They're common for the trained eye, which this thread should help shed some light on.
Finding a nest in suburbia would be quite a feat.
Nigrocincta are all over the place, where I live anyways.
Probably not the best candidate for a formicarium though, They are jumpers and their speed and agility is often overlooked.
Plus they are the daytime warriors so you will always have them running (or hopping) around looking for trouble.
Brevinoda nests are scattered among them in fewer numbers.
I've seen Chrysogaster in my yard but they are elusive and quite small. Also agile and fast.
Sometimes I will see one of these little guys on my wheelie bin, as I approach it spots me, turns and plants it for the edge at which point it just leaps off like a base jumper, I always look but never see a parachute open.
I have walked trails and counted 15 nigrocincta nests along a 1 kilometer stretch.Some within metres of each other.
Then would walk another few kilometers and not see a single one.
Further south there are larger black species like Pyroformis but I personally haven't seen them up here.
This Brevinoda nest was hard to find being nothing more than a small hump near a sapling.
I knocked the top off and was surprised to find a sizeable number of sizeable ants.
It looked like it might rain later that day so I put a piece of wood over it and returned the next day to see they had sealed up around the timber.