ECHOLOCATION IN NOCTUID MOTHS (LEPIDOPTER A, NOCTUIDAE)

The adaptive significance of ultrasonic clicks emitted in flight by no ctuids was studied. Three series of experiments have been performed. I n the first one the ability of moths to discriminate between their own clicks and their echo had been studied (fig. 1)). The results have sh own that noctuids can distinguish between their own signals and artifi cial echo-like stimuli following the clicks with delay of 0,2 ms (fig. 3). In the second series of tests we examined the capability of flyin g moths glued to a thin flexible wire to avoid artificial obstacles in complete darkness (fig. 2;. We recorded the number of contacts with t wo types of corner reflectors. One of the reflectors had the coefficie nt of ultrasound reflection at frequencies above 40kHz two times as hi gh as another one. Moths with intact auditory organs were found to be more capable to avoid collisions with obstacles of higher ultrasound r eflection (fig. 4). Perforation of the tympanal membrane resulted in l oss of the ability to discriminate between two types of reflectors. In the third series of experiments the correlation between the length of the periods of sound emission and the number of moths colliding with two types of spherical reflectors was studied. Flying moths emitting t he sound were able to avoid obstacles having higher ultrasound reflect ion, while during the flight whithout clicks the number of contacts wh ith both types of reflectors was approximately equal (fig. 5). These r esults suggest that some of noctuid moths can use echolocation for ori entation in flight.