A book lover’s eternal enemy!
Chances are, you are sharing your home with a host of living fossils. Puzzled? You heard right. The silverfish (Lespisma saccharina) in your home belong to the world’s oldest family of insects. Their unchanged appearance goes back some 300 million years.The flightless soft and silvery half-inch insects who love to crunch on your books belong to the order archaeognatha, which also includes the wingless ‘jumping bristletails’, a cousin who lives outdoors and who can leap two feet in the air. Check out a photo of a jumping rock bristletail and you will find many familial resemblances. Their form it appears is so perfected there was no evolutionary necessity for an alteration of the original prototype cast so far back in time.
Like the jumping bristletails, silverfish have six legs, no wings, two long antennae protruding from the head, and three long feelers protruding from the thorax. They are said to be the most primitive of insects, prehistoric: hence the moniker “living fossil”.
In present times, however, they are a book lover’s eternal enemy. When mankind moved on from stone tablets to starchy paper books, they discovered a gourmet treat. My father-in-law who loves books says his beloved library has three threats: borrowers, borers, and silver fish. He discovered swarms of the latter recently when spring-cleaning his book collection, which includes valuable old books. Of course, none were to be seen during the day because silverfish are photophobic and flee from any form of light. But turn a few pages, and one might slide out to quickly disappear into the binding. Telltale marks of their presence are grainy balls of faeces, sort of like miniature pepper corns, thinning pages and of course holes with yellowed edges.
They love starchy foods
The word saccharina refers to silverfish’s preferred polysaccharide diet of starchy substances like book bindings, carpets, cardboard, dandruff, glue, pasta, paintings and cloth, although it can extend to just about anything, from meat to toe nails in times of scarcity. They don’t bite us, drink our blood or spread disease, but they do pose a serious threat to the contents of your wardrobe, bookshelves and food stocks. Because they are so small, hide away in tiny crevices and emerge in the cover of dark, they are hard to get at. Because they have dry outerskins, they tend to like somewhat damp places. They live not only in bookshelves and libraries, but in kitchens, bathrooms and in fact any dark, damp corner near a food source.
“Books in libraries give them the ideal home to breed and feed,” says Raja Mahendran, expert in agro and urban pest control and consultant to global pest control organisations. “The warmth and humidity are perfect. Their enemies will be better aeration, brighter sunlight/lights, frequent dusting of books and brushing away the nooks and crannies of bookshelves.”
The tropics are perfect for breeding
Controlling silverfish is not easy. Hot humid climes are perfect breeding conditions. Unlike mosquitoes and flies, these insects do not pupate, but go through three developmental stages – egg, nymph and adult. They are incredibly resilient, being able to survive without food and on just water for as long as a year. When time comes to find a partner, silverfish go through a charming little mating ritual, where the courting couple face each other and repeatedly advance towards and retreat from each other. Then the male moves on, leaving the female to rush after it. The male drops a bag of sperm, which the female picks up and uses to fertilise her eggs. Silverfish can live from two to eight years, a long time for such a little creature. They reach adulthood in two years, and continue to grow until death. An adult female lays two to twenty eggs daily for the rest of her life, and so they flourish.
“Professional pest controllers generally fumigate with methyl bromide or phosphine gas,” says Mahendran. “Books and shelves are covered with gas proof sheets and are penetrated by the gas. In the West, however, the entire building will be covered with gas proof sheets.”
Fumigation does not give residual control, he adds. This means that some silverfish will survive to breed again another day. To make the treatment effective, it has to be repeated twice or thrice a year.
Mahendran cautions: “Before signing on the dotted line, make sure your Pest Control professional has a fumigator’s licence because a mere pest control licence is insufficient for fumigation, which requires a lot of safety measures in order for it to be safe and effective. Also, people should not confuse fogging with fumigation. Fogging reaches areas inaccessible manually, but is not as good as fumigation.”
Large institutions like libraries and archives have a huge range of options. One is gamma radiation, which however has been found to damage cellulose, the building blocks of paper. Heat and freeze treatments are also used. Freeze treatments have to be long, over 72 hours perferably, but the dampness during thawing can damage books.
Mahendran endorses the following home treatments:
- Boric acid sprinkled along boards, under bathtubs and any areas that show signs of their presence – tiny pepper-like black droppings, yellowing holes in books, dead silverfish and moult droppings. Boric destroys both silverfish and eggs, but because it is toxic, can be harmful to humans if inhaled. This means you shouldn’t sprinkle boric and then turn on the fan in your library.
- Sprays containing liquid pyrethrin can be sprayed along baseboards and into cracks and other silverfish hideouts. However, don’t use it in the kitchen or where it could harm pets because it is toxic.
- Homemade silverfish traps are easy to make – dampen a newspaper, roll it up and loosely tighten either end with a rubber band. Leave it on or near your bookshelf through the night. In the morning, pick it up, quickly secure both ends and put it in a plastic bag. Dispose of it far from your home. There are other traps… trawl the Net to learn how else you can trap them.
- Citrus sprays, lavender oil, and mothballs are also said to deter them. Store them among your books and clothes.
- Spices like cloves, cardamom and cinnamon put off silverfish who do not like the heady aroma. Make little sachets of these spices and place them on your bookshelves and in your wardrobe and drawers. Or burn clove essential oil in your library.
Remember that these solutions may help get rid of some of the problem, but not all of them. Female silverfish leave behind lots of progeny. If you are a serious book collector, you may have to consider other more thorough options.