I have been a bit busy recently; too busy to give this website the attention it warrants. In fact, I said to myself yesterday, I have been running around like a blue-arsed fly.

I stopped to think: why a blue-arsed fly? Is there such a creature? There are many things called red-headed, red-tailed, red-legged, red-breasted and so on, but none I have heard of named for the colour of their posterior.

In any case, why would one "run around" like a fly of any sort?

Can anyone shed some light on the matter?

  • Well, one cannot possibly fly. You run around because you are as busy as the blue-arsed fly. I'd go with @Jeff's answer.
    – Jimi Oke
    Dec 22, 2010 at 7:52
  • Surely this is an Australian expression, btw ??
    – Fattie
    Mar 23, 2015 at 8:23
  • "running around" of course, obviously, can mean "going around" "doing things", with utterly no connection to physically running (ie, running in the sense of the 100m olympic sport). It's absolutely commonplace to talk of "running around town in your car" for example. Obviously, the significant part of the question is the "blue-arsed fly" part.
    – Fattie
    Apr 7, 2016 at 14:21

6 Answers 6


A quick look at Yahoo Answers gave me this:

Certainly the fly in question is a bluebottle, but I think I'm right in saying that the expression originally was "buzzing around like a blue-arsed fly", which makes a lot more sense. One more normally tends to "run around like a headless chicken".

Sounds plausible...


Seems like a bit of a mixed metaphor. Run around is a common expression meaning to be busy, frantic, or otherwise getting the runaround. But to emphasize how much one is running around, we turn to metaphor. The fly in question is apparently a blue bottle fly, which buzzes around rather frantically, like someone who is running around busily doing errands.


If you watch a bluebottle, the fly in question, they buzz around in a generally hectic and irritating fashion without - as far as one can tell - getting much done.

If one is running around like a blue-arsed fly you are not running around in the same way the fly would run around, but you are running around in the way the fly will fly around- hectic, hurried, noisy, maybe a little annoying and typically not - as far as one can tell - getting much done.


When I was young we often referred to the bluebottle as a 'blue house fly'. It is most likely that the modern expression of 'blue-arsed fly' is corrupted from this expression. Such mutations or derivations of expressions based on how they sound is, of course, not uncommon. The problem is producing evidence to back this up from an era before everyone told you what they just had for breakfast through social media!

  • I wonder why this was downvoted? It sounds credible to me. There are parts of northern England where 'house' is pronounced more like 'arse'.
    – Mynamite
    Jan 26, 2013 at 17:18
  • More likely the other way round - I suspect the fly was originally known as the blue-arse fly, and via rhyming slang* was euphemised to blue-bottle. There's also a green-bottle, btw. *bottle and glass
    – peterG
    Jan 19, 2014 at 2:19

Comes from the times of slave labour in sugar cane/cotton plantations where the masters would make their slaves bend their backs in the fields with their rears (black/blue arses) in the air. "We shall make them work like blue arssed flies"!

This was told to my father by his father who was born in 1856.


I think it is because you are trying to catch fish. It may sound a bit stupid but quite often when you go down to the river to catch fish with a rod and line you can tie an immitation fly to the hook instead of using a bait. They call it fly fishing and all the flys come in all sorts of bright and exotic colours including blue.

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