Activation of Echolocation Signal Emission by Noctuid Moths (Noctuidae, Lepidoptera) in Response to Retranslation of Echo-Like Stimuli

Noctuid moths (Noctuidae) are the only group of invertebrates for whom echolocation was demonstrated [2, 3]. The probing signals of these insects are short-wavelength ultrasonic clicks that are emitted during flight at a close to horizontal wing position. The maximum radius of the echolocation system sensitivity is 10 to 35 cm according to different a u hors [2-4]. Studies of the capability for echolocation in noctu id moths demonstrated no definite responses to echo [2 , 3]: the moths either flew toward the object discovered by echolocation or around it. Moreover, the motivation changed several times during the experiment. Such a variation in the insect's behavior introduced uncertainty into experimental results, and the problem of searching for more stable parameters arose for the moth's ability to respond to echo. Similar problems appeared and were then solved in studies of bat responses to model stimuli. The increase of emitted probing signals may be used as an indicator of an increased attention of bats to biologically important echolocation information [1]. These changes were reproducible and could be easily recorded. The question of how noctuid moths behave in similar situations arises. We suggested that echolocation stimulation induces a similar increase in the frequency of acoustic signals emitted by a noctuid moth. Here, we verify this suggestion. To record emitted signals, a moth was fixed on a long thin wire of a horizontal shift detector and stimulated with acoustic signals that simulated the echo of its own clicks. The scheme of the experimental setup is shown in Fig. 1. An amplified natural signal from the microphone output was transmitted to a computer-operated electronic switch. When the switch was turned on, each moth's click triggered a generator of echo-like stimuli. This scheme allowed