Kinda like ick, if it’s too warm for them to hibernate, they’ll hunt for food. If you have no reason to go down there, tape up door jams, windows, electrical outlets, etc, just need good masking tape to bar them from moving to other areas. Seal it off, up the heat, put out all your bombs and traps, and then check again a few months later. If it’s cold, they’ll wait it out, but if it’s warm, they don’t have such a good option, and will actively hunt for a host, burn up their energy reserves, and die. We moved into a house at one point that had them horribly. Sealed up the house, bombed it, then again once it was warm out, cleared out all the previous tenets stuff, bombed it again, then deep cleaned. That was a three month project of bombing, cleaning, and it seemed that by removing places for them to hide, heat, and bombs, we seriously reduced them. They did like you described, where you could see swarms of them climbing when we first went in. We were buying that place, so it was worth it, but then ended up loosing it because after all our work, the lady reneged on the deal and sold it out from under us.