Silverfish and firebrats are primitive insects that are as long as 1/2 inch. They have gradual metamorphosis, which means the young are small versions of the adults. Both are covered in silvery to brownish scales and have a carrot shaped body that tapers to the tail end with 3 bristles or hairs. They have no wings, but the antennae are long and threadlike, and the legs are visible. Silverfish and firebrats run fast and hide in small crevices.

Silverfish prefer areas of high humidity and warmth. They are commonly found in attics and wall voids. Firebrats like warmer areas and may be found near boilers or furnaces. They lay batches of eggs in crevices and go from egg to adult in 2 to 4 months. Silverfish and firebrats can live for 1 to 2.5 years and survive for a year without food.

Silverfish and firebrats are common in homes, libraries, archives, museums, food establishments, and warehouses. They feed on paper, wallpaper, and book bindings, especially the starchy or protein-based glues on these items. Firebrats will also feed on flour and other grain dusts. They can cause damage to items through feeding or staining from their excrement. Silverfish are a nuisance when seen in homes. Firebrats appear more often in commercial bakeries and industrial settings.