You wrote:
"Fighting Pests with the praying mantis appeals to me."

Mantids are interesting to see and to watch but do precious little when it comes to killing insects, pesky or not.

The reason: They sit and wait for lunch to walk by.

You cannot get the egg cases now since there are no Praying Mantids in them. Order in late winter for early spring delvery. While the Mantids pretty much wait for insects to come into reach they are very mobile in my yard and I see them walking all over and now the are quite big and fat. Just what they eat I have no idea, but my toads are also getting big and fat.

I have several that survived to adulthood but only like seven out of a few hundred. I say get 6 sacs if you don't mind being overrun by the itty bitty babies for a few days. They get eaten, or drowned in rain, or eat each other pretty quickly. The ones I still have are very large. BTW I didn't buy mine they were just born in my yard.

You can still buy egg cases this time of year since they are kept dormant with cold storage, but I agree with Jean that they are nice to have around, but do little to actually control a pest outbreak. They are also indiscriminant feeders, taking beneficials as well as pests.

Praying mantids are over-rated as beneficials. We do not recommend purchasing them.

They come on their own in my yard too...but I've still plenty of beneficials and they live happily together..I can say my aphid problem went from tons to almost zero in a few weeks that the babies appeared.
It's true tho that the will eat the beneficials, but as it's been mentioned only a few make it too adulthood and are WAY out-numbered.

Vera

Where can I purchase these egg cases?

Mellinger's, Peaceful Valley Garden Supply, and probably a number of others have them.