National Geographic News
Photo: Wasp on bait near ants

A wasp crawls over bait swarming with ants during a research experiment.

Photograph by Julien Grangier, Victoria University of Wellington

Matt Kaplan

for National Geographic News

Published April 6, 2011

Looking for a way to banish ants from your picnic? According to a new study, wasps have developed a unique method for dealing with the pests: airlifting them away from the food.

In an experiment done with wild insects, scientists in New Zealand recently witnessed the common wasp, an alien invader to the island country, competing for food with the native ant species Prolasius advenus.

When a wasp approached a mound of food swarming with ants, the wasp would pluck an ant from the pile, fly a ways off, and drop the still-living insect from its jaws.

Watch silent video clips of the wasps dropping ants.

"To the best of our knowledge, this behavior has never been described before," said study co-author Julien Grangier, a biologist at Victoria University of Wellington.

(Related: "Parasitic Wasp Swarm Unleashed to Fight Pests.")

Wasps Bigger, But Not Badder

Common wasps (Vespula vulgaris) are native to North America but were accidentally introduced to New Zealand in the 1970s. The wasps eat other insects and nectar, capturing live prey or scavenging.

(Related: "Alien-Wasp Swarms Devouring Birds, Bugs in Hawaii.")

Grangier and colleague Philip Lester had suspected that the alien wasps were competing with native ants for scarce protein sources in New Zealand beech forests.

This led the pair to establish an experiment in which ants and wasps were presented with samples of high-protein food: little chunks of tuna fish.

The samples were placed at 48 stations in a natural beech forest, with cameras set up near each one. Both wasps and ants visited 45 of the 48 stations, and the cameras recorded 1,295 interactions between the insects.

In the vast majority of instances, the wasps and ants avoided or ignored each other. However, the researchers documented 341 cases when the ants were aggressive toward the wasps, charging at the larger bugs, biting them, or spraying them with formic acid, a natural defense mechanism.

(Related: "Ants Use Acid to Make 'Gardens' in Amazon, Study Says.")

In just 90 encounters the wasps were the aggressors, including 62 cases of ant dropping. The researchers suspect the other 28 times were ant-dropping attempts that the wasps fumbled.

"It was a surprise to see that ants, being 200 times smaller than wasps, can be serious competitors with them," Grangier said.

Ant Acid Behind Wasp Behavior?

Most of the time, the wasps' ant-dropping behavior was unprovoked, with ants being simply grabbed and flown away. In a few instances the ants were unruly before they were grappled and carried off.

The team argues that the acid defense may be why the wasps "ant drop" rather than just killing the smaller insects outright.

"By not crushing ants and dropping them away as fast as possible, wasps just protect themselves, avoiding further contact with this harmful substance," Grangier said.

The wasps' ant-dropping behavior is described in a study published online March 30 by the journal Current Biology.

Also see related pictures: "'Zombie' Ants Found With New Mind-Control Fungi" >>



Popular Stories

  • 'Extinct' Bird Rediscovered in Myanmar

    'Extinct' Bird Rediscovered in Myanmar

    The Myanmar Jerdon's babbler was thought to have gone the way of the dodo—until scientists stumbled across it during a 2014 expedition.

  • Lost City Found in Honduras

    Lost City Found in Honduras

    A joint Honduran-American expedition has confirmed the presence of extensive pre-Columbian ruins in Mosquitia in eastern Honduras, a region rumored to contain ruins of a lost "White City" or "City of the Monkey God."

  • Astronomers Find a Galaxy That Shouldn't Exist

    Astronomers Find a Galaxy That Shouldn't Exist

    Small, young galaxies should be free of interstellar dust, but an object called A1689-zD1 is breaking all the rules.

The Future of Food

  • Why Food Matters

    Why Food Matters

    How do we feed nine billion people by 2050, and how do we do so sustainably?

  • Download: Free iPad App

    Download: Free iPad App

    We've made our magazine's best stories about the future of food available in a free iPad app.

See more food news, photos, and videos »