What is this, a wasp or a bee?

I am curious, it is the only really skinny "bee" I have seen on our marigolds which I bought 3 years ago on a visit to Ballenberg, the Switzerland open air museum of all the cantons.. They are so prolific probably as they are old genetic stock, that we have tons of bees all the time the sun is out. The marigolds do have to be pulled up by the handfuls as they seed so effectively they take all the sustenance from the vegetable plot. I alway let them go to seed though, they are so beautiful.
Rain and storms have chased the bees away now.