Hi Cora and thanks for your picture of the mantis egg case. It would help to know where you found the case or if you bought it, and how long it has been there. There are no native mantids in the Willamette Valley, but definitely some east of the mountains. They are considered predators of all kinds of other insects, but if you want to take the egg case and raise them in captivity, just feed them some fruit flies and when bigger grasshoppers and maybe we can identify them.