Silverfish

The silverfish, Lepisma saccharinum, is a primitive wingless insect in the order Zygentoma (historically Thysanura), a lineage that diverged very early from other insects and retains many ancestral features. Fossil relatives of this group date back hundreds of millions of years, making silverfish one of the more evolutionarily ancient insect forms still living today.

This species is notable for its distinctive metallic, scaled body that gives it a fish-like sheen and its rapid, wriggling locomotion, which it uses to dart for cover when exposed to light. Unlike most insects, silverfish continue to molt throughout their adult lives.

Silverfish play a minor decomposer role, feeding on starches and organic debris, and their ancient body plan makes them of particular interest to entomologists studying early insect evolution.

• Elongated, teardrop-shaped body tapering from a wider head/thorax region to a narrow abdomen.
• Covered in fine, silvery-gray scales that give a metallic sheen.
• Three long, slender tail filaments (cerci and a central appendage) extending from the rear.
• Long, thin antennae and no wings at any life stage.
• Lookalikes: firebrats look similar but have a mottled gray-brown pattern and prefer warmer, drier locations near heat sources rather than damp areas.

Silverfish are found worldwide in a variety of climates, typically indoors in dark, humid microhabitats such as basements, bathrooms, closets, and areas behind wallpaper or stored boxes. They are nocturnal and avoid light, remaining hidden during the day and emerging at night to forage.

Silverfish move with a distinctive fish-like wriggle and can run very quickly when disturbed or exposed to light. They feed on carbohydrates and starches, including paper, glue, and dry organic matter, acting as minor decomposers within indoor environments. They are solitary and largely nocturnal, avoiding open, well-lit spaces.

Silverfish undergo gradual, ametabolous development, meaning young nymphs hatch from eggs looking like tiny replicas of adults and simply grow larger with each molt, without a pupal stage. Females lay small clusters of eggs in hidden crevices, and nymphs take several months to over a year to mature, continuing to molt periodically even as adults. Under favorable humid conditions, silverfish can live for several years.