Im not sure but I think it may be a Dorylus genus? These huge ants would march around the poolside all day in their hundreds! Occasionally if they found something too large to carry, the smaller ones (to the right) would stand on their hind legs and wave their front legs in the air (no doubt emitting some inaudible sound to my ears) and within a minute or so, a huge ant (on the left) would appear and carve up the item in question!.. utterly fascinating afternoons :)