From OSU EU:
After mantids have completed their early stages, they may be fed insects larger than aphids and vinegar flies such as mosquitoes, flies, and roaches. Mature Chinese mantids readily attack, kill, and devour large crickets and grasshoppers. Some people like to watch the capture of this prey. Others like to collect adult mantids (especially females full of eggs), then place them in a large glass container (empty fish aquarium) and watch egg masses being glued to an inserted tree branch. After egg laying, mantid death usually occurs a few weeks later.
Egg masses, collected in September or October and brought into the warm classroom, have been known to hatch in early December of the same year. Then, large numbers of very tiny mantids will suddenly appear and, if not furnished fresh, live food, they will eat each other until only one or a few mantids are left.
Well, that explains why I've only been able to find two praying mantids in my garden. I was looking for life cycle information - the sad news: one season.