Ancient insects

Funnily enough, today in my house I came across two of these insects, called Silverfish (order Thysanura), in separate rooms. They quite often occur in human habitations, though I've never seen them before in mine. Was it just a coincidence that I saw my first and second on the same day, or am I witnessing the overrunning of the whole house?

These insects, together with the similar looking bristletails (Archaeognatha), are generally thought of as 'primitive' insects. Looking at the phylogeny of insects (e.g. here at tolweb.org) it's obvious that the two groups branched off quite early from the rest of the insects. Silverfish and bristletails were originally collectively called the 'Apterygota' (without wings), though this grouping is now considered artificial in the sense that the two orders diverged separately, so do not constitute a clade.

So they're thought to have characters pretty similar to whatever the ancestral insect was. And they seem to survive pretty well by sticking to their guns, dated as they are.

They can eat almost anything, and this keeps them happy places we might think are pretty nutrient poor. Take human houses, libraries, museums; silverfish happily eat book binding glue, paper, photos, fabrics (natural and synthetic)... nothing I'd enjoy munching on.

I sort invertebrate pitfall trap contents brought back from the Simpson Desert, a fairly inhospitable part of the earth. Thysanura turn up regularly in the samples; they obviously don't mind the hot, dry conditions where nutrients aren't a thing to waste.

So I won't be too worried if these things have taken a hold in my house. Hopefully they won't eat through all my books. Moreover, it's fun to see something that looks like it just crawled out of the ocean living happily in our world of processed and synthetic materials.

Further Reading:
Wikipedia: Silverfish
Wikipedia: Insect Evolution