How or why do silverfish appear?

[1] Silverfish like to eat carbohydrates such as starches and sugars. They easily find that diet in the moisty dark places inside houses; from the conditions and products that can be found in basements, bathrooms, and kitchens; and among the objects found in houses, such as the glue in book bindings. [2] They get in through cracks, crevices, and wall voids. [3] Boric acid can be used in wall voids, pyrethrin elsewhere. [4] Not too much can be done about books. That's just the way they're made. But elsewhere, it's important to free corners and dark spots of clutter, dark, and moisture.