When books, documents, or wallpaper show signs of damage, the cause can often be traced back to insect pests. Paper is primarily composed of cellulose, a complex carbohydrate derived from wood pulp, but it is not the pure cellulose itself that attracts most insects. Rather, the various additives, coatings, and adhesives used in paper manufacturing and bookbinding provide an appealing food source. Understanding the specific insects involved and the nature of the damage they inflict is crucial for preservation.
Identifying the Primary Paper Eaters
The most direct threats to paper are the insects whose digestive systems are adapted to process the starches and sugars applied during production. Silverfish (Lepisma saccharinum) are distinguished by their wingless, silvery-gray bodies and fish-like movements. These nocturnal insects thrive in dark, humid environments and produce the enzyme cellulase in their midgut, allowing them to digest the cellulose fibers found in paper.
Silverfish damage is characterized by irregular holes and surface grazing, often resulting in a ragged, lace-like appearance where the insect has scraped away at the paper’s surface. They are especially attracted to the dextrin and polysaccharide starches found in glues, bookbindings, and the sizing used to give paper its finish. A close relative, the Firebrat, causes similar damage but prefers warmer, less humid areas. Booklice, or Psocids, do not consume cellulose but feed on micro-organisms like mold and fungi that grow on damp paper. Their presence is a strong indicator of high humidity, and their feeding causes staining and surface abrasion.
The Nutritional Appeal of Paper
Paper’s fundamental structure is cellulose, a material that is difficult for most organisms to break down without specialized enzymes. The primary attraction for many paper-eating insects is not the wood pulp itself, but the various additives that make the material more palatable and easier to digest. These additives include starches and sugars, which are simpler carbohydrates used in glues, pastes, and paper coatings.
Sizing agents, which historically included animal glues or starches to improve ink absorption and paper strength, are particularly rich sources of these easily metabolized polysaccharides. Mold and mildew that flourish on damp paper also provide a significant draw for pests like booklice. These micro-organisms offer a readily available food source, and insects consume the mold spores, inadvertently damaging the paper surface.
Secondary Pests and Incidental Damage
Termites, belonging to the order Isoptera, are primarily focused on consuming wood structures, which are rich in cellulose. However, they readily consume paper and books that are in contact with their tunnels. These pests cause extensive damage by tunneling through materials, often leaving only the outer covers of books intact as they consume the inner pages.
Cockroaches are omnivorous insects that cause damage not by consuming the paper structure, but by feeding on the glues in bindings and the grime or food residue accumulated on books. They leave behind visible evidence in the form of dark fecal stains and oily secretions that contaminate the pages. Certain beetles, often referred to as “bookworms,” are the larvae of species like the Drugstore Beetle (Stegobium paniceum), and they bore tunnels through the paper and bindings while seeking dried organic material.
Protecting Documents and Books
Controlling the environmental conditions that attract and support insect life is crucial for preserving paper materials. Maintaining a stable environment is important, as fluctuations in temperature and humidity encourage decay and pest activity. Pest insects like silverfish and booklice require high relative humidity, generally above 60%, to thrive and breed.
Archival preservation standards suggest keeping relative humidity between 45% and 55% to discourage mold growth and insect proliferation. Temperature management is also a factor, with cooler temperatures, ideally between 65 and 72 degrees Fahrenheit, slowing down both insect life cycles and chemical deterioration of the paper. Storing documents in acid-free boxes and ensuring proper ventilation prevents the buildup of microclimates that trap moisture, which is a major attractant for paper-consuming pests. Good housekeeping, including the removal of dust, debris, and secondary food sources like spilled crumbs, further minimizes the appeal of a storage area to opportunistic insects.