Ask A Scientist© Biology Archive

Question:  A grade 3 student working on a project on houseflies would 
like to know if flies sleep and if so where do they sleep?
Thanks for your help.
Shelley R Hasinoff

Answer:  I'm no expert on the pests, but I'd say they don't.  The problem,
though, is that sleep is not easy to define even in humans. We don't
understand what happens to our bodies when we sleep, how we sleep, or why
(although there are ideas about each of these). I think sleep is basically
defined as the unusual pattern in the electrical signals given off by the
brains of people who say (later) that they've been asleep.  Kind of a
circular definition, eh?  We can surmise that cats and dogs sleep because
they act like sleeping people --- lay down, close their eyes, don't
respond, snore and twitch when dreaming --- and they probably have similar
patterns in the electrical signals from their brains, though I don't know.
But with flies, now, they're so different that not seeing the same
behavior doesn't say much.  Still, I'd say they don't because the  most
convincing hypothesis I've heard about the reason for sleep is that it is
part of learning, and I've also heard that flies are capable of learning
anything at all.  That's an argument, but by no means an answer.  Sorry.
Christopher Grayce