There may be more biomass of ants and termites in rainforests than any other groups. When we were doing our research on animals of the rainforest we had a very difficult time finding information about the katydid especially the katydids that live in the tropical rainforest. I will tell you that for insects in general, not specifically katydids, the main difference between tropical and US species is their larger numbers. Actually, most rainforest species are quite specialized, and when their habitat is destroyed, they have little chance to adapt to a new one. That is why we are endangering so many species by cutting down rainforests.
Forest grows back very quickly in the tropics.
The problem is that it is secondary forest, not the original primary forest. The great biodiversity of Amazonia is threatened when large areas are deforested. When that happens we lose species, species we may never have identified, species that may have had vital genetic material, that might have been used for medicine. The forest that grows back will not have these species. That is a great question, but one that I cannot answer very well.