Be aware of the sensing capability of your camera. Place your camera well with in that range. Too close or too far will result in missed pictures. In most cases 15 to 20 feet to the target area in the summer is about right. During the colder weather some cameras will sense out to 100 feet. This can be a problem when cold and darkness allows the camera to trigger outside the range of the flash.
Originally posted by pazcat
How about a bug of some kind crawling across the lens.
That's what it looks like to me.