Stuff that occurs to me

All of my 'how to' posts are tagged here. The most popular posts are about blocking and private accounts on Twitter, also the science communication jobs list. None of the science or medical information I might post to this blog should be taken as medical advice (I'm not medically trained).

Think of this blog as a sort of nursery for my half-baked ideas hence 'stuff that occurs to me'.

Contact: @JoBrodie Email: jo DOT brodie AT gmail DOT com

Science in London: The 2018/19 scientific society talks in London blog post

Friday, 30 January 2015

Why are these flies spinning on their backs?

Over Christmas and New Year I was in three different houses over a three week period: my own, my family's and a friend's. In my own and my family's house I witnessed a (single) fly flying past erratically, landing on its back and spinning at great speed. In my friend's house I heard my friend's husband wonder out loud what on earth a fly was doing - "is it spinning on its back?" I asked him - "yes".

What's this all about?

Are the flies trying to right themselves, recovering from a stunning injury, trying to free themselves from something, dying (seems awfully effortful, poor things), spinning for the hell of it or having some other neurological problem?

After a chat about it on Twitter it seems that it might be the effects of a pesticide that's causing a neurological effect. Perfectly plausible although none of us in the houses mentioned were using it, however flies do fly and they may have been sprayed elsewhere and arrived later at our respective houses in their agitated state.

A few months ago I had a wasps' nest sprayed with a white powder via a puffer. Shortly after the powder had been puffed on the nest the wasps left and swarmed outside it before dropping down and twitching (slowly) before dying.

This thing with the flies is very strange to see, I've never seen anything move that quickly under its own power - as you can see in the videos below it's quite a remarkable performance. This is just a selection of several videos on YouTube showing this phenomenon.


  1. I read that they get stuck on their back and they can't get back up so they eventually dye of starvation :( the big ones are called cluster flies which try to find buildings to hide and nest in when they sense temperatures start going downand it starts to get darker, you will probably start seeing them around August when mornings start to get darker. I just saw a cluster fly on my kitchen window spinning like mad on it's back and i tried to flick it up on it's feet with a spoon but it just kept going on it back :\ lol, perhaps they are dying and it's just their time to go? because flies go on their back when they are about to dye, we have been spyaying fly spray but that was the other day, this fly only just arrived so we haven't sprayed it... or done anything, but flies can get stuck on their back and dye of starvation too, but if they refuse to get up then it probably just means they are dying of natural causes.

  2. All day today my cat has acted lethargic and mopey. In my kitchen, I noticed first a bee spinning and then, minutes later, a fly spinning on its back. It concerns me that a pesticide has been used by my landlord without consulting me.

    1. Could ask your landlord... also do you have a problem with pests that might make your landlord put pesticide down? Depending on where you are in the world it could just be the heat and humidity too.


Comment policy: I enthusiastically welcome corrections and I entertain polite disagreement ;) Because of the nature of this blog it attracts a LOT - 5 a day at the moment - of spam comments (I write about spam practices,misleading marketing and unevidenced quackery) and so I'm more likely to post a pasted version of your comment, removing any hyperlinks.

Comments written in ALL CAPS LOCK will be deleted and I won't publish any pro-homeopathy comments, that ship has sailed I'm afraid (it's nonsense).