Flight and hearing: ultrasound sensitivity differs between flight-capable and flight-incapable morphs of a wing-dimorphic cricket species

We studied frequency sensitivity of flight-capable and flight-incapable forms of the wing-dimorphic cricket Gryllus texensis, using both behavioral and neurophysiological measurements. Behavioral thresholds for negative phonotaxis in response to ultrasound stimuli are lower for long-winged (i.e. flight-capable) crickets than for short-winged (flight-incapable) individuals, whereas thresholds for positive phonotaxis in response to a calling-song model do not differ. Similarly, thresholds of the identified interneurons ON1 and AN2 differ between flight morphs for high sound frequencies but not for the frequency of calling song. Our results show that sensitivity to ultrasound is closely linked to flight ability, and thus to the risk of predation from aerially hawking bats. We suggest that sensitivity to ultrasound is one of a suite of flight-associated characteristics, the development of which may be under common hormonal regulation.