I live in Indiana, in a house with a crawl space brimming with spiders. Two nights ago I noticed a mantid and nabbed it so my child could see one. After I showed it to her in the morning we were preparing to release it and it dawned on me that it could keep both the spiders and insects in check in the crawl space, so I released it there. Then I thought it might not be a bad idea to obtain some more mantids and put them in the crawl. Is this a bad idea? Will they eventually eat all of the other creatures and then cannibalize each other? Is an Indiana crawl space too cold in winter for a mantid to survive? If it's a good idea, how many mantids could a 30 x 60 x 4 space support? Several? Dozens?