Flies. Maggots. Nasty.
Except they're not (well, sort of). Without maggots, we'd literally be neck-deep in crap. And there are many flies that are pollinators. Flies like this common greenbottle (Lucilia sericata) that was feeding off of the forget-me-nots (Myosotis sylvatica) whilst flitting about the garden today.
Not only does this fly do a good job of spreading the flower love, its offspring have a penchant for rotting flesh and have been successfully used for treating really manky wounds.
OK, so it's literally got shit breath (as have some humans I know) but perhaps you should think twice before going to swat one in future (if you're the sort of Neandethal who does that sort of thing). A world without flies and maggots would be a far more disgusting place.