Chrysalis

From Alien Species

A very large (around the same size as a Praetorian) Xenomorph with a greyish-green exoskeleton and a hard, tan carapace on its head, back, and forearms. It sometimes moves/attacks by rolling itself along the ground in a ball. It gets its name from the chrysalis that it is seen gestating in when it first appears. The Chrysalis's head can actually extend a short distance from underneath the carapace over its head when biting its prey, in addition to the extension of the inner mouth. More Chrysalis are also seen defending the Queen during the final battle. These have a reddish or blue coloring.

A variation of the Chrysalis appears in the second level of the Konami "Aliens" arcade game, but it looks considerably different and has a different attack pattern.