Tymbal - Cicadas
Cicadas produce their call in a remarkably different way to crickets. While cicadas do have wings they are not involved in any way in the production of their mating call, instead as mentioned they use a tymbal system (Gullan & Cranston, pp. 99-101, 2010). This gives the cicada a very different call then the cricket as well, as you can hear in the video below. This is because using the tymbal system gives the cicada variable modulated pulses rather than rasps (Gullan & Cranston, pp. 99-101, 2010).
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There are multiple sections that make up the tymbal and they include; the membrane or pad (this surround the ribs), the ribs, the plate and the tensor muscle (Gullan & Cranston, pp. 99-101, 2010). Sound is generated by distorting the membrane that surrounds the ribs thus sending vibration through the ribs, it is this vibration that produced the sound (Gullan & Cranston, pp. 99-101, 2010). The call is enhanced by the presence of the plate in the tymbal, the plate ‘rolls’ when the tensor muscles are contracted, this rolling movement results in the inward twisting of the ribs at the dorsal end, this deformation resonates the initial vibration back off the plate allowing the generation of the dominate frequency of 4 kHz (Young & Bennet-Clark, 1995). In Figure 4 the lay out of the tymbal can clearly be seen, the tymbal is found dorsally on the male cicada, there is one on each side of the first abdominal segment (Gullan & Cranston, pp. 99-101, 2010).
Figure 4: The lay out of the tymbal can clearly be seen here with the membrane (labelled frame here) covering the compartment that contains the plate, and ribs. As the muscles that are connected to the membrane contract the compartment inside becomes distorted, this distortion sends vibration through the ribs which generates the initial sound, however this is compounded as the plate 'rolls' as the ribs further distort too. This rolling causes the vibrations to resonate off the plate which enhances the sound that is generated, allowing the initial sound to come to 4kHz before amplification.
Amplification occurs due to specialised air sacks that cicadas have in their tracheal system (Gullan & Cranston, pp. 99-101, 2010). These air sacks work in a similar way to the subalar space in crickets as they both generate echoes to amplify the sound. Although the air sacks in the cicada do not alter the frequency of the sound at all it merely resonates it (Gullan & Cranston, pp. 99-101, 2010). This amplification of the call allows about a 3kHz increase bringing the total volume to a maximum of 7kHz, this allows the call to travels up to 1km even in dense forest (Gullan & Cranston, pp. 99-101, 2010).
Reception of this generated sound is the same in both the sexes. Sound is received through tympanic membranes that lie on the ventral side of the first abdominal segment (this is directly opposite the tymbal in the male cicada) (Gullan & Cranston, pp. 99-101, 2010).
Reception of this generated sound is the same in both the sexes. Sound is received through tympanic membranes that lie on the ventral side of the first abdominal segment (this is directly opposite the tymbal in the male cicada) (Gullan & Cranston, pp. 99-101, 2010).