Coleoptera: Cerambycidae. This is the flat oak borer, a type of longhorned beetle. Here is some info from Linsley (1962): "The eggs are laid in crevices in exposed wood and the larvae excavate meandering galleries in dry heartwood, packing them tightly with fine granular frass. The pupal cell is formed near the surface by enlarging the mine. The life cycle, normally requiring a year, may be extended under dry conditions. According to Craighead (1950), stored lumber is frequently found infested, the larvae continuing to feed until the wood is thoroughly riddled. Knull (1946) reports occasional damage to log cabins." The exit holes made by emerging adults are small and oval-shaped.
This species of longhorned beetle isn't usually considered to be a major pest like its relative, the old house borer. It only attacks hardwoods (no softwoods like pine), with oak and hickory preferred. Since it can reinfest seasoned wood, I would suggest inspecting your house for signs of damage. Furniture and trim are the main hardwood items in a house. But since it packs its frass in the galleries, you might not see signs of damage until the adult exit holes appear. Varnished wood surfaces would probably be protected from egg-laying, but cracks and crevices with untreated surfaces are where eggs would likely be laid. This species is attracted to lights, but finding multiple specimens inside your house probably indicates that they are coming from indoors. If you have firewood in the house, that may be the most likely source. Storing the firewood outside the house would be best. If any furniture is infested, a good treatment option is chamber fumigation for those items, which can be done by many of the larger pest control companies.