i have crickets in my basement not sure where they come from but when you put lights on you see 2 or 3 my wife driving me crazy about this they dont chirp, are brown and good size

We have a detached two room converted garage that is our guest building. When my dad and his fiance visited last fall, she complained that she was getting little bites on her arms and legs at night. My dad was unaffected. We figured it was the blanket she was using (as she had it wrapped around her as she read in a chair at night). Later, when we described this to my in-laws, they mentioned that they get the same thing every time they visit, but had just never told us! We have never been able to see anything, but don't really know what to look for. Could this be bed bugs? My wife did some reading, and thinks that it might be rat mites (the structure is post and pier, and the underside is easily accessible to critters). How should we go about identifying what is going on? We have not had a visitor since October, and the building has been unheated through an unusally cold (for Seattle) winter where we were below freezing for a week or so. I assume that with bed bugs, they would still be out there. If it is rat mites or something, there might be no sign of them, but they might come back if there is someone sleeping there. Thanks, ~john