Cleaning out the bin with a strong-smelling cleaning product might also discourage flies, or you could try limiting the amount of high-protein food (meat, cheese etc) that you discard, as they will prefer to lay on these types of foods. But also consider that the maggots are playing their part in the composting process and aren't doing you any harm. Granted they will eventually develop into flies, which are more of a problem, but this shouldn't happen until after the waste has been taken to the processing plant.

I haven't had a maggot problem yet, but had thought about it. It occurred to me that an occasional spray with fly-killer would inhibit infestation.

Maggots are because a fly has laid eggs somewhere on the caddy or bag, a good shake of the bag will get them off, rinse the caddy with boiling water and disinfectant which kills them and turns them into a soup you can pour away down a street drain, using a fly spray will help keep the flies away,

I am seriously paranoid about throwing away my food waste nowadays for fear that the fly eggs would hatch and there would be maggots jumping out of the bin. But that hasn't happened (yet), though I wish the service would be more frequent. Back in my country, the service provided pick up every two days, and although there were some off days for whatever reason (and maggots would eventually be popping out of the bin by then), there is comfort they won't be there too long.

Thank you for the tips.

I could not understand how flies were getting into a closed caddy in the kitchen but last night I saw eggs on the cornstarch bag under the rim but on the outside. So it would seem that when the bag is full we pop it in the outside bin (with eggs) and the worms develop out there. This is really disgusting there is no way we are keeping the caddy inside anymore. Thanks for comments and suggestions.

Hi, bit belated, but this may be a problem again soon! There is a product called Diatomaceous Earth which is a natural insecticide. It is a type of earth with very sharp particles, like pumice, which can be used to deter insects from settling to lay eggs but does not put any nasty chemicals into the resulting compost. You can buy varying quantities all over the internet, and there's a wikipedia article explaining how it works, if you want to know more. It is recommended for use in composting toilets, so regularly emptied food waste should be a doddle!