In the fall mantis eggs, Ootheca are found throughout the USA. They are a little hard to find but once the leaves have all fallen and branches are bare they are visible. Some days I can find up to 100 ooths! 
Im getting older now and asking if anyone collects mantis ooths to contact me and I’ll buy them. I supply them to greenhouse growers and people who want natural pest control. They eat all the nasty pests as they are insectivorous and devour insects including Lantern flies, stink bugs, mites, aphids, caterpillars, and other insect pests. Some are considered invasive and people collect and destroy the eggs, however for greenhouse growers and the like they are a wonderful natural way to protect their plants.

if you collect mantis eggs, don’t destroy them, I’ll pay you to send them to me. 

Contact me Craig B