequently several of these echemes followed each other directly before the next short echeme was produced. The elements of the long echemes consisted typically of a few (mostly 3–5) impulse-like sounds, clearly separated from each other. Their period (29.8 ± 4.8 ms; repetition rate, 34 Hz) was so regular that for their production, a neuronal basis seems to be more likely than simple contacts of the scraper with neighboring teeth of the stridulatory file .

If two males were singing side by side without hearing a female response, they alternated on a long or short time scale. Sometimes, they produced their series during silent periods of the other male, separated from the other’ s song by long gaps (at least 90 s). However, they alternated also on a short time scale. In this case, they produced their long echemes preferentially during the silent intervals of the other ( Fig. 8a ).

The females responded to two male sound elements ( Fig. 6 ). Most answers occurred during the long echemes. Here, the females responded with a mean delay of 130 ms (seven series with ten measurements each of three females at different male-female distances) after the beginning of a syllable. They responded also to the single syllables, but the delay measured from the beginning of the syllable was larger than in the long echemes and more variable (mean delay of 238 ms in eight series with ten measurements each of three females at different male-female distances and to different males). Very often, the responses occurred before the end of the syllables and contained more groups of impulses ( Fig. 9 ) than responses to the long echemes. At a distance of 10 cm between the singers the mean delay was 182 ms (range, 144–221 ms; n = 3 series), at 50 and 200 cm, the mean delays were 270 and 274 ms, respectively (range, 235–320 ms; n = 5 series). At 200 cm distance, one of the females responded only to the single syllables but not in the long echemes. The females were not observed to respond to the short echemes except in three cases. Interestingly, here always a short impulse-like sound preceded directly the echeme and the response followed after this sound ( Fig. 9 ).

Figures

Fig. 3 Power spectra of male calling song of Eurycorypha species. In species with restricted frequency range, short black lines mark its end. Blue lines indicate power spectra of female responses

Fig. 4 a, b Oscillograms of male calling songs, overview (10 s sections)

Fig. 6 Oscillograms of male- female duets, overview (10 s sections)

Fig. 8 Oscillograms of long acoustical (1 min sections) interactions of a males in Eurycorypha curviflava and duets of males and females in b E. ligata, c E. pianofortis, and d E. pseudovaria

Fig. 9 Oscillograms of song interactions in Eurycorypha curviflava and E. ligata. a Male-female duet in E. curviflava, b, c Male-male interactions in E. ligata (6 s sections)