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NEUROBIOLOGY NEUROBIOLOGY Ch. 19 Ch. 19 MECHANISMS OF ESCAPE BEHAVIOR MECHANISMS OF ESCAPE BEHAVIOR Night-flying moths, or noctuids, have a tympanic membrane that stretches over an enclosed ear sac which is located in the insect’s abdomen. In the tympanic membrane, there are two sensory (acoustic) neurons called A1 and A2. Both of these neurons are sensitive to sound frequencies from 40 to 70 kHz. This is the same frequency of most bat cries. Kenneth Roeder, the father of neuroethology, did studies to show how the moth avoidance response is mediated by the moth nervous system. On page 447, Kenneth Roeder recorded the responses of the acoustic neurons A1 and A2 in noctuids as they heard cries from bats. Summary: A1 is sensitive when the bat is 100-120 feet away A2 is less sensitive than A1. It begins to respond as the bat gets closer. A1 and A2 fire at the maximum rate when the bat is 15-20ft away. In the figure, T represents the moth. M1 and M2 are speakers. Because noctuids have two ears, one on either side of the abdomen, the intensity of the cry is lower on the side of the abdomen opposite of the bat. This is because the abdomen deflects the sound waves. By computing the strength of the responses from both ears, the moth determines the direction of the bat. In a separate study on page 448, Roeder studied avoidance responses of moths to pre-recorded bat cries. Summary:
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This note was uploaded on 04/16/2008 for the course BIOL 317 taught by Professor Kawasaki during the Fall '07 term at UVA.

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