Silverfish

Lepisma saccharinum — the silverfish — is one of the most ancient surviving insect species, belonging to order Zygentoma which split off from the rest of the insect lineage approximately 400 million years ago, well before wings evolved. The body plan (elongated, flattened, three terminal filaments at the tail, scale-covered, fish-shaped silvery profile) has barely changed since the Devonian. The species is wingless and apterygote (a primitive 'before wings' lineage), capable of running rapidly with characteristic side-to-side fish-like motion. Silverfish are extraordinarily long-lived for small insects: females mature over 2-3 years and can live 8+ years total, far longer than most insects of similar body size. Reproduction is unique — a 'love dance' in which the male deposits a sperm packet (spermatophore) on the floor and then leads the female through a ritualized antenna-touching pattern that ends with her walking over the spermatophore and picking it up. Silverfish are detritivores in the wild but are common indoor pests because they feed on starches, sugars, paper, fabric, glue, dead insects, and dandruff — all materials abundant in human dwellings. They prefer high humidity and warm dark spaces (bathrooms, attics, basements, under sinks). The species is harmless to humans (no bite, no venom, no disease) but damages books, photographs, wallpaper, and stored fabrics.