April 1, 2003
By: Kyle Jordan
are 13 silverfish species in the United States, though only a
few are pests. Some other names for them include the bristletail
(which is actually an insect from a different order, Microcoryphia)
and the fishmoth.
The common silverfish, Lepisma saccharina (Linnaeus), the fourlined
silverfish, Ctenolepisma quadriseriata (Packard), and the gray
silverfish, Ctenolepisma longicaudata (Escherich), are the main
pest species. The common silverfish is dark gray with a metallic
sheen. The fourlined silverfish is dark gray and has four lines
running the length of its body. It also has three pairs of styli
(small projections that resemble the tails, but are much shorter)
on the rear of its abdomen. The gray silverfish is uniformly gray
and has only two pairs of styli on the rear of its abdomen. The
common and the gray silverfishes reside mainly indoors, while
the fourlined silverfish also will live outdoors in mulch or under
All silverfish have the characteristic carrot- or teardrop-shape
and three caudal appendages. Silverfish antennae are threadlike,
and can be as long as the body. At maturity, silverfish may be
about one-half inch in size, and with the tails can reach almost
The common silverfish lays one to three eggs almost daily, while
the gray silverfish lays eggs in clusters of two to 20 and places
them in cracks and crevices. The fourlined silverfish is thought
to have similar egg-laying habits to the common species.
Silverfish do not undergo metamorphosis - the young look like
the adults, and adult silverfish can molt even after they are
mature. One species is reported to have up to 59 molts in a lifetime.
The scales that give the silverfish its gray, metallic appearance
develop after the third or fourth molt. Usually, it takes three
to four months for a silverfish to reach maturity, but in cool
environments, it can take much longer to develop - sometimes several
Silverfish like to feed on objects that contain proteins and
carbohydrates. Different species of silverfish prefer different
ratios of the two - the common silverfish prefers proteins to
carbohydrates, and the gray silverfish feeds on carbohydrates
and proteins, but prefers foods with high cellulose content.
This affinity causes them to target fabrics, such as artificial
fabrics and cotton, and linen, but not wool or real silk, paper
products (wallpaper, cellophane, facial tissue, etc.) and stored
dried foods. The fourlined silverfish and the gray silverfish
are able to consume cellulose-rich foods - the former because
it produces the enzyme cellulase, and the latter because its mid-gut
contains cellulose-digesting bacteria and enzymes.
Damage caused by silverfish can be etchings (like someone has
scraped the surface with their fingernail), holes or notches.
Yellow fecal stains and discarded scales also are telltale signs.
Once they find a food source, silverfish tend to remain close
to it. Though they can go for weeks without food or water, they
often are discovered in sinks and tubs, where they become trapped,
having crawled in searching for a source of moisture. Room temperature
and high humidity are preferred, but silverfish can be found in
any room of a house or in the mulch or leaf litter around a house.