Cayuga, sometimes there will be eggs left even after you have killed off all the mealybugs you can see. You need to treat the plant twice or 3 times over the course of a couple of weeks before you can be sure of killing off all the generations.
I've had good success with an insecticide containing Spinosad, which (thankfully) is also an organic control. My orchids sometimes develop mealybug infestations when they're getting ready to bloom, and it's important to 'flow' the insecticide down into the leaf axils (where they join the stem) to get all the young bugs hiding there.
