The tymbal (or timbal) is the corrugated exoskeletal structure used to produce sounds in insects. In male

cicada The cicadas () are a superfamily, the Cicadoidea, of insects in the order Hemiptera (true bugs). They are in the suborder Auchenorrhyncha, along with smaller jumping bugs such as leafhoppers and froghoppers. The superfamily is divided into tw ...

s, the tymbals are membranes in the abdomen, responsible for the characteristic sound produced by the insect. In tiger moths, the tymbals are modified regions of the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

, and produce high-frequency clicks. In lesser wax moths the left and right tymbals emit high frequency pulses that are used as mating calls. The paired tymbals of a cicada are located on the sides of the

abdominal The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso ...

base. The "singing" of a cicada is not

stridulation Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...

as in many other familiar sound-producing insects like

crickets Crickets are orthopteran insects which are related to bush crickets, and, more distantly, to grasshoppers. In older literature, such as Imms,Imms AD, rev. Richards OW & Davies RG (1970) ''A General Textbook of Entomology'' 9th Ed. Methuen 8 ...

(where one structure is rubbed against another): the tymbals are regions of the

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

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 enable the cicada's body to be a

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied Periodic function, periodic force (or a Fourier analysis, Fourier component of it) is equal or close to a natural frequency of the system ...

chamber, greatly amplifying the sound. Some cicadas produce sounds louder than 106

dB (SPL) Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophon ...

, among the loudest of all insect-produced sounds. They modulate their noise by positioning their abdomens toward or away from the substrate. The tymbals of a tiger moth are specialized regions on the metathoracic episterna, normally corrugated such that sound is produced when the entire tymbal surface is buckled by muscular contraction and then released, producing a series of extremely rapid "clicks" as the corrugations flex back into place. These sounds are only occasionally audible to humans, and are used in both acoustic aposematism (the moths are advertising to bats that they are toxic), and as mating signals. A recent study demonstrates that these sounds are used by some moths to "jam" the sonar of moth-eating bats.Fullard, J.H., M.B. Fenton, and J.A. Simmons (1979) Jamming bat echolocation: The clicks of arctiid moths. Can. J. Zool. 57: 647-649

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External links

* {{cite EB1911, wstitle= Hemiptera , volume= 13 , last= Carpenter , first= George Herbert , author-link= George Herbert Carpenter , pages = 258–262 Insect anatomy