Morphological and acoustical study of the sound-producing mechanism in noctuid moths was carried out on Amphipyra perflua F. There are two laterally symmetrical pairs of adjacent to each other complementary areas - one is situated on the ventral surface of the base of the forewing, the other one is on the metascutum. The surface of these areas is covered with cone-like structures (aculeae) of 18-25 mkm in height. The density of aculeae reaches 3 per 100 mkm². The aculeae of complementary areas are oriented towards each other and can serve as a coupling mechanism between wings and metascutum. While uncoupling, these structures produce ultrasonic pulse. Moths with these structures removed are not capable of emitting clicks. Noctuid moths produce ultrasonic clicks during flight. Peak amplitude of these clicks varies from 70 to 84 dB SPL in 5 cm from the moth, mean duration is 67 mks. Clicks have a broad-band (more than 100 kHz) spectrum with main peaks at 57 and 78 kHz. Artificially generated clicks have similar spectrum. The regular pattern of emission with one click per every second or every third wingbeat was often observed in the condition of tethered flight and naturally. The adaptive meaning of peculiarities of the moths' acoustic behavior is discussed.
PDF

Morphology of click emission mechanism	Oscillograms and spectra of the moth clicks	Variability of acoustic   spectra	The directivity diagram of acoustic emission
85 kb	56 kb	87 kb	63 kb

Position of moth's wings at the moment of click emission	Detecting ultrasonic clicks under natural conditions	Examples of the series of clicks	The dynamics of acoustic emission
32 kb	52 kb	13 kb	18 kb