The fastest useful split
Both have three tail filaments; temperature and body pattern are the simplest household separators.
Do not rely on a single color match. Start with scale and physical form, then check where the sign accumulates and whether a companion clue supports one candidate over the other.
| Feature | Silverfish | Firebrat |
|---|---|---|
| Body | Uniform silver | Mottled gray-brown |
| Temperature | Cool/moderate humid | Hot appliance/boiler |
| Damage | Paper/starch | Similar near heat |
| Movement | Fast/nocturnal | Fast/nocturnal |
Measure temperature where activity repeats.
Correct moisture and clutter first.
Open safety guidanceCheck each full evidence profile
Silverfish
Lepisma saccharinum
Silvery tapered body, three tail filaments and irregular surface grazing in cool humid paper or storage areas.
Firebrat
Thermobia domestica
Mottled tapered insect with three tail filaments recurring near a hot, humid appliance or boiler zone.
Why a visual match can fail
Scale can be distorted by a close-up photograph, loose material may be moved by cleaning or airflow, and old evidence can change color or texture. A reliable conclusion uses multiple observations that point in the same direction and preserves contradictory details instead of forcing a match.