Top Five Insects I’ve Seen – #4 – The Rose Chafer (Cetonia aurata)

Surely one of the most stunning insect species we have in the UK – the rose chafer beetle (Cetonia aurata) (Credit: Me)

I was initially going to write a list of top five most striking UK insects but alas when I actually put grey matter to the task I realised the list would be mostly, if not exclusively, beetles.

Beetles, the order coleoptera, are a huge group. Of all the species described in the world somewhere around 40% of them are beetles and there are around 400,000-500,000 species of them! Little wonder, then, that they vary from tiny barely perceptible grey things to the most beautifully coloured little living gems and jewels on our planet.

The UK alone contains over 4,000 species of beetle.

This beetle display in the Horniman Museum, London is only a fraction of the wealth of diversity the beetle has evolved. (Credit: Me)

So what makes a beetle?

Well the simple rule of thumb is that beetles will have a particularly hardened exoskeleton. Where they are flyers they have hardened wing cases, called ‘elytra’, that will cover their wings when not flying but are usually not used for flight. There are other specifics to do with mouthparts, leg segments, and antennae segments but welcome to the world of insect identification and classification! It’s hard work as I know from scrabbling for IDs for the things I spot!

A rose chafer in Germany preparing for take-off! Notice the wings protruding from underneath the shimmering green wing casings (elytra) that are a trademark for identifying flying beetles. Some species fly with these elytra out, others, like the rose chafer, fold them back in during flight. (Credit: Bluecloud CC-BY-SA-4.0)

Of course this is biology. There are wingless beetles, water beetles, ground beetles. The evolutionary biologist J. B. S. Haldane once famously quipped when asked about the intentions of the mind of God that He has “an inordinate fondness for beetles.” And whatever your thoughts on God, creation and evolution the overwhelming successes of the adaptation of the beetle form are inarguable, and clearly favoured by nature!

So what’s so special about the rose chafer? Look at it. This is not some picture-book fairy-tale made up creature. It’s not some exotic species from the rainforests of the Congo in Africa or the Amazon in South America. This is not some pretty little artefact from ancient Egypt once worn as a brooch. This is a UK native beetle that is otherworldly beautiful.

We have many beautiful beetles in the UK, the Green tiger, the rainbow leaf beetle, the wasp beetle – and many more. I have seen a few of them and none of them gave me that same ‘wow!’ as seeing my first rose chafer.

I’ve recently written an article about human bias in conservation. I will confess my regard for this beetle is evidence of those biases in me. I am swayed by this insect’s beauty. In fact many of the species on this list are on this list because their appearance gives me immediate positive chills. These biases are innate and we must work to overcome them, and there are many dull species I enjoy because of what they are, what they do, and the unique beauties they possess.

One thing I’ve noticed with beetles is they’re very often doing it! To the extent that I have been described by friends as a beetle pornographer because of the amount of photos I have of beetles going at it. (Credit: Rollstein via Pixabay)

But a big, stunning insect is always going to be that immediately available draw. It’s always going to go straight from your eyes to your heart. Given my intention is to try to engage people who may not like insects I figured I’d start with beautiful beetles!

Rose chafers are a member of the scarabaeidae – scarab beetles. Perhaps the lingering Primary School teachings on ancient Egypt also colour my perception of this beetle, giving it a reverence since it looks so much like it belongs shrouded in ancient mystery and written in hieroglyphs.

Warning: Technical language!

The incredible colour, that metallic green oil-slick iridescence, is a form of ‘structural colour’. That is to say it is not like your hair colour or eye colour which is determined by pigments – colouring substances that work by selective absorption of different wavelengths of light. Rather the colour of the rose chafer is created mostly by the way the exoskeleton, the insect’s hard shell, is grown. It forms crystals of chitin (what insect shells are mostly made of – it’s a polysaccharide, a long-string of modified glucose molecules – a sort of sugar-cement!) and other proteins which ‘polarise’ the light – effectively changing the way the light travels and thus how it hits your eye.

This green, shimmering oil-slick appearance is not the result of pigments, like your hair colour. Rather tiny structures within the shell itself manipulate light (in this case exhibiting ‘left circular polarisation’) which interferes with the light waves and thus, how you see them. Structural colour is common in nature. By looking at the beetle through a right circular polarised lens it appears colourless! (Credit: orientalizing CC-BY-NC-ND-2.0)

Sorry, it’s all very technical! But basically light hit stuff, make light move funny, look pretty to eyes!

The rose chafer is more than just beautiful, though. Its larval stage (which is generically grubby in appearance, a yellow-white grub with a little orange head) is saprophagous – it is a detritivore – put simply they eat dead stuff! Rotten plant matter, mostly. This is important for the cycle of nutrients and for soil health. The adults tend to eat pollen and nectar and sometimes the flowers themselves and, given their name, have a fondness for roses. This does suggest they offer pollination services but they can also leave holes in your flowers from having a nibble!

One of the things I think people forget when thinking about insects is their life cycle. Some insects spend the bulk of their lives in a larval stage and yet we most associate that insect with their brief-lived adult form.

A rose chafer adult (left) and larva (right) (Credit: Daniel Zippert CC-BY-SA-4.0)

The metamorphoses, the transformations they can undergo are so drastic we often think of them almost as separate species. So it can be difficult to see a beautiful white butterfly flittering above your garden and associate it with those caterpillars that keep gobbling up your cabbages. They are the same animal, though!

Rose chafers are active generally from around May to late-September/October and we are actually approaching in the peak of their activity in June and July. They are mostly a southern species here in the UK, distributed quite widely there, with only sporadic sightings further north than the midlands. Naturally, given the name, keep an eye out for them on roses, particularly the dog rose.

I have had great success finding rose chafers on these umbellifer flowers, too. And, as you can see, they are a haven of all sorts of insect biodiversity! (Credit: Me)

So get out there and see if you can spot this fantastic species and behold the jewelled brilliance yourself.

If you wish to get more involved or learn my about insects and invertebrates here are some links to The Royal Entomological Society and Insect Week resources.

Royal Entomological Society Website
Twitter
Facebook
Instagram

Insect Week Website
Twitter
Facebook
Instagram

Or you can read some of my other articles about insects and invertebrates below.

My Top Five UK Insects I’ve Seen: Introduction
An introduction to my top five insects, and a short look at why we need to see our insects differently.
Top Five Insects #5 – The Tawny Mining Bee (Andrena fulva)
Under-appreciated spring bee with a female who has incredible fox-red fur.

Top Five Insects #3 – The Cinnabar Moth (Tyria jacobaeae)
Proof that moths can be as amazing as butterflies, with a lovely caterpillar!
Top Five Insects #2 – The Thick-Legged Flower Beetle (Oedemera nobilis)
A charming iridescent green flower beetle, some of whom have thick thighs!
Top Five Insects #1 – The Ruby-Tailed Wasps (Chrysis sp. or Family Chrysididae)
Stunning little jewels that can teach us much about the diversity of wasps and insects.

Top Ten Hated (But Misunderstood) Animals – #1 – Wasps
A look at wasps in all their diverse beauty and glory and why they are important to us. A long-read.

The Wasp Tragedy – How Can We Help?
A few tips on how you can encourage wasps and other insect and invertebrate biodiversity in your home or garden.

Insects: The Savage Eden Before Your Eyes
A more in-depth look at my journey as I developed a relationship with insects and their role in our ecosystems.

Grown-Ups Guides: Hedge-Hunting for Bugs!
A short guide on how a total novice can get started appreciating the tiny wildlife in the undergrowth (safely)! Aimed at adults.

Human Bias and Animal Myth in Conservation
Not insect-specific but hugely relevant. Adapted from a twitter thread looking at how humans form ideas and relationships with the natural world.

Published by Karl Anthony Mercer

Karl Anthony Mercer is a writer, poet, author, musician and part-time dandy. He can often be found squatting in fields looking at insects (he is an unapologetic wasp fanatic), wandering around museums over-dressed, or hiding in a dank corner singing sad songs on a small guitar. His writing on WordPress consists of MercersPoems - an outlet for his poetry often using natural imagery, gothicism and decadence to explore the struggles of living as an autistic person; and We Lack Discipline - Where he writes about factual, often academic topics he has learned and is interested in (e.g. biology, psychology, Roman history etc.) with an inimitable, often light-hearted and irreverant style. You can support Karl by; Subscribing to the We Lack Discipline Patreon - https://www.patreon.com/WeLackDiscipline Or buying him a coffee (he loves coffee!) - https://ko-fi.com/welackdiscipline

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