Beetles Eat Wood
Is it possible these beetles are eating through this wood by my back sliding glass door? If so what should I do? Or is this from something else? There were several of these beetles alive and dead near this area. See attached photos.
I can confirm that the beetle in your first image is a powderpost beetle and that the larvae of this beetle do indeed "feed on wood and, given enough time, can reduce it to a mass of fine powder." Wikipedia
It is likely that you are going to have to replace the wood where there is an active infestation (as determined by the fine sawdust under the wood pieces). Re-infestation can be prevented by treating any raw wood with a paint or varnish coating.
I do hope this helps!