Insect and Spider Identification: CLOSED: I thought I had a Mealy Bug on my Cactus???, 5 by bluemerle

bluemerle wrote:
Something caught my eye on one of Cactus, so I went and got my laptop &
Digital Microscope. Even the folks on my Cactus Forum are stumped.

First this little spots appeared, then got a little bigger, then this rather huge black head emerged from one of the fuzzy areas cactus have around their spines. The wooly area was larger than the rest, that's what got my attention in the first place.

This whole event took place in a matter of 15 minutes before I sprayed it with
soapy water,(at the advice of the forum), and a tiny black dot fell out and the big black head disappeared.
A girl from the UK said it couldn't be a Mealybug, and presented a photo of a real white one out in the open. Still had no clue as to what the big black head was.

Got any ideas yourself? I'm dying or curiosity and worry. The last one is the "real" mealybug It's real tiny, can you see it?
I'll try to put them in sequence. I have several more of the big black head stage, but they're so similar.
Thanks, Diane