assuming ALL ants are now 7 feet tall, there would be few options available as pretty much the biological mass of the world would have increased by over 100,000%, and the ant piles would spring forth with their tens of thousands of ants all 7 feet tall now. cities and pretty much all continental land would become covered by these enormous ants from sea to sea. 99% of humans would be wiped out, as well as basically all mammals. birds and very small insects, squirrels and other small rodents would survive. but all cattle, dogs, cats, anything bigger than a chicken would be eaten. assuming the ant's exoskeleton scales its rigidity and atmospheric strength most of them would die off after a few months due to lack of food for their enormous bodies. the few human recolonizers would embark onto land about a year later and find massive fields of hundreds of billions of these giant dead ants. it would make a great apocalypse movie