I have been silently enjoying and benefiting from the forums for a while, time to post.
I've been keeping darklings for a couple of years. I currently have them in a communal set up (I know, but it looks cool!) Lets see, I currently have a bunch of Asbolus verrucosus, Cryptoglossa variolosa, Asbolus laevis, Phloeodes diabolicus, Eleodes suturalis. A pair of Eleodes osculans, a single Eleodes spinipes, and a handful from a few different species I'm not sure of.
They're in a tank with eight velvet ants of four species. As well as three cactus longhorn beetles. I started with six of the longhorns, unfortunately velvet ants seem to be fascinated by something they sense on the heads of the longhorn beetles. The three beetles I lost were all large females, they have the tendency to flick velvet ants off of their heads with antennae which the smaller females and males don't seem to do. Needless to say it wasn't appreciated.
Also have a couple of dung beetle tanks Phanaeus vindex and a Canthon sp. Have had success breeding the Canthon, nothing from Phanaeus yet.
Ahh and a couple of Cotinis mutabilis.
Cheers!