Utah State University Extension
The oystershell scale belongs to a group of insects called the armored scales. The adult insect is enclosed in a shell made up of its own shed skins and waxy secretions. Under this covering is a sac-like animal that is quite different in appearance from most insects. It has no legs, eyes, or antennae.
Karren, Jay B. and Roe, Alan H., "Oystershell Scale" (2012). All Current Publications. Paper 1359.