Silverfish / Firebrats
The name Thysanura, derived from the Greek "thysano-" meaning fringed and "ura" meaning tail, refers to the long, fringed filaments on the abdomen of silverfish.
Classification & Distribution
- lacking metamorphosis
- eggs hatch into young which are smaller than adults, but similar in appearance.
- primitively wingless
Distribution: Common in domestic and sylvan habitats worldwide.North America
Number of Families35 Number of Species18~370
Life History & Ecology
Silverfish are fast-running insects that hide under stones or leaves during the day and emerge after dark to search for food. A few species are resistant to desiccation and well-adapted to survive in domestic environments such as basements and attics. Silverfish are scavengers or browsers; they survive on a wide range of food, but seem to prefer a diet of algae, lichens, or starchy vegetable matter.
Thysanurans may be rather long-lived -- three years is probably typical and up to seven or eight years may be possible. They continue to molt frequently, even after reaching adulthood.
Silverfish have an elaborate courtship ritual to insure exchange of sperm. The male spins a silken thread between the substrate and a vertical object. He deposits a sperm packet (spermatophore) beneath this thread and then coaxes a female to walk under the thread. When her cerci contact the silk thread, she picks up the spermatophore with her genital opening. Sperm are released into her reproductive system, and then she ejects the empty spermatophore and eats it.
Physical FeaturesAdults and Immatures
- Body relatively flat, tapered and often covered with scales
- Compound eyes small or absent
- Antennae long, thread-like, and multisegmented
- Abdomen with ten complete segments
- Eleventh abdominal segment elongated to form a median caudal filament
- Cerci present, nearly as long as median caudal filament
- Styliform appendages located on abdominal segments 7-9
Domestic species such as silverfish and firebrats may cause extensive damage to household goods. They often feed on wallpaper paste, bookbindings, and the starch sizing of some textiles. Cardboard and other paper products may also be damaged.
- Lepismatidae -- Most of the North American species belong to this family, including the silverfish (Lepisma saccharina) and the firebrat (Thermobia domestica).
- Firebrats have been known to live more than 6 years -- through 60 instars. It has been suggested that frequent molting is an adaptation that reduced the risk of infection by parasitic fungi.
- One family of Thysanura (Nicoletiidae) is adapted to live underground in caves, mammal burrows, or in the nests of ants or termites. Some species mimic ants and steal their food.
- For many years, the family Lepidotrichidae was known only from Oligocene fossils. It was thought to have been extinct until 1959 when living specimens were discovered in northwestern California.