Psocids are only about 2-3 millimeters long and are often overlooked by the naked eye. They are sometimes referred to as booklice when found among old books and other paper products that have been stored in a dark damp area; or as barklice when found in decayed trees, mulch, or on firewood. These pests prefer a warm and damp habitat and, therefore, are more numerous in the spring and summer months.
Eradicating the presence of psocids from your home can sometimes be tricky. Psocids mainly feed on mold and mildew. The ongoing presence of psocids in a particular area is a good sign that wet wood and/or damp paper products are also in that area. These items should be removed or dried out, and the source of moisture be found and eliminated. Common problem areas are window casings, plumbing leaks, cardboard boxes on a concrete floor, a basement room with high humidity, etc.. Try to organize any stacks of books or cardboard boxes in a way air can circulate around them. A dehumidifier should also be considered as a part of the solution.
Most pesticides you can buy at the hardware store will be effective at killing psocids, but, the elimination of moisture, mold and mildew is the best solution for long term control.