eTawau > Insects of Borneo > Beetles > The jewel beetle with one wing

The jewel beetle with one wing

Tawau River, June 2011 — the most beautiful thing I have found on the ground, and it was on the ground for a reason

A Sunday afternoon in the abandoned oil palm beside the Tawau River, opposite Pasar Semarak. There was a beetle on the bare earth, about 25 millimetres long, and it was not going anywhere.

I picked it up. On my thumb it lifted its wing case, opened its wing and beat it — and stayed exactly where it was. It did not bite me. And then I saw why it could not leave.

One wing case, raised. On the other side of this beetle there is nothing at all — no wing case and no wing. That is why the blue-green abdomen is showing along its whole length instead of being tucked away out of sight.

What a jewel beetle is

This is a jewel beetle — family Buprestidae — and they are one of the great sights of a Bornean afternoon. There are about 15,500 species of them in the world, in 775 genera, and the tropics have the best of them.

The grubs are called flat-headed borers. They tunnel through wood — roots, stems, fallen logs — usually wood that is dying or already dead, and they may take years to do it. The adults come out into hot sunshine, and that is when you meet them.

The same beetle head-on: a broad flattened face with a pale grey powdery central area between two large dark curved eyes, short black saw-toothed antennae held forward and down, and stout dark legs braced on the pink skin of a thumb. — **How to know one.** Short **saw-toothed antennae** — each segment drawn out into a triangular tooth. Big eyes down the sides of the head. The head sunk back into the front of the body with no neck showing, and the whole animal compact and boat-shaped. No labels on this one: this is what it actually looks like.

Why the colour is not paint

Look at that abdomen again. Blue where the light strikes one way, green where it strikes another, and it never fades — a jewel beetle in a museum drawer a hundred years old is still that colour.

That is because there is no pigment in it. The colour is structural: the surface of the shell is built in microscopic layers, and those layers reflect some wavelengths of light and cancel others. It is the same trick as a soap bubble or an oil film on a puddle. Nothing can bleach it, because there is no dye to bleach — you would have to destroy the shell itself.

And that is why this beetle is still spectacular although it is broken. It has lost half its flight equipment, it is at the end of whatever life it had, and it is still one of the most beautiful objects you will find on the ground in Tawau. The colour does not know anything is wrong.

Why it could not fly

Here is the answer, and it took me a moment to see it even with the beetle in my hand.

The whole left side of its flight equipment was gone. Not just the wing — the wing case as well. Both of them, together, off the same side.

The same beetle from above on a thumb, its brilliant blue-green segmented abdomen fully exposed. One membranous hindwing is extended to the right; the left side of the abdomen is completely bare with no wing case beside it. Labels mark the one remaining hindwing, the absent wing case on the left side, and the abdomen bare to the tip. — **Seen from above, the asymmetry is the whole story.** On the right, a wing case and a hindwing. On the left, the edge of the abdomen runs bare from the thorax to the tip, with nothing lying over it and nothing standing beside it.

A beetle flies on its hindwings — the thin folding membranes. The wing cases are the hard covers: modified front wings that fold down over the membranes like a lid and protect them, and which must be lifted out of the way before the beetle can fly at all. Take one whole side away and two things follow at once:

It cannot fly. One hindwing cannot lift a beetle, and it cannot balance one either. All it can produce is a lopsided push.
It cannot protect itself. The soft top of the abdomen is meant to be under a lid. On this beetle half of it is permanently in the open — which is why you can see that astonishing blue and green at all. You are looking at something you are not supposed to be able to see.

A photograph is not the whole observation. I knew about the missing side because the animal was in my hand and I could look at it from every angle. In the pictures it is there — but it is the sort of thing you see only once you know to look for it, because what your eye notices first is the colour. When you write up a record, write down what you saw with your own eyes, not only what the camera caught. They are not the same thing, and the eye was there first.

What could take a whole side off a beetle

Honestly: I do not know, and the photographs cannot tell you.

A bird or a lizard that grabs a beetle side-on and loses its grip could strip a wing case and a wing together — they come off the same shoulder. So could a mantis, or a bigger beetle in a fight over a feeding place. It might also have gone wrong at emergence: a beetle that cannot get clear of its pupal chamber properly comes out damaged and stays that way for life, because an insect that has finished growing never repairs anything. There is no healing and no regrowth. Whatever happened had already happened for good.

What I can say is that it was alive, alert, and still trying, on bare earth in the sun, on a Sunday afternoon in June.

Why it still has no name

The family is certain. Beyond that I have stopped, and the reason is worth explaining because it is a lesson for anybody photographing beetles.

For jewel beetles, almost everything that separates one genus from another sits on the closed upper surface — the colour and pattern of the wing cases when they are shut down over the back, the sculpture of the prothorax seen from directly above, the shape of the wing-case tips. That is the one photograph I do not have. In all three of my frames the beetle is open, because it was trying to fly the whole time.

And there is a sadder version of the same problem: this beetle could never have given me that photograph anyway. An animal missing one wing case cannot close up into the ordinary shape. Whatever it was, it stopped being able to show it long before I found it.

So the record stops at Buprestidae, and it is posted on iNaturalist where people who work on this family can look at it. Names that get suggested for big metallic South-East Asian jewel beetles include Chrysochroa, Chrysodema, Catoxantha, Megaloxantha, Belionota and Cyphogastra. I am not going to choose one from a photograph of an open beetle. A guess with a Latin name on it is still a guess, and it is harder to undo than an honest blank.

If you find a jewel beetle — the photograph to take

Straight down on the back, wing cases closed. This is the one that matters. Wait for the beetle to settle if you can.
A ruler, a coin, or a fingertip in the frame for scale.
Then the side view and the head-on view, which are the ones everybody takes first.
Write down the plant or the log it was on. The grubs live in wood, so what the adult is sitting on is often a clue nobody else recorded.

The record

26 June 2011 · 4:24 pm · Tawau River, opposite Pasar Semarak

On bare ground in the abandoned oil palm

The Tawau River Triangle — the abandoned oil palm beside the Tawau River, opposite Pasar Semarak, at Km 7 of Jalan Kuhara, about 7 km from Tawau town. One jewel beetle (Buprestidae), about 25 mm, alone, on bare earth and unable to fly — the left wing case and left hindwing both missing. Blackish wing case with fine lengthwise ridges; abdomen brilliant metallic blue and green with serrated side margins; a bright red patch at each corner of the prothorax and a metallic green line along its front edge. Lifted onto a thumb for the photographs, which is the background you see, and left where it was found.
Three frames at 16:22:55, 16:24:03 and 16:24:10.
— iNaturalist observation 400043427

This is the fourth record on this site from that one kilometre of riverside, and the reason it exists is uncomfortable: I could photograph this beetle because it was broken. A whole one would have been gone before the camera was up. That is true of a great deal of what gets recorded anywhere — the sick, the old, the damaged, the ones that came to a lamp at night. It does not make the record less real. It does mean a list built from records like this one is always a little tilted towards the unlucky, and it is worth saying so.

Please do not collect them. Jewel beetles are taken in large numbers for the specimen trade, and their wing cases have been used as ornament — sewn into embroidery, set into jewellery — for centuries, precisely because that structural colour never fades. A photograph lasts just as long and costs the animal nothing. If you find one alive, photograph it and let it go on. If you find a dead one, the wing cases on the ground are worth looking at with a lens: they are still the same colour, and they always will be.

Words you may meet

Buprestidae: The jewel beetles: a family of about 15,500 species, most of them metallic, whose larvae bore in wood.
Elytron (plural elytra): A wing case — the hardened front wing of a beetle, which folds down as a lid over the flying wing beneath. This beetle has one.
Hindwing: The thin folding membrane a beetle actually flies on, kept under the wing case.
Flat-headed borer: The larva of a jewel beetle, named for its broad flattened front end, which tunnels in wood.
Structural colour: Colour produced by microscopic layers in a surface reflecting and cancelling particular wavelengths, rather than by any pigment. It does not fade.
Serrate: Saw-toothed. Used here of the antennae, and of the side margins of the abdomen.
Prothorax: The front section of a beetle's body, between the head and the wing cases.

Tawau River Triangle — the abandoned plantation by the Tawau River — the place, its history, and the other records made there
The trilobite beetle — another beetle from the same ground, filed under no wings because the female never grows any
The Three-horned Rhinoceros Beetle — the other big beetle on this site, and the other one that could not get off the ground
Beetles
The green queen and the maggots · A white mealybug on a grass blade — the other two records from this riverside
Insects of Borneo

About the photographs. Taken by Wong Fook Yee with a Canon PowerShot A480 on 26 June 2011 at 16:22:55, 16:24:03 and 16:24:10, beside the Tawau River opposite Pasar Semarak, Tawau, Sabah. Two of the three frames have never been opened in an editor. For this page they have been reduced, and two of them labelled, because a visitor wants to be shown what to look at. The unmarked originals are attached to the iNaturalist record above, which is where anyone working on the identification should start.

The family figures and the account of the larvae follow the published summary of the Buprestidae. The missing left wing case and hindwing are the photographer's own observation, made with the animal in his hand. All photographs © Wong Fook Yee. Page written 14 September 2026.