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Figure 2. A stridulating cricket (Eurepa sp.) in a figure that has been modified to highlight the location of the harp (magenta), plectrum (red), and file (yellow). Courtesy of Vicki Powys.
dinated with the resonance of the wing by an escapement mechanism whereby each cycle of wing vibration disengages the plectrum from the tooth against which it is apposed, al- lowing it to strike the next tooth on the file (Eliot and Koch, 1985). As a result, input from each tooth strike is phased so that it adds constructively to the ongoing vibration of the wing. A slow-motion video of stridulation (courtesy of F. Montealgre-Z) can be seen here: http://acousticstoday.org/ toceanicus.
The loudest known insect sounds are produced by cicadas. The sounds are generated by the distortion or buckling of a series of ribs that, together with the surrounding elastic material and an associated stiff plate, comprise each of the paired abdominal tymbals (Figure 3). Inward buckling of the tymbal is driven by the contraction of a powerful muscle that pulls the cuticular plate inward, and relaxation to the rest position is powered by the tymbal’s elastic components.
As each rib buckles in turn, it undergoes a damped vibra- tion with a resonant frequency near that of the male’s song. Similar to the coherent phases of successive tooth strikes of crickets, the buckling of successive ribs occurs in phase with ongoing vibrations when the energetics are presumably most favorable, thereby generating an essentially continuous tone at the dominant frequency of the song.
The tymbals are coupled to another resonant structure formed by a large air sac that nearly fills the male’s abdo- men and the closely associated eardrums. Together, the air
Figure 3. Top: location on a cicada’s body (head is to the left) of the left tymbal (arrow); left eardrum is highlighted in orange. Bottom: cuticular ribs (asterisks). Modified from Bennet-Clark (2007).
Figure 4. A mole cricket, Gryllotalpa vinaea, singing from his bur- row. From Bennet-Clark (1970).
sac and eardrums function as a Helmholtz resonator that is tuned to the male’s song frequency. Sound pressure within the air sac can reach the astonishing level of 158-dB SPL. The song, which is radiated through the large eardrums, can reach 100-dB SPL at 1 m.
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