I placed them in a 6qt steralite container filled about 4 inches with a 50%/50% (by weight) sand and loess mixture (each sifted through #14 screen). I wet the substrate until it turned from a fine powder to a solid, placed the 2.1 beetles in the container and fed them heavily. 3 weeks after introduction I saw eggs and oviposition holes and then 12-14 days later the burrows opened up. Sexing them is fairly straight forward with an examination of the final abdominal sternite. I placed two fair sized rocks in the container because there was a few sources that mentioned A. baroni and other Amblycheila sp. were found as larvae around boulders. Interestingly enough the oviposition and the burrows are all formed next to or very near the rocks.
They are kept at room temperature 65-80 degrees F (low/high). I feed them at least 4 times a week with wild caught moths, flies, and 1/4 inch crickets from the local pet store.
I produced 45 larvae from the single female and most of them ar enow in second instar. If you would like anymore information feel free to ask.

Humidity is maintained by a heavy misting 2 times a week. I have no specific numbers on humidity % but I imagine it is somewhere in the 50-70% range. The I allow the container to dry out a few times a year just because this is a desert species and that is what nature does to them.

Thanks for all the information! May I ask what are you feeding the larva currently? And do you mind if I put a link to this on Beetleforum.net? This a very cool discovery, and I do not belive anyone else has been able to get these to lay eggs in captivity.
PS: This is probably a stupid question but where do you get loess?