I got some of the net/mesh I use for felting and I put it right under the pot then lifted it up so it goes round the base of the greenhouse thingy then I taped it on. I think I have an escape/insect/wasp proof prison now.
The huge one managed to creep off and make a chrysalis somewhere before I made the prison and I can't find him. However I still have three simply gigantic ones and I rescued one teeny one from the outside swan plants, so there are 4 in Monarch Prison.
I've been watching them on and off all day and it's fascinating. You will never guess what I got a photo of one doing...
No, that is not his face, and Yes, he is doing a poo!
munch, munch, munch!
I also took a wee video - steady cam it's not, but it gives an idea of how they eat and move around. You can see the tiny one on the left side on the same leaf as one of the big ones, it shows how much they grow.