Thank you all for your replies and advice!
I’ll try some wet qtips with the next stuck one.
But of course i’d prefer them to not get stuck in the first place.
I tend to cut off the pieces of branches or leaves on which the caterpillars sit to moult and put all the moulting ones in a separated box so they are left in peace, but maybe that’s too much manipulation?
I’m keeping the caterpillars in plastic boxes (with air holes), so i’m a bit scared spraying will cause mold although i do spray the leaves occasionally.
I do have netting cages too but it dries out the leaves so fast. Also the plastic boxes are stackable thus take up less space (my space is quite limited).
It’s just that i find the plastic boxes more practical to keep caterpillars in instead of the netting cages.
But, indeed, because they are kept in plastic boxes i make sure to clean them out daily (set aside all branches with caterpillars on them, remove old and dried out leaves, frass and replace the paper towels) so it is very likely that i handle them too much.
The air in the room might be too dry though, but i figured inside the boxes should be more humid as the paper towels at the bottom of the boxes are always slightly damp
Oh yes, those black spots, i noticed those last year too, and I just saw a tiny spot on one of the caterpillars today too.
Could it be mold?
When one starts the shedding and ends up being stuck, how much time is there before they start to suffocate?