About 6 months ago I noticed a new friend in my apartment. It lived in my bathroom and only came out during the night (not sure how it knows when it is nighttime if there are no windows in the bathroom). I called him Jimmy. Seems harmless. About 8mm in length. Moves fast but is not running away scared. It has now moved to the kitchen. I think it has 6 legs, antennae and a weird double tail.

Here are pictures, low quality because it is tiny and my phone camera is not so good.

enter image description here

enter image description here

I live in Ireland.

  • 7
    The fact that you think it has moved to the kitchen is a sign that you have many many of these living in your apartment. They will happily snack on any paper (books, photos etc), rice, bread, wallpaper, carpets, clothing, silk that you have lying around. In other words, they are considered a pest, so you will probably need to get some ways of removing them from your apartment.
    – bob1
    Commented Jul 19, 2020 at 22:20
  • 4
    @bob1 Remove them? Why? I can stop cleaning the floor. There is such food left over there I can feed hundreds of them. They can eat the books too, I don't read them.
    – Dharman
    Commented Jul 19, 2020 at 22:21
  • 8
    Your neighbours / landowner / residental community / etc. might not share your views and could potentially be quite upset when they trace back the source of the infestation in their apartments to yours and find out about your attitude. There might even be a legal code for such occasions, better check on this now than get burned later.
    – zovits
    Commented Jul 20, 2020 at 8:13
  • 14
    As pests go, they're not particularly harmful (although I still wouldn't deliberately encourage an infestation). The real concern is that the same moist conditions which they thrive in are also good for the growth of fungi such as toxic black mold. If you see a lot of silverfish in your house, you might have a problem lurking in your walls. Commented Jul 20, 2020 at 9:13
  • 6
    I wonder if outdoors.SE is the right forum for this question. In my experience, silverfish seem to exclusively be encountered indoors. Commented Jul 20, 2020 at 17:44

2 Answers 2


This is, I believe, a silverfish.

This is the picture from the Wikipedia article;

enter image description here

A silverfish (Lepisma saccharina) is a small, primitive, wingless insect in the order Zygentoma (formerly Thysanura). Its common name derives from the animal's silvery light grey colour, combined with the fish-like appearance of its movements. The scientific name (L. saccharina) indicates that the silverfish's diet consists of carbohydrates such as sugar or starches.

They’ve always appeared for me in warm and damp places like the bathroom and indeed, this is confirmed in the Wikipedia article:

They inhabit moist areas, requiring a relative humidity between 75% and 95%. In urban areas, they can be found in attics, basements, bathtubs, sinks, kitchens, old books, classrooms, and showers.

  • Yes, the Wikipedia article describes it exactly and the image matches.
    – Dharman
    Commented Jul 19, 2020 at 21:44
  • I once saw one in a hands-off server room, under the raised floor. Commented Jul 21, 2020 at 7:57
  • 1
    They are insects if you use the loose definition of the word, i.e. including "primitive insects". They are not true insects because they don't have wings. However, they are very closely related, being more closely related to true insects than to any other major group such as arachnids (spiders, scorpions, ticks, mites, etc.).
    – CJ Dennis
    Commented Jul 23, 2020 at 1:39

I just wanted to say that they are not considered a pest as some comments are telling you, they are considered beneficial. From the German Wikipedia article roughly translated: "Silverfish in low numbers are harmless. In fact they are beneficial because they eat mold. High numbers of them is usually a sign of a big mold infestation."

I myself sometimes see one or two silverfishes in my bathroom and I've seen silverfishes there (mostly at night or early morning) for at least 5 years and haven't had any problems. So I wouldn't bother throwing them out if there are only a couple.

  • 6
    they are considered beneficial Really? "Silverfish feed on starchy materials and items that are high in protein. They are active at night and cause damage to books, stored food, and clothing" Commented Jul 20, 2020 at 17:21
  • 3
    yes in german "Nützling" I'm not sure if beneficial is the right english term atleast thats the way google translates it. The english article seems to greatly exaggerate with regards to damage to books, stored food and clothing.Atleast in my experience I've never had any trouble with them.
    – ctsmd
    Commented Jul 20, 2020 at 17:29
  • 3
    @ctsmd: maybe because in Germany conditions that are good for silverfish are considered far too damp for books... (not sure whether such moisture can be avoided where books are stored in Ireland)
    – cbeleites
    Commented Jul 20, 2020 at 20:38
  • 3
    The number of books at my parents' house that have certain pages that can't be read anymore because of silverfish! They're not harmless and shouldn't be encouraged.
    – CJ Dennis
    Commented Jul 21, 2020 at 3:45
  • 10
    There is a difference between the regular 'Silverfish' (Lepisma saccharina), which is ok, and the 'long tail silverfish' (Ctenolepisma longicaudata)) which is a disaster as that eats all paper etc. and is really annoying Commented Jul 21, 2020 at 6:54

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