Someone, last year, (I believe it was Ruta) told me that this was evidence of "leaf miners." The columbine leaves have become miniature abstract paintings which, I admit, are captivating.
Disgusted as I am to be afflicted with the trails of this micro-pest, I'm also fascinated I can't seem to generate ill feelings toward an insect that manages to handcraft this oddly beautiful image.
I've noticed it seems to like tender young plants. Nastursiums--one of my beloved flowers, filled with childhood memories of sneaking a sip of nectar from the amputated tip--are riddled with the leftover trails of the leaf miners. The big green leaves bear the scars of the leaf miner's attention.
The new broccoli and cabbage starts also have evidence of visits by this bug. But the odd thing is that I have never seen one. I look for it on top, underneath...but none to be seen. I can only surmise that it's either very, very small or it only shows itself at night.
So much goes on that we don't see in this realm!
We watched a recent Netflix film entitled Microcosmos. All about insects. Here is a link to information about the film, done in 1996: http://www.imdb.com/title/tt0117040/ Throughout, there are no voice-overs. Only the sound of insects. And the photography is absolutely unbelievable! Treat yourself to a viewing if you have Netflix!
As for the invisible leaf miners...I'm rather enjoying their destructive natures, and they can continue to paint their message, so long as things don't get completely out of hand!