If you’ve ever seen a small, silvery bug dart across your bathroom floor, you’ve probably met a silverfish. These prehistoric, wingless insects—about 1½ inches long—move with a wiggly, fish-like motion. They don’t bite or spread disease, but they can damage books, wallpaper, and clothing. Why They Invade Silverfish love moisture, darkness, and carbohydrates. Bathrooms, basements, kitchens, and laundry rooms provide...