These bugs feed on boxelder trees. In the fall they like to surround the lower tree areas closer to the ground. Once winter hits they look for hiding places. They then can get through the foundation cracks and eventually end up in your home. They start emerging during the spring and this means they can be found in your home.
Boxelder bugs do not bite and are about half an inch. They also do not reproduce inside homes, but they can group together and start coming in through the same crevices.