I spent lazy August days hiding in the shade of pond-side hardwoods, tossing all sorts of creepy crawlers into the water. But what I saw was that no living insect on the water would survive. As long as it was alive and moving it would always disappear in a swirl, although a matter of minutes might first have elapsed. Bluegill always subject floating food forms to a close examination, but the duration and intensity of that inspection depends upon four factors. No artificial will pass a lengthy inspection, no matter how well tied, and top-water success demands that we find ways to moderate this reality.
Size is certainly the most crucial of the four factors.
After a great deal of observation, there is no question that these fish subject small insects to much less scrutiny. I regret that I didn't time such examinations with a stop watch and construct charts demonstrating the correlation between duration and size that I know to exist. Maybe I'll get around to it next season . . . Movement is only slightly less important than size. Inspection is longer and more intense if the insect is either completely dead or extremely active.