1. The cockroach Henschoutedenia epilamproides produces distinctive patterns of sound, on being disturbed, by means of a stridulatory apparatus. The carrier frequency of the sound is between 4.5 and 5.0 kcyc./sec., and is amplitude-modulated to form pulses. These pulses are grouped to form chirps, which are emitted singly or in a series. The structure of the longer chirps (50-100 msec.) may be quite complex.

2. While the circumstances under which sound is usually produced in the laboratory suggests that it is not important in intraspecific communication, it may be of some importance to the cockroach to hear its own sound. Recordings made from the cereal nerve show that the cockroach responds hardly at all to its own sound, and very poorly to artificial tones above 400 cyc./sec. The cercal afferents are most sensitive to tones of 50 cyc./sec, and will respond to less than 60 db. at this frequency.

3. Although the auditory performance of Henschoutedenia cercal receptors appears poor by comparison with Periplaneta americana, their responses to air movements are most striking. Some difficulty was experienced in standardizing this form of stimulation, but it appeared that Henschoutedenia was much more sensitive than Periplaneta to this form of stimulation.

4. Experiments with rodents (Rattus rattus and Clethrionomys glareolus) lent some support to the idea that the cockroach sound mimicked the cries of rodent predators, and had some deterrent effect on them.

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