On the So-called Constant-lift Reaction of Migratory Locusts

1. Locusts were fastened to a force transducer in front of a wind tunnel to measure their lift and thrust during tethered flight heading into the wind. The thrust measurement was used to adapt the wind speed to the flight speed of the animals. Thus, the locusts could choose their flight speed freely in the range 0.5–7ms−1. 2. At light intensities of about 0.02 lx (twilight), the locusts generally produced a maximum lift greater than 100% of their body weight. 3. A miniature motor mounted on the force transducer could alter the body angle of the locusts without further interference. Lift was found to be influenced by body angle. No ‘constant-lift reaction’ evoked by exteroceptive information of the aerodynamic flow was found. 4. Flight speed was almost independent of the imposed body angle. 5. Generally, a flight speed of about 3 m s−1 was necessary for level flight. There was no further correlation between lift and flight speed.