What are they in?

Are they pantry pests? If so, put a little mesh bag (I use panty hose) of dry bay leaves in cabinets and tape to the top of flour containers, etc. Since I have done this, I haven't seen a single beetle.

No. They are just pock marks on a floor joist in the crawlspace, which is a tell-tale sigh of powder post bettles. Haven't encountered any in the home. I've done research and it turns out these beetles lay their eggs in the wood where the larvae can sustain themselves on the wood for several years before boring out of the wood.

The beetles will target lumber yards and sometimes lay eggs in fresh milled wood. The eggs are deposited, the material is then delivered to the contractor and thus the job site where it is installed and things may look fine during construction and shortly thereafter but in a year or two an inspection may discover their presence thru the damaged wood. Boracare is recommended to spray on new joists, studs for remodeling as it prevents infestations.

I have powder post beetles in my barn. They leave behind a powdery sawdust material. They burrow in untreated wood and lay their eggs. My barn is very close to the neighbor's barn and I have moisture problems in that one wall because of it. You can try fumigating, but they'll come back.If its just a few pieces of wood, get rid of that wood, sweep up all the powdery residue. Get completely dry, chemically treated wood.Vanishing the wood is good. Prevents crevices for the bugs to burrow in.