Margit Smith, Independent scholar, USA

The dreaded Lepisma saccharina

Although unable so far to find a monetary value placed on the damage inflicted by infestations of silverfish in libraries, archives, paper storages etc. it is well known that they are responsible for severe deterioration of paper-based items. Found throughout most areas on the globe, they are easily transported in shipments of paper and cardboard, are not always readily detected, as they are mainly nocturnal, and are difficult to eradicate.

Silverfish belong to the so-called Ur-insects, meaning they are of ancient origin (over 300 million years old) and in contrast to most other insects do not possess wings. To have survived as long as they have in such diverse environments, they had to develop adaptive capacities to withstand extreme conditions. Adults may be able to survive for over 300 days without nourishment and reach an age from two to five years. Females lay between 70 and 150 eggs, mainly in dark, warm and damp environments, but have also been found to infest birds’ nests.

In addition to damaging paper-based objects, silverfish are considered detrimental to human hygiene as they can infest flour, semolina, oatmeal and other starch and sugar containing foodstuffs. In this way they may contaminate the foods with human pathogens and lead to serious diseases. A silverfish relative, Thermobia domestica is less common and lives mainly in bakeries.

Damage inflicted by silverfish ranges from slight abrasion produced by grazing over the top layer of paper in a rasping fashion, to the point of eating through the paper. In especially advanced stages of destruction the book or page begins to resemble a piece of lace and can crumble when picked up. In some cases the damage is confined to one element of a page, e.g. only the white ink of printed letters was attacked on one book cover.

The first defence against silverfish is cleanliness of storage areas to remove any dust and debris such as accumulate from the action of shifting books and papers. Since silverfish eat microscopic mold on plaster walls and drywall materials, keeping walls dry and free of mold is of utmost importance. All packing materials used in the transport of books etc. should be destroyed, not re-used as silverfish prefer to lay eggs in folds, creases and the corrugated walls of cardboard boxes. Materials received from overseas areas, especially those with tropical climates, should be put into a quarantine room for a while where frequent checking for silverfish eggs and dust-like droppings can be carried out.

In the US a product called DekkoPak is available and is very effective in addressing silverfish infestations. It contains 20% boric acid and 80% inert ingredients. The paks are approx.. 2 ½ x 3”, are constructed of a layer of corrugated paper which contains the borax, between two layers of plain paper; they are open on all four ends. The packs attract the silverfish, they ingest the borax that dries out their gut and kills them. I have also heard of other home-made remedies, mainly mixing borax with baking powder and some sugar to attract them, and placing this powdery substance in areas where silverfish are found. This may not be applicable to the more formal settings of libraries, archives, museums, etc., however various insect trapping products can be used. To my knowledge, however, only DekkoPak is especially formulated against silverfish.

My presentation will provide information about silverfish on the above mentioned points, namely:

• their appearance
• on what they feed
• their life-cycle
• the damage they cause
• the ubiquity of the silverfish worldwide
• how they are transported
• their preferred environment
• the damage they inflict
• how to control them

Supported with photographs and other visuals, this presentation is germane to the Conference as it speaks to a practical aspect of preserving manuscripts, printed books and other paper-based items.