Curse on Mealie Bugs please!

[Kath]

I had an infestation of mealie bugs sometime ago, and a few days ago, I saw more of these animals of a phal that had been clear of any bugs up until then. Can someone tell me where they come from, and where do they hide, in order to pop out from nowhere one day, when I least expect it! In the medium? In corners? I found a few under the leaves too.