Silverfish are nocturnal insects typically 13–25 mm long. Their abdomens taper at the end, giving them a fish-like appearance. The newly hatched are whitish, but develop a greyish hue and metallic shine as they get older. They have two long cerci and one terminal filament at the tips of their abdomens; the filament projects directly off of the end of their body, between the left and right cerci. They also have two small compound eyes, despite other members of Zygentoma being completely eyeless, such as the family Nicoletiidae.Like other species in Apterygota, silverfish are completely wingless. They have long antennae, and move in a wiggling motion that resembles the movement of a fish. This, coupled with their appearance and silvery scales, inspires their common name.Silverfish typically live for two to eight years.[4] Silverfish are agile runners and can outrun most of their predators (including wandering spiders and centipedes).

While the Silverfish breeds optimally in temperatures of 22°C to 27°C, the Firebrat tends to select furnace rooms and walls near radiators or steam pipes, where the temperature range is between 27°C and 41°C. They feed quietly on starchy things like glue and bread crumbs, as well as textiles and a variety of other foodstuffs and leave holes in the materials they feed on. A common place to find them is in wash basins and bath tubs. Three species of Silverfish are found in Ontario, along with the Firebrat. They have three long sensory features attached to the bind end of the body.