Yes, they are a good feeders. I always trying to get an ooths and get some mantids. So far I have been unsuccessful so I bought already hatched ones. For a big chameleon the small mantids will do nothing so you would need to feed them and get them bigger. It will take about two month to raise the mantids to a feeder worthy size. Luckily for me I have a baby chameleon that can enjoy a small mantis.
Some might say that you can find one in the wild, providing you are sure there were no pesticides in your area, and feed it to your chameleon. I am not to crazy about the idea, because I am not sure what pesticides are in my area and I do not want my cham get parasites.