How paper wasp colonies survive the loss of their queen

When a queen vanishes from a paper wasp colony, disorder might seem unavoidable. A nest organised around a single dominant, egg-laying female suddenly loses its centre.

Other females are capable of breeding, tensions mount and the colony’s future becomes uncertain. Such struggles for power can break apart groups in many animal societies.

One tropical paper wasp, however, has a way of weathering the upheaval.

In a recent study, researchers from University College London (UCL) and the Zoological Society of London (ZSL) examined how the tropical paper wasp Polistes canadensis responds to the loss of its queen.

Their findings reveal a striking balance of cooperation and conflict within these small societies.

One female controls the paper wasp colony

Cooperative breeding occurs throughout the animal kingdom. Meerkats, naked mole rats, cichlid fish and paper wasps all live in societies with a similar arrangement.

Most offspring are produced by one female, while the others help to rear the young.

Unlike honey bee workers, these helpers are not sterile. Given the chance, they can reproduce themselves.

The disappearance of the dominant breeder therefore creates a serious difficulty: every helper is a potential successor.

The colony has to establish who will take her place, but that process is risky. Fighting can interrupt food gathering, brood care and defence.

Should the dispute continue for too long, the colony could collapse before another queen takes charge.

Removing the queen

Polistes canadensis inhabits tropical forests and towns across Central America.

Earlier observations had shown that the wasps become extremely aggressive when they lose a queen.

Even so, their colonies generally survive. The researchers set out to find out why.

Working at four sites in Panama’s Canal Zone, the team followed 306 wasps in 19 colonies. Each individual was marked with tiny dots of coloured paint.

The researchers recorded thousands of behavioural interactions over time.

They then performed the key experiment: removing the queen.

Conflict after queen loss

Before the queen was removed, life in the colonies seemed comparatively peaceful. The queen was responsible for most aggressive behaviour, while workers carried out tasks such as hunting caterpillars and feeding larvae.

Within 24 hours of her disappearance, that changed completely.

Aggression rose approximately tenfold. More wasps became involved in physical fights, and workers started attacking each other rather than simply being on the receiving end of the queen’s aggression.

In some colonies, more than 40 percent of workers took part in the conflict. Instead of one challenger, multiple rivals turned the nest into a battlefield.

Identity of the future queen

The identity of the eventual winner was among the study’s greatest surprises.

Before the queen disappeared, her successor showed no distinguishing traits. She was no larger, more aggressive or more dominant than the other females.

Nor did the original queen appear to favour her.

The successful female only began to distinguish herself several days into the conflict.

This suggests that the colony has no hidden line of succession.

Instead, once the queen is gone, direct competition must determine who inherits her position.

Colony work does not stop

On the face of it, the situation looks disastrous.

If many workers are occupied with fighting, who hunts for food and feeds the larvae? During succession battles in many species, those duties break down.

Polistes canadensis, though, avoided that result.

After the queen was removed, foraging rates remained surprisingly steady, and food-sharing networks held together.

Even amid intense conflict, the colony continued to feed its brood. The reason proved remarkably clever.

Workers change jobs

The researchers found that many wasps which had previously gathered food stopped foraging and joined the contest for dominance.

Meanwhile, other wasps never previously seen foraging began leaving the nest to collect food.

As competitors fought for the throne, these replacement workers met the colony’s everyday needs. Nearly 70 percent of foragers after queen removal came from this newly active group.

In effect, the colony divided into two camps: one fought for reproductive power, while the other kept society functioning.

“The conflict after queen removal was intense, but it wasn’t the whole story,” said the study’s lead author, Dr Owen Corbett.

“While some individuals fought over dominance, others completely avoided the conflict and quietly stepped up to keep the colony running. Cooperation didn’t disappear; it was redistributed.”

Idle wasps avoid responsibility

The researchers had expected inactive colony members to serve as an emergency reserve workforce. Instead, that did not happen.

Even after the queen vanished, most previously inactive wasps stayed inactive.

It was active workers that had not been foraging who changed roles and compensated for the disruption.

The researchers still do not know what leads some wasps to compete while others steer clear of conflict.

Signals of fertility, differences in age or physiology could influence those choices.

Lessons beyond insects

The findings could have relevance well beyond paper wasps.

Aggression increases in many cooperative animals when a dominant female is lost. Yet only some individuals enter the competition, while others carry on with essential duties.

“Understanding how animal societies manage conflict can help us think differently about cooperation more broadly,” said the study’s senior author, Professor Seirian Sumner.

“In times of turmoil, society depends on those who keep doing the essential work in the background. In many ways, we may be more like wasps than we realise.”

For a tiny insect whose brain is smaller than a sesame seed, Polistes canadensis has developed an impressive answer to one of society’s oldest problems.

The throne may provoke conflict, but the colony survives because someone still feeds the next generation.