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Why do flies suddenly appear every time you open a beer?

It is universally known that when a beer is opened outside it attracts flies.  Scientists have now figured out how and why fruit flies magically appear whenever a can of beer of bottle of wine is opened.  The research team based at the California Institute of Technology have published their results in the journal Nature – findings which have overturned earlier scientific consensus. Their study spanned thousands of experiments over a 6 year period and contrary to thought, Fruit Flies are actually attracted to Carbon Dioxide and not repelled.

The study was led by Dr Floris van Breugel and finally concluded the paradox surrounding Fruit Flies response to Carbon Dioxide that has baffled scientists for years. Professor Michael Dickinson, whose laboratory was used to carry out the research, said “The scientific literature about insects broadly shows that CO2 is a universal attractant, but a long series of papers claimed that fruit flies are averse to CO2. They’re basically the only insect for which that was reported.” The consensus baffled scientists as fruit flies eat yeast, a single-celled fungi that produces CO2 as it ferments sugars. “Drosophila melanogaster, the standard laboratory fruit fly, evolved to eat the yeast that lives in fermenting fruit,” Professor Dickinson said. “It is a yeast specialist, and not just a yeast specialist but basically a brewing yeast specialist. The flies co-evolved with humans to live off of what we use to make beer and wine.”

Dr Van Breugel was inspired to carry put the experiment when thinking about the fermentation process during the course of a home brewing project. At this point in the experiment, in the Dickinson Lab’s wind tunnel involved mosquitoes or flies buzzing around or landing on a platform from which plumes of CO2 were released while cameras tracked their movements. “I thought, ‘Why don’t I put some flies in the same arena and see what they do?'” Dr van Breugel said. “After I ran the experiment, I found that the flies had actually crawled through the tube where the CO2 was being emitted into the wind tunnel-they just kept crawling! So that confirmed that they are, indeed, attracted to CO2 and that I should really investigate that more closely.”

During the course of the investigation, it was found that flies seek out Carbon Dioxide when they’re in their active state but avoid it when they’re sleepy or moving slowly. Dr van Breugel said the behaviour was probably the result of a balance between the reward of proximity to food sources and the risk of danger.