Study

The role of the tymbal in cicada sound production

Young, David; Bennet-Clark, Henry C.

Journal of Experimental Biology, 1995

Peer-reviewedcontrolled laboratory experimentlaboratory

What they did

Sound output and tymbal movement were recorded simultaneously in singing cicadas, with the abdominal air sac and tymbal ribs experimentally manipulated, to establish how the sound is generated and amplified.

Studied in: Cyclochila australasiae
Sample size: high-speed recording and acoustic measurement of singing cicadas

What they found

Sound is produced by the buckling of a ribbed cuticular membrane — the tymbal — which clicks inward rib by rib as a muscle contracts, and clicks out again on release, each buckling producing a pulse. The largely hollow abdomen acts as a resonator tuned to the pulse frequency, radiating the sound efficiently. Output is among the loudest of any insect for its size.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Cicada song is produced by elastic buckling of the tymbal ribs and amplified by an abdominal resonator, a mechanism distinct from the stridulation used by crickets and grasshoppers.

How NatureHQ reads it

Worth being precise about, because almost every account of cicada noise describes it as rubbing, which is what crickets and grasshoppers do and what cicadas do not do at all. A cicada has a ribbed membrane that snaps inward like the lid of a jam jar, several hundred times a second, in a body that is mostly empty space acting as a resonator. That is why the sound is so loud from so small an animal, and why the abdomen is hollow — the insect is largely a loudspeaker with an insect attached.

Limitations

One large Australian species chosen for its convenient size; tymbal mechanics vary across the family.
Manipulations necessarily alter the structure being measured.
Neural control of the muscle is not addressed here.