when should i start worrying?
Around here, I have dead out equipment sit until June with no problems.
And all summer if an ant colony moves in....... :-D
It takes the eggs a long time to hatch in cool weather. When daily average temps reach 50-60F it takes a month for the eggs to hatch. When it gets into the 70s for daily average the eggs will hatch in a week.
As long as we are having frosts at night, you don't have to worry. After May 1 in North Carolina and Virgina you should be on the lookout.
where do they come from? does there need to be hives around for them to breed or they live everywhere
I was shocked to find wax moths in my empty combs in the garage, which is unheated through a WI winter. AND my empty hives loaded with mice, but that's another issue.