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Well, this morning I went to take out the cloth I had across the top of the butterfly terrarium. I figured by now they would be large enough not to get through the little vent holes. Well, surprise!
Overnight a lot of them started to make chrysalis! They have attached themselves to the cloth with the little silk button.
The ones starting to do this look like a hook shape.
You can see what these caterpillars looked like after they turned into Painted Lady butterflies here.