I got a mattress on Craigslist to cushion something large and have been storing it in the barn (not house) and recently noticed that it is covered with small (3-4 cm) insects that have spread to other parts of the barn. They don't look like photos of bedbugs: they aren't oval or flat, and they aren't 5-7 cm. I looked through a magnifying glass and they seem to have a head, thorax, and abdomen rather than a flat shell, though they are so small it is hard to tell for sure. Does anyone know what they might be?

How long does it take for bedbugs to naturally die in an uninhabited house with no hosts?