During some colder days I brought some twigs form the nearby woods, and after placing one in the enclosure, some ants sprung out of it!
I use a lot of twigs, and I have some really cool ones - they don't lose leaves during winter, and are perfect for my Gongylus, because they really seem to imitate their natural habitat, and abundant and strong leaves provide a lot of perching places and so on.
Live plants are great for mantids that like humid conditions, the only problem is that some plants grow a bit too fast, and you have to remove excess branches, or else there might be a space issue, where your mantids won't be able to find good and safe places to molt.