Most North American Myrmica are primarily scavenger species, found in cooler environments or steppe/mountainous like environments. In California these will either be the more arid species that occupy the hilly grassland like areas of southeast California or occupying the more damp mountainous north and eastern California. If I'm not mistaken, since not very familiar with many Myrmica species let alone Californian ones.
M. incompleta is an oddball that has a very wide distribution and seems to predominantly occupy wet foresty areas, and forms large polygynous and polydomous colonies. In California they are probably restricted to the north east or east.
Most North American Myrmica species are rather modest in terms of colony size, typically possessing one to a few queens and a couple of hundred workers, Myrmica in general are rather non-aggressive species and neither do they grow fast (especially when rearing the first workers, takes a couple of months to get one or two).
My experiences with M. incompleta are finicky at best. They seem to require very high relative humidity, heating and a diet rich in carbohydrates. Not sure about elsewhere but the queens here come in two forms, and they must be provided adequate space or they tend to kill each other (the larger form requires much more space than the other). M. rubra are also in my area and M. incompleta are definitely not as polygynous. They are equally aggressive though towards prey it seems but not as quick to sting. They are also noticeably polymorphic so that's cool.
Really compared to all other Myrmica, M. rubra is an exception.
Dermy resides in Northern Saskatchewan, his Myrmica are most likely M. nearctica or M. alaskensis, both of which are mostly restricted to Canada. They comprise most of the ant fauna where he lives.