Getting to Know Booklice

What are Booklice?

Booklice are small insects, officially known as psocids. The name booklice originated because they are often discovered in books and have a similar appearance to lice. They are not actually related to lice however, and are not parasites. While booklice are known for being inside homes, there is actually another type of psocid that lives outdoors and is known as barklice. As the name implies, bark lice infest trees. Interestingly, bark lice don’t actually damage the tree and do not need to be treated.

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What do Booklice Look Like?

Booklice are oval shaped with a soft body and typically range from 1 to 2 mm in size. Colors of booklice can vary from pale to brown, with some having a striped appearance. Booklice living inside the home are wingless, and cannot jump. They simply run from place to place.

Getting to know Book Lice

By Tony Wills [CC BY-SA 3.0 (http://], via Wikimedia Commons

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What Conditions Do Booklice Live In?

The ideal conditions for book lice is hot with a humidity level between 75% and 95%. In these conditions, booklice will reproduce quickly with females laying approximately 60 eggs during the summer months. Furthermore, if the temperature and humidity are high, book lice can speed through the life cycle in about a month. When the weather cools down, less eggs are laid and the life cycle extends.

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What Do Booklice Eat?

Booklice feed on mold, mildew, algae and yeast. This means that they could be discovered anywhere these conditions are present. The obvious option is books, especially if they are not moved often or are in storage. In addition to books, booklice could be found throughout the home in furniture, rugs, windowsills or even under wallpaper. Booklice may also be discovered in the kitchen. They love feeding on pantry items such as grains or flour, especially when the items are damp.

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Are Booklice Dangerous?

Booklice do not pose much of a threat to humans, since they don’t spread diseases or bite. However, it’s also not ideal to find an infestation of booklice in your home as they could cause damage or waste. For instance, if you find booklice in cereal or flour, you will have to dispose of the items. Over time, booklice can also damage or ruin books, paper goods, home furnishings and more.

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How Do You Prevent Booklice?

Since booklice need some sort of mold or mildew to survive, the best method for prevention is to not let mold spread in your home. There are a couple of ways to accomplish this. First, maintain a consistent humidity level that is below 60% relative humidity. This is where a dehumidifier can be helpful. Good ventilation and a moderate temperature are also useful for preventing mold growth. Furthermore, practice good sanitation throughout your home. For instance, don’t leave food sitting out and keep pantry items dry and covered.


Dellinger, Theresa A, and Eric Day. Psocids: Barklice and Booklice. Virginia Cooperative Extension, 2015, PDF.pdf. Accessed Aug. 2017.

Jacobs, Steve. “Booklice (Department of Entomology).” Department of Entomology (Penn State University), Penn State College of Agricultural Sciences, Jan. 2014, extension/factsheets/booklice. Accessed 17 Aug. 2017.

Merchant, Michael. “Mildew-Feeding insects in the home.” Insects in the City, Texas A&M, Accessed 17 Aug. 2017.