Auditory-evoked evasive manoeuvres in free-flying locusts and moths.
We presented free-flying locusts (Locusta migratoria L.) with sounds that varied in temporal structure and carrier frequency as they flew toward a light source in a flight room under controlled temperature and light conditions. Previous studies have shown tethered locusts react more often to trains of 30-kHz pulses than to pulse trains below 10 kHz. Further, this acoustic startle response has been suggested to function in bat-avoidance. We expected free-flying locusts to respond similarly; however, we found locusts responded to all sounds we presented, not just high-frequency, "bat-like" sounds. Response rates of turns, loops, and dives varied from 6% to 26% but were statistically independent of carrier frequency and/or pulse structure. Free-flying moths and tethered locusts were tested using a subset of our acoustic stimuli under the same temperature and light conditions as the free-flying locusts. Moth responses were carrier frequency dependent as were responses of tethered locusts positioned along the flight path observed in our free-flight trials. All responses were unaffected by a 90% reduction in room light. We conclude that locusts possess an acoustic startle response evocable in free flight, however, free-flying locusts do not show the same discrimination observed in tethered locusts under similar conditions.
Dawson
J W
JW
Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada. jwd30@cam.ac.uk
Kutsch
W
W
Robertson
R M
RM
D000161:Acoustic Stimulation / Q000379:methods*; D000818:Animals; D005260:Female; D005426:Flight, Animal / Q000502:physiology*; D006110:Grasshoppers / Q000502:physiology*; D008297:Male; D009036:Moths / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology