Fishmoths
Fishmoths (Silverfish) – Lepisma saccharina
Commonly called “fishmoths” in South Africa and “silverfish” worldwide because of their shiny, metallic-silver or pearl-grey colour and the distinctive fish-like, wiggling movement they make when they run.
Appearance and biology
- Teardrop-shaped, flattened body that tapers from head to tail
- Length: 12–19 mm (adults)
- Covered in tiny silvery scales that rub off easily (if you squash one, you’ll see the silver scales stick to your finger)
- Three long, tail-like appendages (cerci) at the rear and two long antennae at the front
- Six legs and very fast, erratic movement – they can run up to 1 metre per second
- No wings at any life stage
- Extremely long-lived for an insect: adults can survive 3–8 years and can go without food for up to a year
Silverfish prefer dark, damp, warm places (25–30 °C and 75–95 % humidity). They are strictly nocturnal and shy away from light, which is why you usually only spot them when you suddenly switch on a light or move a box that hasn’t been touched in months.
Where they hide in your home
- Behind skirting boards, architraves, and cornices
- Inside and behind kitchen and bathroom cupboards
- Under sinks and around leaking pipes
- Behind picture frames, mirrors, and wall hangings
- Inside bookcases, between pages of seldom-used books, and in cardboard boxes
- Under carpets and rugs (especially in humid rooms)
- In linen cupboards, folded towels, bedding, and clothing storage
- Inside wall voids, roof spaces, and sub-floor areas
They often enter homes in second-hand furniture, old books, cardboard boxes, or even new gypsum board and wallpaper paste (which contains starch they love).
What they eat – and the damage they cause
Silverfish have chewing mouthparts and a digestive enzyme that breaks down starch and cellulose. They feed on:
- Paper, books, photographs, and wallpaper (especially the starch-based paste behind wallpaper)
- Natural fibres: cotton, linen, silk, wool, leather, and rayon
- Carpets, rugs, tapestries, and curtains made from natural materials
- Clothing – particularly suits, jerseys, and items stored long-term
- Food spillages: sugar, flour, pasta, dead insects, and even their own cast-off skins
- Glue in book bindings, cardboard, and packaging
Damage is usually irregular holes, surface grazing, and yellow staining. In heavy infestations they can completely destroy the nap of wool carpets, eat large sections out of silk ties or suits left in storage, ruin priceless books and documents, and turn stored linen into lace.
Signs of a fishmoth infestation
- Small irregular holes or scrape marks on clothing, paper, or carpet
- Yellowish stains on fabric or paper
- Tiny black pepper-like droppings
- Cast-off silvery skins in cupboards or behind furniture
- Seeing the insects themselves darting for cover when disturbed
Why they are difficult to get rid of
- They reproduce slowly (females lay only 1–3 eggs per day, up to 100 in a lifetime), but because adults live for years the population builds up steadily
- Eggs are tiny, white, and laid singly in cracks and crevices – almost impossible to find
- They avoid baits that work on cockroaches and ants
- They can survive extreme conditions and starvation
If you’re finding mysterious holes in your best suits, books with pages that look grazed, or little silver insects wriggling away when you open a cupboard, you have a fishmoth problem that won’t go away on its own.
Call SWAT Exterminators for a treatment programme that reaches the hidden places where fishmoths live and breed. Protect your wardrobe, your library, and your carpets – don’t let these ancient little scavengers eat away at your valuables.