Thanks guys.
I agree with Afish that trout can become jaded to floating ant patterns, esp those in typical sizes #18-14. This is particularly, pronounced in reg waters that are heavily pressured like Yellow Br or Fishermen's Paradise. I first noticed this back in the 1980s when the McMurray Ant was so popular. (Since then, with the popularity of closed cell foam McMurray ant bodies have faded and I've met some FFers with a decade or less experience who have never seen one). Anyway, so many folks were throwing McM ants that the fish just seemed to get jaded. They'd eat 'em with gusto in May/June but by late July you had to switch to some other terrestrial or downsize your ants to very small.
Personally, I love foam and use it on virtually all my surface terrestrials now. However, in my experience, you get some diminishing returns with foam flies smaller than #20 and I often found that very small foam ants didn't float well for me and still maintain a slender profile. The photo below shows some of my ants. The foam fella on the lower right is a size #18 (still dwarfs the #24 red ant) and is my go-to ant pattern. The big one on the left is a wet ant. I like a glass bead for the head to give wet ants some weight to sink. This glass bead wet ant is a #14.
Of some note - notice the foam and wet ant are mixed brown and black. While all black ant flies are deadly, and most of my black micro ants are all black....if you take the time to look at many of the large carpenter ants common here in central PA, they are in fact different colors with black heads and thorax but brown abdomens. Don't know if trout really care about this distinction but I usually tie my bigger ants this way.