Silverfish (likely)

Warm, dark, humid places such as bathrooms, basements, wall voids, and stored-paper areas; this individual appears outdoors on masonry.

Feeds on carbohydrates and starches in paper, book bindings, wallpaper paste, textiles, and crumbs; it may also consume mold and dead organic matter.

Fast-running, wingless, and mainly nocturnal; it hides in cracks during daylight and develops gradually through successive molts without a pupal stage.

Harmless to people and not known to transmit disease or bite. Indoors, it can damage paper, books, fabrics, and adhesives; ecologically, it helps recycle organic debris.