You posted about your praying mantis quite some time ago. I assume those egg sacs are still waiting to hatch.

What fun! Be sure to spray a little water in there for her occasionally.

We often keep these as pets at our school too. When they hatch, there will be a lot of babies. Cannot give you an exact number. They need places to hide and things to eat or they will eat each other. We usually let them go as soon as they hatch. We always see grown ones around the school and assume they are the babies we released. We catch a few, and the process starts all over again!