I have found several of these creatures that sort of look like ants, but I don't believe they are.
I live in mid Michigan. I do have firewood in the room where they were found. The bugs don't seem to have very big mandibles compared to their size of 1cm. They have distinctive markings on their backs. Do you have any idea what they might be?
Sorry to take a few days to get back to you on this. I had to consult with a beetle expert colleague to make sure I was giving you the right information in this reply. Here's what he wrote: "They are cerambycid beetles - the first (0472 and 0473) are Cyrtophorus verrucosus, and the last (0474) is Euderces picipes. Yes, they are both ant-mimics (and a nice example of convergence as they are not particularly closely related to each other)." I would add that both of these beetles mature in dead wood, and no doubt were stimulated to emerge by the warmth inside your house.
We get quite a few inquiries about other critters that look more or less like ants. Some of these might be considered true ant mimics (other animals that look more definitely ant-like in appearance and outward behavior than other members of their respective taxonomic families), and others are not especially ant-like, but are perceived as such by folks having little experience with insects, generally. Here are a couple of relevant posts:
James C. Trager of the AntAsk Team