@Kho Well yeah, but you can imagine that suddenly having yet another giant herbivore would cause a lot of problems, especially an exoskeletal one which would have to no clear predator for a long long while. I know the main damage would be on the Deepwoods but those things irradiate, species flee, tensions rise. Furthermore, as you originally stated, formicas did bring change to the flora. Either way, its not a mass extinction like the others, but I couldn't see it not causing a deep strike on the balance of things.