Timbal (biology)

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Timbal is a term for a vibrating membrane in the abdomen of a male cicada, which is responsible for the characteristic sound produced by the insect.

The paired timbals are located on the sides of the abdominal base. The "singing" of a cicada is not stridulation as in many other familiar sound-producing insects like crickets (where two structures are rubbed against one another): the timbals are regions of the exoskeleton that are modified to form a complex membrane with thin, membranous portions and thickened "ribs". These membranes vibrate rapidly, and enlarged chambers derived from the tracheae make the cicada's body serve as a resonance chamber, greatly amplifying the sound. Some cicadas produce sounds louder than 106 dB (SPL), among the loudest of all insect-produced sounds. They modulate their noise by wiggling their abdomens toward and away from the tree that they are on.