Typophyllum spurioculis

behaviour · bio.acousti.ca

3.2. Bioacoustics The description of the song is based on the recording of the call of a single male specimen collected in Ucumarí Colombia, and five males from Santa Lucía, Ecuador. 3.2.1. Colombian specimen One male was recorded indoors at a temperature of 23 ◦ C, rather high relative to common field temperatures. This male produced three bouts of sibilant four-pulse calls, each comprised of two syl- lables. In T. spurioculis, each syllable consists of two pulses, one produced during the opening stroke of the wing and the other during the closing (Fig. 4A). Here, syllables are therefore equiva- lent to what other authors term phonatomes, and a call of several phonatomes is in turn equivalent to a chirp or verse (compare e.g. Jatho et al., 1994; Stumpner and Meyer, 2001; Walker and Dew, 1972). Five to six calls were given in 3–6 s with bouts separated by silence of 17–18 s. Mean call duration for this male was 95 ms (n = 13). There is a consistent pause before the concluding pulse, which usually begins more abruptly. Mean values for the dura- tion of the four high-amplitude pulses in two calls were 23.3, 17.6, 12.3, and 34.3 ms respectively. The waveform (Fig. 4C) shows the characteristic pattern of two harmonically-related subequal carrier frequencies. The call is easily heard by a human ear, being almost entirely in the audio range (Fig. 4E). There are two harmonically related spectral peaks of comparable intensity. The more intense is near 12.1 kHz while its potential fundamental, 6.8 kHz, is slightly suppressed (mean values for n = 13 calls, FFT calculated over the whole of each song). 3.2.2. Ecuadorean specimens Five males from Ecuador were recorded at 17 ◦ C under field conditions using a portable recorder. From this group, two males were also recorded in laboratory conditions at 19 ◦ C in Santa Lucía, Ecuador using the same device. Males of this population also pro- duced groups of calls, each group consisting of four or five calls (each call containing two syllables), and groups are separated by silent intervals of 18.2 ± 4.2 s (Mean ± SD, n = 5, average measured from six random silent intervals of one recording of each male, for a total of 30 calls, Fig. 5A). From field recordings, specimens delivered 3–4 calls in 10 s; a similar pattern was maintained under lab conditions only when more than two males interacted acous- tically. Isolated singing males produced a more sporadic pattern, sometimes producing one call per minute. The average duration of one call (two syllables) of the Ecuadorian males was 117.6 ± 7.1 ms (n = 5, 7 calls randomly selected from each male, and averaged, Figs. 4B and 5C). The mean pulse duration of the high amplitude pulse was 31.6 ± 3.6 ms (Figs. 4B and 5C). The waveform of the pulse also shows similar characteristics to that of the Colombian male, with two dominant frequencies harmonically related (Fig. 4D). The major syllable pulse contains 160–170 oscillations. As measured in the Colombian specimen, the call of the Ecuadorean males also shows two consistent spectral peaks of comparable intensity that are harmonically related. The most intense peak was measured at 13.9 ± 2.2 kHz (n = 5, 1 random call per male) and its fundamental occurs at 7.0 ± 1.2 kHz (Fig. 4F). Analysis of frequency in time shows an unusual frequency modulation (FM) pattern of the two pulses in each syllable. The FM occurs periodically between 6.3 and 7 kHz, and this is more pronounced in the first syllable of the group (Fig. 5). Sound Pressure Level (SPL) measured across males in lab condi- tions was 98.2 ± 2.9 dB (re 20 Pa; root mean square over recorded songs with calibrated microphone at 10 cm dorsal from the singing male). 3.3. Wing resonances Five male specimens were used for LDV experiments. Both LW and RW were stimulated with broadband sound and wing reso- nances obtained by scanning the wing surface using LDV. These recordings show that only the right mirror plays a major role in sound radiation, while the equivalent left sound-radiating field is highly damped to vibrations (Fig. 6A–F). Within individuals the mirror shows three modes of vibration at around 6.8 ± 0.7 kHz, 13.5 ± 1.5 kHz, and 16.6 ± 1.9 (n = 5 individual averages of 120–130 scanned points in each mirror). Fig. 6G shows average FFT spectrum across the five males. The observed resonances of 11.3–16.6 kHz are within the range of carrier frequencies measured across specimens. During the same experiments we also studied the resonances of the entire wings using broadband stimulation (Fig. 7). We divided the wings in broad regions, represented by numbers in Fig. 7A. Region 1 in the middle of the costal field, region 2 radial/middle field, region 3 wing apex, and region 4, the stridulatory field. Although regions 1–3 vibrate with lower amplitude than the right stridulatory field, both wings show components of the resonances observed in the mirror of region 4 (∼7, and 10 kHz, ranges observed across five individuals), as well as those frequencies observed in the calling song in these ranges. The resonant peaks are variable within this range across individuals, but all of them show a common resonant peak between at 10 and 11 kHz, as illustrated in Fig. 7E–H.

this account at bio.acousti.ca