Yes, because the adults climb alot but rarely fly unless really distrubed. What happens is the nymphs stay in the substrate, the adults stay in/on top of the substrate (burrowing in somewhat) and adults can/do climb all around in the cage (there is a screen top). The Vaseline is to keep them from climbing up to the screen top and wiggling out near a thin opening. They will only fly out if there is no top on the enclosure and they are pretty crowded. I regularly take the screen off to water or feed them, or to scoop some out for someone and have zero fly out. Really they are excellent fliers but not inclined to fly unless they really need to. Gyna are also excellent fliers but even less inclined to fly than P.nivea. I once spilled a whole bin of Gyna lurida on the floor and only after much chasing around did a couple fly up to a window where I nabbed them.In your 5th photo here, is that P. nivea? So you still put petroleum jelly around the top even though they can fly? Is this the same way you would set up for Gyna?