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Flight Activity in the Blowfly, Calliphora Erythrocephala, in Relation to Wind Speed, With Special Reference to Adaptation
1 Department of Biology, St Thomas's Hospital Medical School, London
1. A study has been made of the effect of wind speed on the flight activity of a population of the blowfly Calliphora erythrocephala in a small wind tunnel.
2. Under the experimental conditions wind has an activating effect up to about 0·7 m./sec., above which it inhibits flight.
3. Below 0·5 m./sec., activity decreases rapidly with decrease of wind speed and then remains at or close to the lower value. The increase of activity arising from increase of wind speed is much slower, the state of low activity tending to persist.
4. At speeds between 0·5 and 4·5 m./sec. the changes of activity in response to both increase and decrease of wind are very rapid and are followed by a considerable degree of adaptation in each case.
5. Inhibition of activity by the change of wind speed from 0·5 to 4·5 m./sec. and to 8·0 m./sec. results from the movement of the third antennal joint relative to the head.
6. When this antennal movement is prevented, the change to 4·5 m./sec. causes activation if the initial activity is low, and the change to 8·0 m./sec. causes an increase of walking activity although flight is decreased for mechanical reasons.
7. Exposure to the higher speeds causes an additional depression of activity not dependent on movement of the third antennal joint.
Submitted on April 18, 1958
