There's a Dahlia on the left - you can just see the foliage/buds. Get yer big specs on, Jenny I'd remove all those flowers from the lily @Robert343, and any affected foliage too. The beetle larvae cover themselves with their poo, and it's easy to miss them. The beetles themselves are easy to spot, as pansyface indicates - bright red uppers. They can really devastate lilies. Once your dahlia has finished, it's worth removing the lily and replanting somewhere else, giving it an additional bit of liquid food to boost it. Keep an eye on it though next year, and if you see any adult beetles in the meantime, remove and squish them.
I said I could see dahlia foliage .