I posted smugly on a recent thread where someone said that she had maggots in her bin, to say that we had never, ever in our lives had such a problem (and, more helpfully, to suggest that perhaps keeping the bins in the shade helped).
This week we had maggots for the first time ever!
So, I deduce that something we did this week must attract flies / maggots.
Two things were different this week - the main one being that we threw away a lot of uneaten food, mainly meat, and the second being that I think not all bags were securely knotted shut, but some were just pulled closed with drawstrings.
I therefore posit that one of these factors is key to maggots in bins.
Honestly, the bin this week was disgusting - normally our black bin is mainly non-recylable packaging and a few double wrapped bones, so not particularly smelly. This week it absolutely reeked, and of course had the lovely maggots.
I wondered whether many people do throw leftover meat into their dustbin and whether this is a major factor in encouraging flies? The meat appeared to rot into sort of decomposing fluids, which might be just what flies like.