When i was a kid i was told that these were fairies.
|Image from http://drawandshoot.files.wordpress.com/2012/08/thistle12.jpg|
I don't remember who told me but i believed they really were, and If you caught one you had to hold it carefully between cupped hands, make a wish and let it go.
I now know that they're thistle seeds.
It gives me a warm happy feeling inside thinking that someone might have caught it, wished on it and released it thinking it was a fairy like i used to.