The silverfish, Lepisma saccharinum, is a small, primitive, wingless insect belonging to the order Zygentoma. These creatures are classified as apterygotes, meaning they never developed wings throughout their evolutionary history. Their inability to fly is a defining characteristic, relying entirely on terrestrial locomotion. The common name, silverfish, comes from the insect’s metallic, silvery color and its distinctive, fish-like movements.
Distinctive Physical Features
The silverfish body is flat and narrow, tapering from the head to the rear in a tear-drop or carrot shape. This flattened structure allows them to easily access and hide within small cracks and crevices.
The body is covered in shiny, silvery-grey scales, which give the insect its metallic sheen. At the front, silverfish possess two long, thread-like antennae used for navigating in the dark. Their most distinguishing feature is found at the abdomen’s rear: three long, bristle-like appendages, known as caudal filaments, extend outward. These filaments include two cerci pointing to the sides and a single terminal filament pointing straight back.
Locomotion and Preferred Habitat
Without wings, silverfish move using their six legs in a quick, serpentine, or wriggling motion that resembles a fish swimming. This rapid movement is their primary method of escaping predators, and they are agile runners on horizontal surfaces. They are strictly nocturnal, using their speed and preference for darkness to avoid detection.
Silverfish thrive in dark, high-moisture environments, preferring a relative humidity level between 75% and 95%. They are often found indoors in basements, bathrooms, kitchens, and attics, where humidity is highest. Their diet centers on carbohydrates and proteins, specifically starches, which they digest using specialized enzymes. This dietary preference leads them to feed on household items like paper, book bindings, wallpaper glue, flour, and cereal.
Identifying Commonly Confused Winged Pests
The confusion about silverfish having wings often stems from misidentification with other small household insects. Earwigs, for example, are sometimes mistaken for silverfish due to their dark, flattened bodies. Earwigs do possess wings, although they rarely fly. Unlike the three caudal filaments of the silverfish, earwigs are easily identified by the two hard, pincer-like appendages, called cerci, extending from their rear.
Another common confusion is with firebrats, which are closely related and share the same wingless, three-tailed body shape. Firebrats lack the silvery sheen and display a mottled, grayish-brown color, preferring much higher temperatures, such as those near furnaces or boilers. Booklice are also small, sometimes wingless insects, but they are generally smaller than silverfish and lack the distinct three long caudal filaments.