Phyllis, I'm a huge fan of Spectracide fire ant bait. It takes a few days to really get into the mound, but for me it's always been more effective than Amdro.
Cheryl, you may have had 'big head' ants. Seriously, that's what they're called! The ants are all different sizes, and the only identifying is if one of the workers makes an appearance - and it will have a BIG head!
