Today we have a little insect I collected in the wilds of my own bathroom. Silverfish belong to the order Thysanura, or “fringe tail”, which takes its name from the three caudal filaments which fan out from the abdomen. (This is distinct from members of Archaeognatha, which have three caudal filaments that extend in parallel from the abdomen.) Silverfish enjoy cool, damp enviroments and starchy foods, making them common pests in bathrooms, basements and libraries. Although they do not bite or sting, they may do minor damage by nibbling on paper products, the glue of book bindings and wallpaper, and the starch in cotton or rayon fabrics. Outside of human homes they generally live in dead wood or leaf litter and eat lichens.
Head on view of a silverfish's small lateral eyes and three caudal filaments.
These little critters are impressively hardy: When I taught the introductory entomology lab a few semester ago I found a live silverfish living in a vial in the student collection.* The little silverfish had evidently been turned in several months before and had been surviving by devouring its own ID label.
The caudal filaments of silverfish are delicate and break easily.
*This is just one of many exciting and novel encounters I have had while overseeing student insect collections. One collection box I graded had a live wasp in a jar.
See also: Fire ant symbiotes: Nicoletiid silverfish
An ectosymbiotic nicoletiid silverfish with fire ant host species.
The small, pale insect in the midst of the fire ants above is a myrmecophilous (“ant-loving”) silverfish, a member of the order Thysanura and the family Nicoletiidae. This species of silverfish is one of a small but diverse group of insects and other arthropods that have adapted to living as symbiotes within an ant colony. Although these insects appear very different to human eyes, they coat themselves in chemicals which fool ants senses of smell and taste into believing them to be nestmates. Species of myrmecophilous silverfish have been known to groom their ant hosts, and feed on stolen prey or regurgitated food from the ants.
Most people are more familiar with silverfish as the small, silvery insects which frequently inhabit bathrooms or basements in human households. Silverfish are a primitively wingless species of insect (branching off from other insects prior to the evolution of wings). Thysanura means “fringe tail” and refers to the three caudal filaments extending in a fringe from the end of their abdomens. Nicoletiids are generally extremely small and pale, as well as completely eyeless.
A myrmecophilous nicoletiid silverfish from a fire ant nest.