So Colt really did turn to humans for help. Motives are a bit dull considering what he's been doing until now.
What does it change if there's a chain of command or not when you're similarly killing everyone/everything around?
The only difference would be speed/level of mass murder.
I do not think Colt cares for ecosystem balance...

It might suggest though, that hormonal control was a key factor. You could always think that when the Queen's reproductive organs were destroyed, she also lost hormonal control over her ant army, freeing them... even Colt who can now let some of his human parts take over.