There we were minding our own business at a family picnic when fruit flies descended on our lunch like an invading army. Alas, our swatting resulted in very few casualties. I am sure they snuck off with bites of this and that, although we may have found a few victims in the lemonade.
So, why is it so difficult to swat fruit flies? I had a sudden desire to know how to defeat these sneaky snackers and did some digging. In the process, I came across an article published in the Journal of Neurophysiology in 2009 that described how Drosophila melanogaster make their getaway.
To escape, an animal needs to quickly gather sensory information about approaching dangers (vision, smell, movements of the air) and process that information using sensory centers in the brain that communicate with muscle control centers to stimulate muscle contraction – thus enabling their escape. For example, approaching objects create a shadow and disturb the air thus triggering an escape response. Similarly, just turning off the light creates an escape response in fruit flies. Interestingly, different neurons are activated by turning the lights off as compared to creating air disturbances by looming (like my hand attempting to swat them). In response to a looming threat, the flies raise their wings before jumping. Combined, these two pathways provide formidable protection from human hands and other approaching objects.
Cover your fruit everyone. No picnic is safe.
H Fotowat, A Fayyazuddin, HJ Bellen, F Gabbiani. A Novel Neuronal Pathway for Visually Guided Escape in Drosophila melanogaster. Journal of Neurophysiology. 102(2): 875-885, 2009.