Silverfish are very primitive insects, as proven by being found in fossils.
In Australia, there are 28 described species of silverfish, and about five of these species have successfully invaded buildings. Silverfish are agile, fast-running, scale covered, wingless insects.
The household pest species restrict their activities to relatively undisturbed areas (eg. book cases, storage rooms/areas) where they may damage fabrics, paper and other materials.
Structure
Silverfish are wingless and have a flattened, slender, scale covered body. The structure of the young is similar to that of the adult. Most have a silvery appearance and the body tapers to the rear. Antennae are usually long and slender, and three long appendages from the rear of the abdomen are very conspicuous.
Life Cycle
Females lay eggs singularly or in small batches which can be between 50-100 eggs, and these usually hatch in 2-8 weeks. The hatchlings closely resemble the adult form and undergo a number of moults to obtain the adult length of between 10-15mm. Usually, sexual maturity is reached after three months. Silverfish continue to moult periodically throughout their adult life, which may be as long as 4 years.
Habits
Silverfish are agile, fast running, nocturnal insects that generally shun light. They are usually found in dark, undisturbed places, but may range fairly widely throughout dwellings. Their inability to climb smooth surfaces often results in them being trapped in bathtubs and basins.
Silverfish as Pests
Within buildings, silverfish may be found almost anywhere within. While often found in roof voids in Melbourne, they may also occur in wall voids, subfloor areas and many places within the dwelling parts of the premises. They feed on most types of human food, but seem to prefer starchy materials. When paper or photos are attacked, it is often the outer, shiny layer that is most damaged. Book bindings, cottons, linens and wallpaper are often damaged. Any sources of glue, starch or cellulose are likely to be attractive.
Control of Silverfish
Because silverfish can be quite widespread within a dwelling, inspection is an important prerequisite to treatment. Thorough inspection should involve moving stored articles to reveal disturbed silverfish. The possibility of populations residing in wall cavities can make control more complex and demanding.
Non-chemical methods of prevention and control
Inspecting incoming goods that may harbour silverfish (eg. secondhand books and boxes from storage areas) may help to avoid infestation. Where possible, books, papers, files and photos, should be stored in light and airy conditions. Books hidden away in closed cabinets, particularly if infrequently opened, can provide very suitable conditions for silverfish development. In kitchen areas, tight containment of foods and frequent cleaning of scraps and crumbs help to reduce the suitability of that environment to silverfish.
Chemical Control
Owing to the often widespread distribution of silverfish within premises, it is usually necessary to use a combination of treatments to achieve effective levels of control.
Where possible, particularly in conditions of poor hygiene, a clean up prior to insecticide application can be most beneficial.
Preferred types of insecticide application:
Surface-sprays: Low or non-hazardous chemicals of the synthetic pyrethroid type. Where it is safe to do so, these residual surface sprays should be applied to surfaces on which the silverfish rest or travel.
Mists/fogging/high pressure aerosols: Low or non-hazardous chemicals of the synthetic pyrethroid type. Use of space sprays can be a useful backup to surface spray applications. Applied properly, non-residual insecticides can be distributed in the spaces of a building to control silverfish that may escape contact with treated surfaces.
Dusts: Dry dust formulations can be useful in silverfish control. Often the areas in which silverfish dwell are not suited to wet sprays (eg. libraries, archives, files).
Dusts applied to surfaces tend to leave a very fine layer, which can give good residual control. Ceiling voids, which often serve for silverfish harbourage, can be safely and efficiently treated with dusts.