Silverfish Lepisma saccharina
Silverfish belong to a small order of insects, represented by less than 600 species world wide. Many scientists think Silverfish are not even insects, but a group of 6-legged animals on their own, besides the insects and the springtails. As this discussion has not been closed yet, we won't go into all the details. We use the classic approach: Silverfish, Springtails and Bristletails all belong to one group of very primitive insects.
The Silverfish is a small species, measuring up to 12 mm. It is a wingless animal, in possession of two antennae and three wires at the back. It has a blueish silvry colour. It rather moves like a fish in the water, making the scales reflect the light in much the same way the scales of silvry fish do. That is why they are called Silverfish. In cooler parts of the world the Silverfish is exclusively encountered indoors. It prefers rather cool and moist conditions. Thus it is usually seen in cellars, attics, bathrooms and so on. They are common in houses. One might even say that every house has some. But they are nocturnal, shy and don't show themselves very often. Reproduction is rather uncommon. The male just drops his sperm in a good spot and the female just picks it up. The Silverfish moulds all his life, even once adult. And they are long-lived: up to 4 years! Males, females and young are identical.
Indoors only three species of Silverfish are found. The real Silverfish which prefers dark, moist and cool places. Its cousin, the Gray Silverfish, prefers dark, warmer and dryer places. It looks like the common Silverfish very much, but it has much longer wires on the rear end. It is often found in dry attics and bookshelves. It feeds on paper and can do some dasmage to books. The third species is the Firebrat, which is not only smaller, but brownish as well. It can only survive in high temperatures and used to be common in blacksmith's shops, bakeries etc. It is much rarer nowadays. These species are found all over the world. Two more species are common in Northern America and in Australia yet another species is found.