How do flies determine their escape paths? Scientists have answered this question by studying video footage of a wingless fly attempting to take to the air.

The question of whether a fly will move away from a threatening object coming towards it isn’t as silly as it sounds. To escape quickly, the fly has to transform sensory input (from a world that is predominantly much larger than it is) into an accurate motor response. The fact that it can do this says something about its nervous system.

By putting flies on tape and studying their behavior as a black disk descended towards them, scientists learned that the flies can respond to stimuli in 215 ms.

But was this response deliberate and accurate? This question is complicated by the fact that the fly has wings, and can adjust its direction once it’s already in the air. Perhaps the fly’s automatic response to any startling motion is to leap in a random, or semi-random, direction and then correct its motion once it’s airborne. To check this, scientists “surgically removed” the wings off flies and repeated the experiment.


The result: we see the fly hurl itself into the air and then go end-over-end like a poorly-thrown football, kicking its legs when it realizes it can’t fly.

So the flies without wings jumped in the same direction that the flies with wings flew. The fly’s response, therefore, was deliberate and quick—even though its follow-through was graceless.

[Source: Visually Mediated Motor Planning in the Escape Response of Drosophila]

Top Image: J Hoc