The fly's optomotor response to transient stimuli was studied under open loop conditions. The stimuli used were moving edges and stripes. A comparison of the fly's responses to these stimuli bends to the result that progressive moving patterns (from front to back with respect to the fly) elicit stronger responses than regressive moving ones (from back to front). Edges followed by darkness elicit a stronger response than those followed by light. A narrow, bright or dark stripe and a single edge evoke a similar response, whereas a broad stripe elicitis a stronger response than a single edge.