“Bookworm” isn’t a single insect. It’s a catch-all term for several pests that bore through, chew on, or nibble the edges of books. The most common culprits are silverfish, booklice, carpet beetle larvae, and certain moth larvae. Getting rid of them requires killing the insects already present, then changing the environment so they don’t come back.
Identify What’s Eating Your Books
Different pests leave different evidence, and knowing which one you’re dealing with helps you target your response.
Silverfish are slender, silver-gray insects about half an inch long that move in a fish-like wiggle. They feed on the starchy polysaccharides in paper and binding glue. Paper that looks slightly ragged or scalloped at the edges is usually their work. They’re nocturnal, so you may spot them darting away when you pull a book off the shelf at night.
Booklice (also called psocids) are tiny, soft-bodied wingless insects, often 1 mm or smaller. They don’t actually eat paper directly. Instead, they feed on the microscopic mold that grows on books stored in humid conditions. If you see what looks like fine dust moving on a book’s surface, you’re likely looking at booklice.
Beetle larvae cause the most dramatic damage. Of the quarter million species of beetles, several target books. Adults lay eggs on a book’s edges and spine, and when the larvae hatch, they bore into and sometimes completely through the pages, leaving round tunnels. Drugstore beetles and deathwatch beetles are frequent offenders.
Moth larvae and even cockroaches can also chew through books, though they tend to cause surface damage rather than deep boring.
Kill Active Infestations With Freezing
Freezing is the safest and most effective way to kill book pests at every life stage, including eggs. Museums and archives worldwide use this method because it destroys insects without exposing books to chemicals that could damage paper or bindings.
You need a chest freezer that reaches at least -20°C (-4°F). Standard kitchen freezers with auto-defrost cycles won’t work well because they periodically warm up, which lets some eggs survive. A basic chest freezer without auto-defrost is ideal.
Here’s how to do it:
- Seal the books in plastic bags. Use zip-lock bags or wrap them tightly in polyethylene sheeting. This prevents moisture from condensing directly on the pages during freezing and thawing.
- Place the sealed books in the freezer. Don’t stack them so tightly that cold air can’t circulate around each bag.
- Leave them for a full two weeks. Do not open the freezer during this time. The prolonged exposure ensures that eggs, larvae, and adults are all killed.
- Thaw slowly. After two weeks, remove the bags but leave them sealed until the books reach room temperature. This prevents condensation from forming on cold pages.
For a small number of books, this is completely doable at home. If you have a large collection with widespread damage, you may need to process them in batches over several weeks.
Vacuum and Clean the Shelves
While your books are in the freezer, clean the area where they were stored. Vacuum the shelves thoroughly, paying attention to corners, crevices, and the wall behind the bookcase. Insect eggs can lodge in tiny gaps in wood grain or between shelf boards. Wipe shelves down with a damp cloth and let them dry completely before replacing any books.
If you’ve been storing books in cardboard boxes, get rid of them. Insects love corrugated cardboard both as a home and a food source. Replace damaged boxes with acid-free, lignin-free archival boxes if you need enclosed storage.
Drop the Humidity Below 50%
Humidity is the single biggest factor that makes a book collection vulnerable to pests. Booklice die within weeks when relative humidity stays below 50%, because the mold they feed on can’t grow in dry air. Silverfish and beetle larvae also thrive in damp conditions and struggle in drier environments.
Measure your room’s humidity with an inexpensive hygrometer (available for under $15 at most hardware stores). If your reading room, closet, or storage space consistently sits above 60% relative humidity, you have ideal conditions for an infestation. Your goal is to keep it reliably below 50%.
A dehumidifier is the most straightforward fix. In smaller spaces like closets, desiccant products (silica gel canisters or moisture-absorbing tubs) can help. Air conditioning naturally lowers humidity too, so climate-controlled rooms are inherently safer for books. If your home is consistently humid, especially in basements or rooms without ventilation, consider moving your collection to a drier area of the house.
Improve Airflow Around Your Books
Stagnant air traps moisture and creates microclimates where mold and insects flourish. The environment most damaging to book collections, high humidity combined with poor air circulation, is also the most beneficial to pests.
Don’t push bookshelves flush against exterior walls, especially in older homes where walls may transfer moisture. Leave a gap of a few inches. Avoid packing books so tightly on shelves that air can’t move between them. If a room has no windows or vents, even a small fan running periodically helps prevent the still, damp pockets that pests need.
Protect Valuable Books Long-Term
For books with real monetary or sentimental value, archival storage adds a physical barrier against future infestations. Acid-free enclosures (clamshell boxes or archival wraps) fitted with tight seals keep insects from reaching the paper in the first place. Museums use display cases with gaskets for exactly this reason.
Regular inspection is your best ongoing defense. Pull books off the shelf every few months and check the spines, edges, and gutters for frass (fine powdery debris that looks like sawdust), tiny holes, or live insects. Catching a new infestation early, when only one or two books are affected, means you can freeze just those volumes instead of treating an entire collection.
Keep food and drinks away from bookshelves. Crumbs attract cockroaches and other generalist feeders that will chew on books opportunistically. Dust your shelves regularly, since accumulated dust holds moisture and provides a foothold for mold growth, which in turn attracts booklice. A clean, dry, well-ventilated bookshelf is an environment where book pests simply can’t establish themselves.