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Spitting Flies

October 13, 2005

Flies seem to like to eat the same things we do, but they have a very different method.


Dispelling a myth about flies. I’m Bob Hirshon and this is Science Update.

Friends of my daughter Carolyn grossed her out by repeating the urban legend that every time a fly lands, it regurgitates. She called our Why Is It line to find out if it’s true.

Medical entomologist Jonathan Day of the University of Florida says there’s some truth to the rumor. Except flies don’t regurgitate every time they land—only when they land on food they plan to eat.

JONATHAN DAY (University of Florida):
They regurgitate an enzyme onto the food. That enzyme starts to predigest whatever they’re feeding on—whether it’s a baloney sandwich or a piece of garbage around the garbage pail. They then lap up whatever is predigested and that’s how they ingest their food.

If a science question is bugging you, call us at 1-800-why-isit. If we use it on the air, you’ll get a Science Update mug.

I’m Bob Hirshon, for AAAS, the science society.