These insects belong to the order Zygentoma, what should be found on the last page of a dictionary (the last word is Zyzzyva, a genus of weevils from Africa). The family Lepismatidae contains about 190 species of silverfishes. Not sure how many of these species live in our bathrooms.
What we know is that case 3704 contains opinion 2427 with the result that the silverfishes are considered neuter and not feminine. This reflects in the ending of the specific epithet is an -um, not an -a. And it shows that the work of the International Commission on Zoological Nomenclature somehow is a very bureaucratic one.
Silverfishes are surprisingly interesting to read about, they are also somehow living fossils. They are considered one of the most primitive insects, means they haven’t changed much since they appeared. Unbelievable 480.000.000 years ago insects have most probably developed from crustaceans. They were already close silverfish ancestors! Only 80 million years later the first insects developed wings, but the silverfishes made it without wings till today. Thinking about it, there are not so many insects without, beetles, ants, flies, locusts, all have wings at some stage.
They feed on everything you can find in a bathroom, including cellulose, which is found in paper and many glues. This is by the way of high interest for researchers. Breaking down cellulose to its monomer, sugar, is a challenging task. It would enable us to make fuel from non-edible crops. Making bio-ethanol from sugar though is easy since we do that for thousands of years (skol!). Silverfishes together with termites, and some roaches and beetles, are investigated as solution for the breakdown of cellulose. There are lots of paper based papers about this topic.
I “identified” my silverfish based on the picture hier, and somehow its common name Paper silverfish totally fits to the story! The color is darker compared to Lepisma saccharinum, and it seems to be more hairy. Though as always this ID is not 100%.
Last but not least silverfishes are a welcome snack for our cat, and they seem to be more tasty than jumping spiders.
Deutsch 
English