The Life of an Ant: From an Egg Smaller Than a Pinhead to a Colony of Thousands

Lift a paving stone in a garden in summer and you might see it: a scramble of small black ants, and among them, dozens of pale, rice-shaped bundles being carried to safety. Those bundles are the next generation. Every one of the ants doing the carrying started out the same way, as an egg smaller than a pinhead.

This is the life of the black garden ant, Lasius niger, one of the most common ants in Europe and one of the best studied. Its whole life happens a few inches under our feet, and most of us never see any of it.

Egg, larva, cocoon

An ant egg is about half a millimetre long. It hatches into a larva, a soft, legless grub that cannot feed itself. Adult workers feed it by mouth, clean it, and move it around the nest to keep it at the right temperature and humidity. The larva grows and molts several times, then spins a silk cocoon around itself. Inside, it becomes a pupa, and its adult body forms.

Those cocoons are what people often call "ant eggs" when a nest is disturbed. They are not eggs at all. They are nearly finished ants, and the workers will risk everything to carry them away from danger.

When the adult is ready, workers help it out of the cocoon. She is pale at first and darkens over a few days. And it is a she: every worker ant in the colony is female.

A job that changes with age

A new worker does not head straight outside. In many ant species, including garden ants, work follows age. The youngest workers stay deep in the nest as nurses, feeding larvae and tending the queen. As they get older, they move toward the entrance and take on riskier jobs, like defending the nest and foraging.

It makes sense once you think about it. The outside world is where ants get eaten, trodden on, and lost. A colony loses less by sending its oldest workers into danger, since they have fewer days left to give.

Foragers bring home insects, seeds, and sugar. Black garden ants are famous for one particular source of sugar: aphids. The ants guard aphids on plant stems and "milk" them for honeydew, a sweet liquid the aphids release. It is one of the best-known partnerships in the insect world, and it is why gardeners often find ants and aphids together.

The queen who outlives everyone

A worker lives a short life, often a year or two at most. The queen is a different story. She is the only one laying eggs, and she can keep doing it for a very long time. A black garden ant queen kept in a laboratory in Germany lived for about 28 years and 8 months, one of the longest lifespans recorded for any insect. In the wild, queens rarely get that long, but they still outlive their workers many times over.

A mature colony can hold several thousand workers, and every one of them is her daughter.

Flying ant day

Once a colony is big enough, the queen starts producing something new: winged young queens and winged males. They stay in the nest until the weather is right, usually a warm, humid day in mid to late summer. Then, often across a whole region at once, they pour out and take to the air. In Britain this is so noticeable that people call it "flying ant day."

This is the nuptial flight. Queens and males from many colonies meet and mate in the air. The males die soon after. Each mated queen lands, breaks off her own wings, and digs a small chamber in the soil. She seals herself in and lays her first eggs, raising the first tiny workers alone, living on her own stored fat until they can forage for her.

If she survives that first year, and most do not, she can rule a colony of thousands for decades. And every one of those ants will start the same way she did: as an egg smaller than a pinhead.

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Frequently Asked Questions

What is the life cycle of an ant?

Ants go through four stages: egg, larva, pupa and adult. Workers feed and clean the larvae, which spin cocoons and turn into adults inside them.

How long does a queen ant live?

Much longer than her workers. A black garden ant queen kept in a lab lived about 28 years. Workers usually live a year or two.

What is flying ant day?

A warm, humid summer day when winged queens and males leave many colonies at once to mate in the air. Mated queens then shed their wings and start new colonies.

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Sources

• Lasius niger (black garden ant), species overview, colony size, aphid tending, and the record queen lifespan of about 28 years in captivity.
• Ant: life cycle and division of labour, egg, larva and pupa stages, female workers, and age-based task changes.
• Encyclopaedia Britannica: Ant, general ant biology, castes, and colony founding.
• Nuptial flight, how winged queens and males leave the nest to mate, and how new queens found colonies.
• RSPB: Ants, garden ants in Britain and the summer flying ant swarms.

Photo: black garden ant nest with workers and cocoons, Chapeltoun, North Ayrshire, via Wikimedia Commons (CC BY-SA 4.0).

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