Trying to swat a fly can be among the most frustrating household activities. Now scientists know why it is so hard.

The fly's escape secret: It jumps rather than just trying to fly.

In a new study, researchers were interested in how a fly's brain executes the life-saving move. Gwyneth Card of the California Institute of Technology dropped black disks from different angles, each on course to squash a fly. She videotaped the scenes.

The video revealed that flies jump directly away from the incoming objects, using both their legs and wings. The results suggest the brain initiates a take-off sequence that involves a "giant fiber pathway" of nerve impulses to the wings and legs.

"This kind of low-power decision-making could be of interest to those building autonomously navigating robots," Card said.

The results will be presented Wednesday at the Society for Experimental Biology Annual Main Meeting in Barcelona, Spain.

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