eTawau > Insects of Borneo > Ants > The green queen and the maggots

The green queen and the maggots

A weaver ant on a papaya leaf, Tawau — and a question I could not answer

One afternoon in July 2009 I was walking in a papaya garden beside the Tawau River, opposite Pasar Semarak at Km 7 of Jalan Kuhara. On a yellowing papaya leaf I found something I had never seen before, and I still think about it. Let me show it to you, and let us look at it together.

A dead green ant lying on a sheet of white silk that covers a hole in a yellowing papaya leaf. The ant's abdomen is swollen into a large round ball, far bigger than the rest of the body. Several small pale cream-coloured grubs lie on the abdomen, on the silk beneath the ant, and on the leaf beside it. Labels mark the head, the thorax, the waist, the swollen abdomen, the fly larvae and the silk sheet. — **Picture 1.** The whole animal. A dead ant, about 15 mm long, lying on a sheet of fine white silk across a hole in a dying papaya leaf. Look at the size of the abdomen, and count how many pale grubs you can find.

Take your time with that picture before you read on. Ask yourself three things. What kind of animal is this? What are the small pale things? And what happened here?

First, learn to read an ant

Your science textbook tells you that an insect has three parts: head, thorax and abdomen. That is correct, and it is worth remembering. But look at the ant in Picture 1 and count. You will see four pieces, not three.

The extra piece is the waist. In an ant the front part of the abdomen is pinched into a narrow stalk with a small lump on it, and behind that stalk the rest of the abdomen swells into a rounded ball. So the rule is not broken — the waist is part of the abdomen, not part of the thorax. It only looks like a separate section.

This narrow waist is one of the surest ways to know you are looking at a true ant. Many insects pretend to be ants, and some of them are very good at it, but a painted stripe is not the same thing as a real pinch. (If you want the harder version: the ant's "thorax" also contains the very first segment of the abdomen, fused on at the back. Scientists therefore use the words mesosoma and gaster rather than thorax and abdomen. Learn the simple version first.)

This one is a queen

Now look at the second picture — the front half of the same animal, larger.

A close view of the front half of the same green ant. Labels point to a large smooth domed plate on the thorax called the mesoscutum, a smaller plate behind it called the scutellum, a mass of crumpled dark brown material at the wing bases labelled wing remnants, the large dark eye on the head, a pale fly larva lying against the body, and the white silk sheet beneath. — **Picture 2.** The front half. The big smooth plates on the thorax and the crumpled brown remains at the wing bases are the marks of a queen. A worker ant has neither.

In an ant colony there are different kinds of ant, and they have different bodies. The ones you see running along a branch are workers. Workers never have wings and their thorax is simple and narrow, because there are no flight muscles inside it.

This ant is not a worker. Her thorax is deep and boxy and covered with large smooth plates — the big dome in front is called the mesoscutum and the smaller plate behind it the scutellum. Those plates exist to anchor wing muscles. And at the wing bases you can see a crumpled brown mess: what is left of her wings.

Here is the part I like best. A young queen grows wings, leaves her mother's nest and flies. She mates in the air. Then she lands — and she breaks her own wings off. She will never fly again and she does not need to. From that day she is a walking egg factory. The crumpled brown material in Picture 2 is the stump of a journey she made once and never repeated.

Why is she green, when kerengga are red?

Every child in Tawau knows the kerengga — the weaver ant, Oecophylla smaragdina. They are the fierce reddish ants that live in bundles of living leaves in mango, rambutan and other trees, and that come running out along your arm if you shake the branch.

So why is this ant green?

Because in Malaysia the workers are red but the queens are green — from dark green to a pale yellow-green. That is why almost nobody has seen one. The queen stays inside the nest, and the only time she is out in the open is on the day she flies. The scientific name says it plainly: smaragdina is Latin for emerald. The species was named for a colour that most people never get to see.

Am I certain? No, and I will not pretend. I am confident this is a weaver ant queen, because of the colour, the size, the long head with the big eye, and above all the silk. But I did not collect the specimen and I am not a specialist. That is why the record is also posted on iNaturalist, where scientists anywhere in the world can look at it and correct me. Being willing to be corrected is not a weakness. It is how the work is done.

The ant that builds with its own babies

Now, the silk. Look again at Picture 1 — the white sheet the ant is lying on, stretched across a hole in the leaf.

When I first saw it I thought of a spider. But it is almost certainly not a spider's web, and the reason is one of the most remarkable things any insect does.

A weaver ant nest is made of living leaves pulled together and glued with silk. But adult ants cannot make silk. Only their larvae — their own grubs — can. So the workers line up along the edge of a leaf, grip it, and haul. Other workers go into the nest, pick up a half-grown larva in their jaws, carry it out, and pass it back and forth across the seam like a living sewing shuttle, tapping its head so that it releases a thread. Leaf by leaf, thread by thread, they build a green house out of their own children.

A big nest — up to half a metre across — can be finished in less than a day.

So the silk on that papaya leaf may well be the remains of a nest. The leaf died and rotted away around it, and the silk, which does not rot so fast, stayed behind.

How big is a weaver ant colony?

Bigger than you are imagining.

A single colony can hold hundreds of nests spread through several trees.
It can contain more than half a million ants.
And normally there is one queen for all of it, sitting in one nest, laying the eggs that are then carried out to all the others.

Read that again, then look at Picture 1 once more. If this queen belonged to an established colony, then the small dead body on that leaf was the beginning of the end for every one of those ants. If she was instead a young queen who had just flown and was trying to start a colony of her own, then what died was a colony that never happened.

Either way, one ant on one leaf is not a small event.

The farmers' ant

There is a reason to care about weaver ants beyond their being interesting.

Farmers in South-East Asia — in China and Vietnam especially — have used weaver ants in their fruit orchards as pest control for hundreds of years. This is one of the oldest known uses of one animal to control another, and it works: weaver ants patrol the leaves day and night and attack the insects that damage cashew, mango, citrus, cocoa and coconut. In mango orchards where the ants were present, seed weevil damage was under 1%; where they were absent, it ran from 2.5% up to 16%.

I found this queen in a papaya garden. Think about that. The ant that some people knock down with a stick because it bites is, in other countries, deliberately encouraged and even moved from tree to tree by farmers who understand what it is doing for them.

What happened to her abdomen?

A close view of the swollen green abdomen of the same ant. Labels point to two pale fly larvae lying in the gaps, to one of the hard dark green plates of the abdomen, and to the pale soft skin between the plates which has been stretched into wide bands. — **Picture 3.** The abdomen, close up. The dark green pieces are the hard plates. The pale bands between them are soft skin, pulled tight. This is not how a living ant looks.

An insect's abdomen is not one solid box. It is a row of hard plates joined by soft, flexible skin, so that the animal can bend and swell. In Picture 3 that soft skin has been stretched to its limit. The plates have been pushed apart until you can see straight through to the pale membrane between them, and the whole abdomen is tight like a balloon.

And sitting in those gaps are the pale grubs.

Are those baby ants?

A fair guess — there are ant larvae in every ant nest, after all. But no, and here is how to tell, because this is a useful thing to be able to do.

An ant larva has a head. It is small, but it is a distinct capsule with tiny jaws on it, and the body is usually plump and curved like a comma.
A fly larva — a maggot — has no head at all. It is a smooth ringed cylinder that tapers to a soft point at one end and is cut off blunt at the other. There is nothing you could call a face.

Look at the grubs in Picture 1 and Picture 3. Smooth rings, a soft point at one end, blunt at the other, no head. These are fly larvae. They are not the ant's children.

Now the hard question

Here it is, and I want you to notice that I am not going to answer it.

Did those maggots kill this queen, or did they simply find her already dead?

When I first saw the photographs, my own answer was immediate: parasites, eating her alive from the inside. That is what it looks like. But "what it looks like" and "what happened" are not the same thing, and a good observer keeps them apart. So let us set out both sides properly, the way you would in an argument where you actually want to find out the truth rather than win.

The case that they killed her

They really do appear to be coming out from inside the abdomen, through the stretched skin.
Her skin is not torn or chewed open. She is swollen and stretched, not opened up.
Insects that live inside other insects and eat them are real and common. They are called parasitoids, and there are many in Borneo that nobody has studied.

The case that they found her dead

The flies that are known to parasitise ants — mostly a family called Phoridae — lay one egg per ant. One larva, one host. Here there are many.
The larvae are all about the same size. That is what one batch of eggs, laid at one moment, looks like. It is exactly how a fly that lays on dead flesh behaves.
A dead body swells by itself. When any animal dies, bacteria inside it produce gas, and that gas pushes the abdomen tight and forces the plates apart. The stretched skin between the plates is then the softest place for a maggot to work its way in — whether it arrived before she died or three days after.

So which is it? On the evidence in front of us, I think the second explanation is more likely — that she died of something else and the flies came afterwards. But I am not sure, and the photographs cannot make me sure. So the honest answer is: I do not know.

That sentence is not a failure. Learning to say it clearly, and then to say what would settle it, is most of what science actually is.

What would settle it

Keep the larvae and raise them. Put them in a covered container with the ant and wait for the adult flies. Name the fly and you very nearly have your answer, because the family a fly belongs to tells you how it lives.
Open the ant and look. If her own muscles and organs had been eaten away while her skin stayed whole, something was living inside her.
Watch the timing. If you ever find a weaver ant behaving strangely and can go back to it the next day, you will see with your own eyes whether the larvae arrive before or after death. That is the strongest evidence of all, and it costs nothing but patience.

Words to know

Colony: All the ants of one family living together — here, possibly half a million of them.
Worker: A female ant that does not reproduce. She has no wings, ever. Nearly every ant you see is a worker.
Queen: The female that lays the eggs. She grows wings, flies once, mates, then breaks her wings off.
Larva: The young, growing stage of an insect — a grub or caterpillar. Plural: larvae.
Maggot: The larva of a fly. No head capsule, no legs.
Parasitoid: An animal that develops inside another animal and kills it in the process. Different from a parasite, which usually keeps its host alive.
Scavenger: An animal that eats things that are already dead.
Kerengga: The Malay name for the weaver ant, Oecophylla smaragdina.

Questions to think about

The workers of this species are red and the queens are green. Why might it not matter to the ant what colour its queen is, when she spends her whole life in the dark inside a nest?
Weaver ants cannot make silk as adults, only as larvae. What does that tell you about how much the colony depends on having young in it at all times?
If a colony has only one queen, and half a million workers, what is the colony's greatest weakness?
I gave two explanations for the maggots. Can you think of a third that I have missed?
Suppose you believed the first explanation because it is more exciting. What would that cost you?

If you go looking for weaver ants — and you should. They are easy to find in almost any fruit tree in Tawau. They do not sting, but they bite hard and then spray formic acid into the bite, which stings properly for a while. Look at the nest, photograph it, and do not tear it open: inside are the larvae the whole colony depends on, and a nest pulled apart is weeks of work destroyed. Watch instead. A weaver ant nest in the afternoon is better than most television.

Where and when

Place: a papaya garden beside the Tawau River, opposite Pasar Semarak, Km 7 Jalan Kuhara, Tawau, Sabah — on the far side of Jalan Kuhara, so outside the Tawau River Triangle, and about as close to it as you can stand.
Date: 19 July 2009, about 5.30 in the afternoon.
Size: about 15 mm, with the abdomen already swollen.
The record: iNaturalist observation 398990434. If a specialist adds an identification there, I will correct this page to match.

Tawau River Triangle — the abandoned plantation by the Tawau River, across the road from this papaya garden, and the other records made there
A black butterfly caterpillar with blue spines · A caterpillar with its bristles in bunches · A tussock moth caterpillar on a palm — the other three records from this same papaya garden, 2007, 2008 and 2011
Ants of Tawau and Borneo — how to tell a real ant from an imitation
A black ant on a grass stem
A spiny ant on dead wood
An ant that is not an ant — an insect pretending, and how it gives itself away
Insects of Borneo

About the photographs. Three frames taken by Wong Fook Yee on 19 July 2009 with a Canon PowerShot A470, within one minute of each other. On this page they have been reduced, and labels have been added, because this page is written to teach rather than to serve as scientific evidence. The unmarked full-resolution originals are attached to the iNaturalist record above, and those are the ones a scientist should work from.

All photographs © Wong Fook Yee. Page written 10 September 2026.