Pest Profile: Silverfish

Silverfish are in the order Zygentoma. This soft-bodied insect is a voracious feeder on items high in starch, glue, and cellulose. For example, they are common in libraries and museums where paper books and labels are abundant. However, they can also be found outdoors in cool shaded places, such as under leaf litter, under rocks, in caves, and even in ant nests. Similar to other insects found in homes, silverfish can be found worldwide.

The Hidden Pest in Your Bookshelves

Silverfish are silver or light pearl gray in color and are covered with glistening scales. Their soft bodies are wingless and about 0.85 cm in length. They have two long antennae, and their body is wider at the head and tapers down to the end where there are three long bristle-like appendages. Silverfish are nocturnal and not often seen during the day unless they are disturbed. Silverfish have one of the simplest life cycles of all insects. They have what is called an ametabolous life cycle, also referred to as “without metamorphosis.” This is because unlike some insects, such as a butterfly, which has four distinct life stages (egg, caterpillar/larvae, chrysalis/pupa, and adult/butterfly) which all look different, the silverfish do not have uniquely identifiable life stages. The adult silverfish will lay an egg, and from the time the young hatch, they look like miniature adults. The young will molt 6 to 7 times until they become adults. Adults will continue to molt throughout their life; however, there is no set number of times that they will molt. If conditions are favorable, these insects can continue to molt for as long as four years.

When found indoors, they are usually found in areas with high humidity and controlled temperatures. As such, they can pose a large problem for commercial businesses such as museums and libraries which have not only significant food sources but also controlled climates. Other common indoor areas where silverfish may hide are kitchens, bathrooms, attics, and basements. How do we help to eliminate these pests? The best way to help control infestations of silverfish is through reducing humidity and employing physical control methods. These physical measures include sealing cracks and holes in which silverfish can be found, removing standing water, and removing paper products from cool damp environments.

Kristen Stevens, BCE