California Velvety tree Ant, Liometopum occidentale live in decaying wood. They are common here is the dead trunks of trees or old logs. They really bite. They like to hang out in some of the Ceanothus and farm aphids. You bother a Ceanothus or coast Live oak and they show up, you leave. They also will nest in deck wood or old hose wood that is moist and decaying. Fix the house, don't blame the ants.
They also seem to be pollinators, surprise? On the sour cherry tree we have every flower has an ant in it. First the get a sip of nectar, then the check out the anthers, then the stigmas. They are very slow about it, one flower every few minutes, but they seem to be thorough.
California Velvety Tree Ant Liometopum occidentale