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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.

Freiheit
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Dharman
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    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 Jul 19 '20 at 22:20
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    @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 Jul 19 '20 at 22:21
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    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 Jul 20 '20 at 08:13
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    @bob1 I’ve never seen more than one at a time and never heard of the potential for infestation. I didn’t know until I posted my answer that they can cause damage. – Darren Jul 20 '20 at 08:47
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    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. – Ilmari Karonen Jul 20 '20 at 09:13
  • Are you sure it only comes out at night? – gerrit Jul 20 '20 at 12:10
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    I wonder if outdoors.SE is the right forum for this question. In my experience, silverfish seem to exclusively be encountered indoors. – Digital Trauma Jul 20 '20 at 17:44
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    @DigitalTrauma - you just aren't looking in the right places to see them outside. They existed before we had houses: link – bob1 Jul 21 '20 at 00:45
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    @Dharman : you might not care about books, but what about wallpaper, carpet, clothes? And what about more harmful pests which will thrive if you leave out food for the silverfish? – vsz Jul 21 '20 at 04:33
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    bob1: As pointed out in comments elsewhere, there is a difference between silverfish (Lepisma saccharina) and the long-tailed silverfish AKA gray silverfish AKA paper silverfish (Ctenolepisma longicaudata). "In recent years, gray silverfish have increasingly become an – Peter Mortensen Jul 21 '20 at 15:12
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    'cont - issue in indoor environments in Europe, especially in newly built houses with a stable climate beneficial for the growth and reproduction of this species. As a food generalist with the ability to digest the cellulose contained in paper and cellulose-based textiles like rayon, Ctenolepisma longicaudata is considered a pest species in cultural heritage institutions like libraries and archives." – Peter Mortensen Jul 21 '20 at 15:13
  • It amazes and amuses me that these are "new" to you btw. Like asking about a rat or a pigeon. :) – pipe Jul 21 '20 at 17:04
  • @pipe People live in various parts of the world. What is common for you can be a novelty for me. There's very little insects in the country where I live. For me seeing a bug is something worth my attention, it's not every day that I can see one. – Dharman Jul 21 '20 at 17:06

2 Answers2

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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.

Darren
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  • Yes, the Wikipedia article describes it exactly and the image matches. – Dharman Jul 19 '20 at 21:44
  • I once saw one in a hands-off server room, under the raised floor. – David Tonhofer Jul 21 '20 at 07:57
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    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 Jul 23 '20 at 01:39
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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.

Peter Mortensen
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ctsmd
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    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" – Binary Worrier Jul 20 '20 at 17:21
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    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 Jul 20 '20 at 17:29
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    @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 unhappy with SX Jul 20 '20 at 20:38
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    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 Jul 21 '20 at 03:45
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    @cbeleitesunhappywithSX yes you might be right. I live in an apartment without any mold or problems with moisture so that's probably why I only see them in the bathroom or sometimes in the kitchen sink. Maybe if you have an attic which is hard to maintain/keep moisture out, then I can imagine them being able to survive there aswell and being a problem for things stored there if they eat them. But they should be no problem in a compact easy to maintain home. – ctsmd Jul 21 '20 at 06:22
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    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 – Rob Audenaerde Jul 21 '20 at 06:54
  • @RobAu: Looked up the long tail one - the German name translates to (little) paper fish so that seems indicative. The German Wiki page lists a "first sighting in Germany" in 2007, but says they are invasive and need less moisture than silverfish. So maybe we really don't have them (yet). I also wouldn't expect silverfish in the attic here: it's is either hot & too dry or too cold. – cbeleites unhappy with SX Jul 21 '20 at 10:39
  • @cbeleitesunhappywithSX yes in Dutch it is "Paperfish" as well. And they are considered a pests here, especially in new-built homes which are dry (which paperfish prefer, instead of silverfish, which prefer more moldy) – Rob Audenaerde Jul 21 '20 at 10:56
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    BTW: I believe OP has a regular silverfish, based on the smooth looking back. – Rob Audenaerde Jul 21 '20 at 10:59
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    This really is a confusion of very different species (or even genera) the invasive Ctenolepisma longicaudata is spreading from the Western Europe and is probably not too common in some eastern parts of Germany. map The chaotic English biologic nomenclature does not help too much to avoid the confusion. – Vladimir F Героям слава Jul 21 '20 at 11:37