Scale, Soft Scale Insect, Plum Scale, European Fruit Lecanium, Brown Scale

This is my "Most Wanted" (villain) in the garden probably. A shiny, very dark maroon-brown type has infested my weeping flowering cherry the last couple years, and now my weeping Santa Rosa plum, (both are small specimens). This one is very honey-dewey- it looks like the trees are dripping wet. :( I noted the various scale types tend to mimic the host plants. I've seen a much larger, zebra-striped variety on my japanese maple trees (seedlings/not grafted) but not in profusion, thank goodness. My first experience with scale started on my abutilon plants. These scale are smaller, dull, near-black. I've found variety and placement of the plants makes a big difference with the abutilon- they tend to not get it as bad if they get enough exposure to sun/air circulation etc. There is a symbiosis... read more with ants so often I'll see ants too, sometimes that's what draws my attention. I believe I'm observing a predatory beetle, one I've seen forever around but do not know what it is- they are elongate, charcoal-color winged(shell), with orange-red head/thorax/ab. They appear in profusion early spring and just this year I began to suspect they are predatory (beneficial?). I would love to learn more. Unfortunately, even if they are they aren't making a dent-- the scale infestation on my prunus is very serious this year and I am going to have to do something. My reading suggests once they hatch they are harder to treat. Suggestions welcome! I have tried manually scraping but it's a disgusting, tedious job!

This is a common pest on a number of plants and trees especially stone fruits.
A useful guide to the control of this species is provided here:
http://www.rhs.org.uk/advice/profiles0201/brown_scale.asp