Catching Bats and Ideas

I took this photo last night at sunset, trying to capture the bats flying just below the branches, black flashes silhouetted against the lake. There were about a dozen of them zinging back and forth.  I took six or seven photos in quick succession, sure that I had caught them, but I don't see them now.

When I am in book-writing mode, I often try to capture quick flashes that flit through my mind–a scene, an image, a snip of dialogue–but sometimes they elude me, like the bats. I know they were there, but where have they gone?