SUMMARYField observations on low‐flying gynoparae of Myzus persicae showed a marked upwind bias of courses in wind speeds between about 0.2 and 1.2 m/s, and of tracks of up to about 0.8 m/s. Progress over the ground was small and the net effect of the upwind bias was loose station‐keeping.Quantitative recordings from Aphis fabae virginoparae in a laboratory wind tunnel 1.2 × 0.9 m in section showed similar station‐keeping behaviour in winds up to about 0.4 m/s. The behaviour comprised upwind orientation and regulation of airspeed according to the wind speed, both reactions being more precise at higher wind speeds.These reactions to wind could be simulated in still air by providing a moving floor pattern. Their role in the field appears to have been underestimated.

Abstract. 1. The terminal velocities of freshly anaesthetized and weighed, virginoparous alatae were measured by dropping them into updrafts of known speed. For an average specimen weighing about 0.49 mg the terminal velocity was 1.78 ms‐1 with wings closed and 0.82 ms‐1 with wings fully extended horizontally.2. Extrapolating from the known terminal velocities of falling spheres of appropriate density, it is concluded that for inertly falling insects of constant shape the terminal velocity will be substantially lower with the wings extended than with them closed for all sizes of insect and that the horizontal distance travelled during a fall will be correspondingly greater.3. Sudden reflex immobilization and falling was sometimes observed in aphids flying in a laboratory flight chamber, and very occasionally this immobilized state was maintained for many seconds (even during handling) before recovery and renewed flight. There was no evidence of a special falling attitude (‘Fall‐reflexhaltung’) other than a simple ‘frozen flight’ attitude with wings extended horizontally and legs extended fore and aft while the insect spiralled downwards, abdomen first.4. The flying aphid's usual response to a coloured surface below it in the flight chamber was not to cease wing‐beating and fall but to fly downwards, abdomen first, at speeds up to more than 0.7 m s‐1.

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