AR15 with a loudener. They're animals, loud gunshots will scare them off, even a t rex wouldnt fuck with that.

Also giant bugs like in the OP were a Carboniferous thing and if you were in the carboniferous you'd more have to worry about the crazy high humidity/heat/oxygen levels making the entre world into a petri dish. Weird prehistoric illnesses are something to worry about in the Cretaceous, but they're guaranteed in the Carboniferous. Though in the Carboniferous I'd still carry buckshot or something for the bugs, lots of them would absolutely fuck with a human