The boulders are set up on a park....not sure about the Asian beetle thing as there were ladybug nymphs also in there?

are firmly established here, just like the European Sevenspotted one. So you'll see larvae and pupae. I think the term nymph is reserved for the orders with incomplete methamorphosis like grasshoppers and bugs.

lol...I was trying to thnk of the correct term for the young...I had to ask my son and we both just decided 'nymph' would work. So does the young of the asian ones look like the ones of the ladybird beetles here in the states?

The larvae are similar to other ladybug larvae, but can be distinguished by their forked spines:

I know some aphids are subterranean and will feed on the roots of plants. I've witnessed similar insects, I believe to be aphids or some other dew producing bug in ant colonies inhabiting rotten wood. Perhaps these aphids are feeding on some fungus growing on the rock?

These boulders have been freshly set out in this park...they've only been there at most 2 months. No lichen or fungi or anything else growing on them? Also, this was the only spot on ANY of the boulders where these were at? There was a statue near-by that had a very tiny amount of the aphids on it...but NOTHING like this mass.