The Landing Responses of Insects: I. The Landing Response of the Fly, Lucilia Sericata, and Other Calliphorinae

1. The leg movements and changes in the wing beat pattern which occur when the fly, Lucilia sericata , is in the proximity of a landing surface have been filmed and the sequence of events described in detail. 2. The legs are lowered from their retracted flight position as the result of a visual stimulus mediated by the compound eyes alone. 3. The moment at which the legs are lowered is not based upon an estimation by the fly of the distance between itself and the surface it is approaching. A normal landing response can be evoked merely by decreasing the light intensity of the surroundings without any movement occurring in the visual field. 4. The effective stimulus is based upon a multiplication of: the change of intensity at successive ommatidia when a fly approaches a landing surface, the number of ommatidia so stimulated and the rate of their successive stimulation. A given value of this product is required to evoke the landing response. 5. The landing responses of other Diptera and representatives of other insect orders have been described.