Moth ears

Moth has two ears which are situated just below the hind wings, at the metathorax. They are called tympanic organs.

Anatomically, the ears of moths are considered to be among the simplest ears found in animals. Each tympanic organ has a drum-like membrane and two auditory receptor cells attached to the center of the membrane, which are called A1 and A2 cells. Some moths have only one instead of two receptor cells per ear. Each ear also includes one more neuron, the B cell, which is not an auditory receptor.

All the neurons fro an ear enter the central ganglia ehrough the tympanic nerve.

The spectral sensitivity of an ear is determined mostly by the tympanic membrane and its resonant frequency. Taking into account the number of receptors in the ear it was generally beleived that moths are tone-deaf (Suga, 1961; Roeder, 1974). Numerous electrophysiological experiments supported this belief.

Latest experiments (Lapshin, Vorontsov, 2003; Windmill et al., 2006) evidence that the membrane mechanics is also quite complex compared to a simple drum and that frequency tuning is possible.

References

Eggers F. (1919) Das thoracale bitympanale Organ einer Gruppe der Lepidoptera, Heterocera // Zool. Jb. (Anat.) V.41. P.273-376.

Treat A.E., Roeder K.D. (1959) A nervous element of unknown function in the tympanic organs of moths // J. Insect. Physiol. V.3. 2. P.262-270.

Roeder K.D. (1966b) Interneurons of the thoracic nerve cord activated by tympanic nerve fibres in noctuid moths // J. Insect. Physiol. V.12. P.1227-1244.

Surlykke A., Miller L.A. (1982) Central branchings of three sensory axons from a moth ear (Agrotis segetum, Noctuidae) // J. Insect. Physiol. V.28. N4. P.357-364.

Suga N. (1961) Functional organization of two tympanic neurons in noctuid moths // Jpn. J. Physiol. V.11. P.666-677.

Roeder K.D. (1974) Responses of the less sensitive acoustic sense cells in the tympanic organs of some noctuid and geometrid moths // J. Insect. Physiol. V.20. P.55-66.

Lapshin D.N., Vorontsov D.D. (2003) Frequency retuning of tympanic organ of noctuid moth (Noctuidae, Lepidoptera) // Sensornye systemy, V.17, 3, P.223-230. (in Russian).

Windmill J.F.Ch., Jackson, J.C., Tuck E.J., Robert D. (2006) Keeping up with bats: dynamic auditory tuning in a moth // Current Biology, V. 16, P. 2418-2423.