Deid Bugs on your car for weeks? Pure laziness!!!
Whatever you do, you should maybe soak them for a while to soften up their poor smashed wee bodies, rather than trying to scrape them off 'in one go'.
Not really sure what to do, you see I always wash them off straight away, because I'm a good boy who loves his car and not a workshy layabout who indulges herself with tea and crisps...