The same thing happens to me all the time. I take a shot and really don't like it and then a few weeks later I really like it. I think I finally figured out why... its because on the day I took it, it doesn't look at all like how I had imagined it in my mind's eye when I took it so I am disappointed. A couple of weeks later I am just seeing it as a photo without the memory of what I wanted it to be and so I can judge it on its own merits.
By the way, I like this photo of yours very much... You do a great job with these insect silhouettes... they take on gargantuan proportions.
