Pictures: Wasps Turn Ladybugs Into Flailing "Zombies"

Emerging Larva

Photograph courtesy Mathieu Bélanger Morin

A wormlike wasp larva emerges from its ladybug host in a recent picture.

Although most parasites eventually kill their hosts, the wasp-infected ladybugs have a more "atypical fate," according to the study—some ladybugs survive their "horrible" ordeal. For example, Brodeur's team observed in field experiments that 30 to 40 percent of the infected ladybugs lived after the young wasp hatched, including some individuals that later laid their own eggs.

The host bug can survive because the wasp larva feeds only on tissues that are not crucial for the ladybug's survival, such as fat, the scientists say.

(See "Parasitic Wasp Swarm Unleashed to Fight Pests.")

Published August 2, 2011

"Bodyguard" On Duty

Photograph courtesy Mathieu Bélanger Morin

Once a still living ladybug takes up its post on top of the wasp cocoon—as seen in a recent picture—the insect will act aggressively toward intruders, for example, by flailing its legs. The scientists suspect the twitching behavior comes from venom left in the ladybug's body after the larva emerges and builds its cocoon.

In the lab, Brodeur and his team placed predatory lacewings into petri dishes that contained either cocoons covered by live ladybugs, other cocoons covered by dead ladybugs, or cocoons that lacked ladybug bodyguards.

The results showed that the lacewings were less successful in attacking cocoons being protected by the "zombified" ladybugs.

(Also see "Genetically Altered Plant Attracts Bug 'Bodyguards.'")

Published August 2, 2011

Wasps in Waiting

Photograph courtesy Mathieu Bélanger Morin

The length of time that a wasp larva manipulated a ladybug into protecting its cocoon also varied from insect to insect. In some cases the ladybug stayed vigilant until the larva emerged from its cocoon as a young wasp. In other cases the ladybug was under the wasp's sway for just a few days, Brodeur noted.

The team found that wasp larvae that invested more time and energy into controlling their ladybug bodyguards laid fewer of their own eggs as adults than the larvae that did not.

It's the first time that scientists have shown a trade-off between host manipulation and
fertility, he said.

Published August 2, 2011

Wiry Cocoon

Photograph by Kees van der Krieke, Stippen.nl

A D. coccinellae wasp cocoon is seen in a closeup picture. The species is widespread throughout the world, including in Asia and Europe, Brodeur said: "It's quite cosmopolitan."

But the parasites are very haughty when choosing their bodyguards: They'll infect only ladybugs.

(See "Alien Wasps Abduct, Drop Ants to Get Food.")

Published August 2, 2011

Newborn Wasp

Photograph by Kees van der Krieke, Stippen.nl

Eventually a new wasp, like the one seen above, emerges from the protected cocoon.

With his new research, Brodeur said he has solved a mystery that arose during an outdoor stroll in Canada.

"It's quite common when you are out in the forest to see ladybugs on top of a cocoon—we were wondering why it was like that," he said.

(See "Ancient Wasps Roosted in Rotting Dinosaur Eggs?")

Published August 2, 2011