Silverfish, scientifically known as Lepisma saccharinum, and various species of cockroaches are two of the most common insect pests found in human dwellings. Both thrive in similar indoor conditions, seeking dark, secluded, and humid environments within homes. Because they frequently share the same habitat, people often wonder if one pest might naturally control the population of the other. The specific question of whether the small, silvery, wingless silverfish might prey upon the larger cockroach deserves examination.
The Relationship Between Silverfish and Cockroaches
Silverfish are not predators of cockroaches, nor are cockroaches predators of silverfish. Silverfish lack the physical attributes and predatory instinct necessary to hunt and subdue a live cockroach, which is often significantly larger and faster. Their interaction is primarily defined by competition for the limited resources of water and shelter found indoors, rather than a predator-prey dynamic. Both insects require high humidity levels to survive, often coexisting as scavengers in damp, dark spaces like basements, bathrooms, and utility closets.
Silverfish are omnivorous detritivores, meaning they consume decaying organic matter and dead insects. A silverfish may occasionally consume the remains of a dead cockroach or its molted exoskeleton as a source of protein and nutrients. This behavior is scavenging, not predation, and it does not impact the overall cockroach population. The presence of silverfish does not function as a biological control for a cockroach problem.
The Actual Diet of Silverfish
The silverfish diet explains why they are not interested in live insect prey. Their scientific name, saccharinum, is derived from their strong preference for foods high in carbohydrates, specifically starches and polysaccharides. They are equipped with the ability to digest cellulose, a polysaccharide found in plant cell walls, which few other insects can do efficiently. This specialized digestive capability drives them to consume a variety of household items rich in these compounds.
Common household targets include materials like paper, cardboard, book bindings, and wallpaper paste, all of which contain starches and dextrin. They also seek out fabrics such as cotton, linen, silk, and rayon, often damaging clothing and upholstery. Beyond structural items, silverfish consume human detritus like dead skin flakes, hair, and dried pantry goods such as flour, oats, and dry pet food. Their scavenging diet is focused on these nutrient-rich, non-living materials, leaving live cockroaches completely outside their dietary interest.
Managing Infestations in Shared Habitats
Since both silverfish and cockroaches thrive in high-moisture environments, managing an infestation involves environmental control focused on reducing humidity and eliminating shared food sources. The most effective step is reducing the indoor relative humidity to below 50-60% throughout the structure, especially in basements and bathrooms. This can be achieved by using dehumidifiers, ensuring proper ventilation with exhaust fans, and promptly repairing any plumbing leaks. Removing the moisture makes the habitat inhospitable for both pests.
Eliminating accessible food sources is also highly effective. All dry pantry goods, including flour, grains, and pet food, should be stored in hard plastic or glass containers with airtight seals. Reducing clutter like stacks of old newspapers, books, and cardboard boxes removes their primary food and shelter sources. Sealing cracks and crevices in baseboards, walls, and shelving acts as a physical barrier, preventing both species from accessing their preferred secluded harborage areas.