You can discover orders of insects without leaving your house

16 Feb, 2026

Hang on let me adjust the cables at the back of the computer. A place left largely undisturbed by humans for quite some time.

Woah what is that insect crawling around on the floor?

So interesting. Immediately you might be thinking, 'what sort of weirdly odd numbered, 5 antennae insect is this?' But don't fret.¹²

You have help and yes it is another key.

This invertebrate key by the CSIRO is a really great resource. You should try it out. I mean it. This is a super-easy key, anyone can use it. Try it out, the image above is all you need.

For those that have attempted this at home, I will now continue on...

This is a species in the order of Zygentoma, more commonly known as silverfish. Note the key is now outdated using the previous term of 'Thysanura'. The individual in question may be in the genus of Ctenolepisma. Ctenolepisma have a worldwide distribution, found in warm regions across Africa, Asia, Europe, the Americas, the Middle East, even the Caribbean. The only exception is Australia. A revision of the genus Ctenolepisma noted Australia was the only continent where they exist from introduced domestic populations.

What even is a 'silverfish'?

They can be most easily distinguished by their three long, tail filaments, called cerci extending from their last segment. The cerci are more or less of equal length, with two perpendicular and one parallel to the body. Not all silverfish have eyes, but I believe my one does. Next to the compound eyes are two long antennae. Their wingless body is covered in minute scales. This gives them a gray or silver hue. Compounded with their movement being described as 'fishlike', the term 'silverfish' starts to make more sense.

They are one of the most primitive lineages of insects, having gone its own way, diverging before the evolution of winged insects in the carboniferous (358 - 298 Ma). Silverfish body design has remained more or less the same for the past 300 million years. So I mean it must be working alright for them.

So where do you look?

Look in the undisturbed areas of your home; unused drawers, old cupboards, under appliances. They feed on paper, cereals and starch. Anywhere there is paper is good. Bookshelves, old filing cabinets etc.. They prefer dark areas and will move away from the light.

They are not the only insects well adjusted to living in undisturbed, dark corners of our homes. It may even be possible some silverfish are predated by Daddy Long Legs Pholcus phalangioides.

This one is definitely living life on the edge.

Nearby another insect didn't get so lucky.

The need for a name

I don't want to give the impression you only find silverfish in houses. There are many more free-living silverfish species out there than indoor domestic ones! Some are known to be associated with termites and ants. Unfortunately a lot is unknown about the natural habitats of silverfish as the domestic, synanthropic ones have captured most attention and research. So much so, that the term 'Silverfish' has been reserved for these few household species, or even only to one species, Lepisma saccharinum. But personally, I use the term 'silverfish' liberally and broadly to include all species in the order Zygentoma.

What I find so insane, is that you might have seen a silverfish before, but you either; a) just didn't notice or b) didn't know what they were or what to call them. Because there was no specific name for you to use to label it, your memory remembers it more broadly as a 'bug', and moves on. Consequently, you may simply forget this whole interaction depending on how significant that moment was for you. Zygentoma is an order of insect with 550ish species. It deserves a common name.³ The fact we don't have a common name shows how understudied Zygentoma is.

Appreciation for useful old websites

I must stress strongly how cool it is to find old sites like the CSIRO invertebrate key. There are many things I like about it:

• Studying insects can seem daunting due to the immense diversity of species and their morphology. This basic key with no technical jargon is useful, and can distinguish between major groups. I appreciate it for that. Quickly you are directed to whole orders of insects you may have otherwise had no idea about.

• The fact you can download the key (top right of the starting page). Downloading this key also hinted at the date when this webpage was published, with the HTML document dated 28th April 2004. That's nearly 22 years old!!

• Also when you click on the 'invertebrates home' link above download button, it takes you to a strange webpage, saying the url is functional, something I don't understand the reason for, but I like it.

I always wondered if the fact these old websites still exist to present day makes its more or less likely to exist in the future? I worry that CSIRO will do some overhaul of the website, a new person will come in and say 'we need to remove all these old depreciated webpages'. Then the invertebrate key that I cherish is gone forever.

Then again maybe it's been so long now, that the page has been forgotten about? Is this possible? Fairly big organisations like the CSIRO must have accumulated so much data over the years and may lose track of where everything is?

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Footnotes