I've been seeing a few of these on my nandina plant out front. It doesn't look very bug-like. More like a miniature cross between a cigarette butt and a sweat sock. BugGuide has it here.
They must excrete honeydew similar to aphids, because ants were tending them.
The big white part is an egg sac. After disturbing the critter by plucking her, plant-stem and all, to get a better view, a few of the nymphs had emerged. They look like bugs.
They are not really affixed to the host plant, but just gripping onto it with their legs. I carefully removed one from the plant stem and posed it for a belly shot. You can see the skinny black legs. She was flailing like an overturned turtle. Not to worry, I put her back when I was done.