Praying Mantis Egg Casing on a Mesquite Limb in Sabino Canyon — Image by kenne
This Styrofoam-like mass was created by a female praying mantis to protect a mass of 200-400 eggs. This egg case is called an ootheca. Females typically lay their eggs in the fall. Tiny mantid nymphs will hatch from their eggs while still inside the egg case and make their way out of the ootheca approximately three months later.
— kenne
We used to get a lot of these when we had a pet Praying Mantis. We then would put the casings outdoors. 🙂
Having recently been informed about mantis mating shenanigans, I say: good luck to the newborn boys!