What are Silverfish?

Silverfish are the fishmoth species Lepisma saccharina. These eight-legged insects have scales on their bodies that allow them to move in a quick, curving manner that resembles that of a fish. They have a silver or gray coloring, but some also have a brownish cast. Most are between 0.5 inch (12.7 mm) to 1 inch (25.4mm) in length and they have very long antennae as well as three thread-like protuberances from their lower bodies. Silverfish live outdoors in damp, rocky or moldy areas, but easily thrive indoors in humid rooms such as bathrooms and are considered urban pests.

These insects were native to tropical climates before spreading to damp, cooler regions. Females lay up to 50 eggs at once, but only lay about 100 eggs during their lifespan. The lifespan of a silverfish is generally between two and eight years. They have soft bodies and are wingless. Silverfish can climb rougher surfaces, but not usually slippery surfaces and, as a result, they are sometimes found trapped in sinks and bathtubs.

In homes, silverfish tend to live behind baseboards around floors, or near plumbing and pipes in small cracks. Besides bathrooms, and sometimes kitchens or closets, silverfish can be found in crawlspaces and attics. Their eggs are often found in boxes of old clothing and books as silverfish eat the starch in fabrics and book paste. They are nocturnal insects and often prefer dark areas.

Vacuuming often, especially around baseboards, can help control the spread of silverfish in a home as it can eliminate the tiny eggs. Cracks and crevices around baseboards should be washed and dusted often to help reduce the population. Killing their eggs and removing their food sources are the best ways of controlling them.

Traps can also be put in areas where silverfish have been seen. A person create a trap by covering a small, open jar with masking or other fairly rough-textured tape. The insects will be able to climb into the jar, but not out again due to the slippery surface of the inner glass. A damp newspaper rolled up into a hollow shape may also serve as a silverfish trap.

Diatomaceous earth, a powder made up of crushed algae-like organisms called diatoms, is found in many pesticides, but is not harmful to the environment and is non-toxic to humans and pets. Homeowners can buy diatomaceous earth inexpensively in bags at garden centers and sprinkle it around baseboards where they have seen silverfish. People should wear a protective mask when working with the powder, as any dust-like substance can irritate the eyes and nose when it is not yet settled.