Mealy bugs are sucking insects like aphids that secrete a powdery wax layer to protect themselves. They are further protected from predators by ants that are attracted to a honeydew secretion. Note the upward facing anus for the ants' use. (This brings a whole new aspect to the saying "kiss my __" enough said).
When the wax is cleaned off mealy bugs are surprisingly colourful with dinky little legs. Excess honeydew secretions that drip down the branch are used by moulds to create a black sooty stain that can be seen on the stem and the ground below the shrub in the image below.
I have met some humans like that but they eat, and also live much longer.
These oval sucking insects are similar to mealybugs, but are hermaphrodites that produce hundreds of eggs in white cottony looking ovisacs that extrude in different shapes from their body. The young are quite mobile but adults can attach themselves to the plant using waxy secretions.
I couldn’t dislodge the one that looks like a tubular alien (luckily it wasn’t as I escaped from being disintegrated, ingested or colonised).
May you truly appreciate these small wonders of nature as you spray or scrape them off your favourite plants.