Thysanura range in size from 0.5 to 2.0 cm. They have carrot-shaped bodies with 3 long segmented tail filaments. The filaments are bristled. They also have 2 cerci (singular: cercus) which can be mistaken for legs, see the image below. They run very fast and are difficult to catch, and as they are covered in shiny scales they are aptly named silver fish. They undergo many moults - even as adults which is very unusual for an insect. They may live for as long as five years, and take around a year to reach maturity.

Silverfish usually live in buildings in colder climates, and the females can lay eggs throughout the year. The eggs hatch in around 2 weeks and reach maturity in just 3 months.