The paired stridulatory organs of a female.

<p>(a) A file (red arrow) is situated at the left anterior angle of the mesonotum. (b) A file (red arrow) is situated at the right anterior angle of the mesonotum. (c) A micrograph of a stridulatory file. (d) The red arrow indicates the scraper of a stridulatory organ. (e) A scanning electron micrograph showing the ridges of a file. (f) A scanning electron micrograph showing the scraper of a stridulatory organ.</p

A female of <i>Subpsaltria yangi</i>.

<p>Scale bar, 1 cm.</p

Stridulatory Sound-Production and Its Function in Females of the Cicada <i>Subpsaltria yangi</i>

<div><p>Acoustic behavior plays a crucial role in many aspects of cicada biology, such as reproduction and intrasexual competition. Although female sound production has been reported in some cicada species, acoustic behavior of female cicadas has received little attention. In cicada <i>Subpsaltria yangi</i>, the females possess a pair of unusually well-developed stridulatory organs. Here, sound production and its function in females of this remarkable cicada species were investigated. We revealed that the females could produce sounds by stridulatory mechanism during pair formation, and the sounds were able to elicit both acoustic and phonotactic responses from males. In addition, the forewings would strike the body during performing stridulatory sound-producing movements, which generated impact sounds. Acoustic playback experiments indicated that the impact sounds played no role in the behavioral context of pair formation. This study provides the first experimental evidence that females of a cicada species can generate sounds by stridulatory mechanism. We anticipate that our results will promote acoustic studies on females of other cicada species which also possess stridulatory system.</p></div

Acoustic playback stimuli.

<p>(a) Oscillogram of a part of stimulus ABC. (b) Detailed oscillogram of a female sound marked by the box in <i>a</i>. (c, d, and e) Detailed oscillograms of a modified female sound included in stimulus A, B, and C, respectively. (f, g, and h) Detailed oscillograms of a modified female sound included in stimulus AB, AC, and BC, respectively.</p

Scraper-ablation experiment.

<p>(a) The red arrow indicates one of the paired stridulatory organs of a female. (b) The red arrow indicates that the scraper of the stridulatory organ was removed.</p

Efficiency of the seven acoustic stimuli in eliciting behavioral responses from males.

<p>(a) Males’ phonotactic responses to different types of acoustic stimuli. Different letters indicate a significant difference (<i>P</i> < 0.05). (b) Males’ acoustic responses to different types of acoustic stimuli. Different letters indicate a significant difference (<i>P</i> < 0.05).</p

The sound-producing structures of <i>K</i>. <i>caelatata</i>.

<p>(a, b, c) Ventral, dorsal, and lateral view of a male with red box indicating the operculum involved in sound production. (d) Right red arrow marks the wing-holding groove of a male with right wing spread; left red arrow indicates that the basal posterior margin of the forewing is fixed in the wing-holding groove. (e) The forewing costa is supported over the operculum (red arrow).</p

Reflectance-based classification of independent validation data acquired from forewing costa.

<p>Reflectance-based classification of independent validation data acquired from forewing costa.</p

How Do “Mute” Cicadas Produce Their Calling Songs?

<div><p>Insects have evolved a variety of structures and mechanisms to produce sounds, which are used for communication both within and between species. Among acoustic insects, cicada males are particularly known for their loud and diverse sounds which function importantly in communication. The main method of sound production in cicadas is the tymbal mechanism, and a relative small number of cicada species possess both tymbal and stridulatory organs. However, cicadas of the genus <i>Karenia</i> do not have any specialized sound-producing structures, so they are referred to as “mute”. This denomination is quite misleading, as they indeed produce sounds. Here, we investigate the sound-producing mechanism and acoustic communication of the “mute” cicada, <i>Karenia caelatata</i>, and discover a new sound-production mechanism for cicadas: i.e., <i>K. caelatata</i> produces impact sounds by banging the forewing costa against the operculum. The temporal, frequency and amplitude characteristics of the impact sounds are described. Morphological studies and reflectance-based analyses reveal that the structures involved in sound production of <i>K. caelatata</i> (i.e., forewing, operculum, cruciform elevation, and wing-holding groove on scutellum) are all morphologically modified. Acoustic playback experiments and behavioral observations suggest that the impact sounds of <i>K. caelatata</i> are used in intraspecific communication and function as calling songs. The new sound-production mechanism expands our knowledge on the diversity of acoustic signaling behavior in cicadas and further underscores the need for more bioacoustic studies on cicadas which lack tymbal mechanism.</p></div

Forewing costas and average reflectance profiles of the 12 species included in this study.

<p>(a) Average reflectance profiles. Scale bar for all panels in (a) = 1 cm. (b) Average reflectance profiles. The dots in (b) denote the 23 location of the spectral bands selected for the classification of difference between non-mute and mute cicadas.</p