Sound Production And Reception

Cicadas are best known for their ability to produce loud sound. No other insect has developed such an effective and specialized means of doing so. The calls are mating songs produced only by the males. Each species has its own distinctive song and attracts only females of its own kind (Fig. 2).

The organs of sound production are the tymbals, a pair of ribbed cuticular membranes located on either side of the first abdominal tergite (Fig. 3). In many species the tymbals are partly or entirely concealed by tymbal covers, platelike anterior projections of the second abdominal tergite. Contraction of internal tymbal muscles causes the tymbals to buckle inward, and relaxation of these muscles allows the tymbals to pop back to their original position. The sound produced is amplified by the substantially hollow abdomen, which acts as a resonator.

Many species sing during the heat of the day, but some restrict their calling to semidarkness at dusk. Often the species that sing at dusk are cryptic in coloration and gain further protection from predatory birds by confining their activity to dusk. The loud noise produced by some communal day-singing species actually repels birds, probably because the noise is painful to the birds' ears and interferes with their normal communication. The American periodical cicadas

FIGURE 2 A mating pair of northern cherrynose, Macrotristria sylvara (family Cicadidae). This large and colorful species is found in tropical northeastern Australia. (Photograph by Max Moulds.)

FIGURE 3 Transverse section of male abdomen of Tamasa tristigma at the first abdominal segment with the thorax removed. Exposed are the large tymbal muscles anchored basally to a chitinous V and attached dorsally via an apodeme to the sound-producing tymbals. Sound received by the tympana is transferred to the auditory capsules.

FIGURE 3 Transverse section of male abdomen of Tamasa tristigma at the first abdominal segment with the thorax removed. Exposed are the large tymbal muscles anchored basally to a chitinous V and attached dorsally via an apodeme to the sound-producing tymbals. Sound received by the tympana is transferred to the auditory capsules.

have mass emergences, and although their song is not sufficiently loud to repel birds, the number of individuals is so large that predatory birds soon lose their appetite for them.

Both sexes have organs for hearing. Sound is received by a pair of large, mirrorlike membranes, the tympana, which are often concealed below the opercula (Fig. 3). The tympana are connected to an auditory organ by a short slender apodeme. A singing male creases the tympana to avoid being deafened by his own song.

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