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October 19, 2009

Social Insects


A sting operation to get the dirt on yellow jackets

"Did you get stung the other day?" a biology graduate student asks as he pulls on a white coverall over his jeans.

"Sure did," says Michael Goodisman. "That thing hit me in the ankle, it hurt like crazy!"

Learning the secrets of the birds and the bees, and the wasps can be a hazardous pursuit. Georgia Institute of Technology biology professor Michael Goodisman, along with two of his graduate students, are suiting-up, willing to take it on the ankle and wherever else the aggressive yellow jackets may sting.

Homeowner Roger Bakeman had phoned Goodisman as Bakeman had done the year before. The yellow jackets had returned to Bakeman's backyard. He knew Goodisman would be willing to dig up the nests to study the stinging wasps. They're the focus of Goodisman's recent studies at Georgia Tech. No coincidence that the yellow jacket is the school's mascot.

"They make me abandon a 10-foot radius of my yard," complains Bakeman. "They're the nastiest and most aggressive insects I've encountered."

Bringing them back alive

"Alright, it's time to zip in," says Goodisman as he pulls on his netted helmet. "Want me to zip you in? OK, let's put the gloves on."

As the yellow jacket squad makes its way into the backyard, Goodisman is quick to locate the first small hole in the ground where the nest is likely buried, about three feet from Bakeman's back door.

"They've built nests in bad places, underneath plants and near houses, so they are a pest," Goodisman says. "OK, pour a little ether down their entrance hole--that's going to anesthetize them. We will dig them out of the ground while they're still alive."

He carefully digs down about six inches and pulls out a big nest--about a foot long and five-layers thick. Each layer is a comb with tiny holes or cells similar to a honeybee's comb, where the queen lays her eggs. One flat comb stacked one upon the other connected by tiny half inch pegs. Good little architects, these yellow jackets!

"Ohhh, she's a big one," says Goodisman. He examines the nest and places it into a plastic container. "Not a lot of workers, very interesting." Goodisman and his team start looking for the next nest--all this to find out what goes on in the yellow jacket queen's boudoir, if you will. Goodisman is studying the sex lives of yellow jackets by studying their DNA.

Yellow jackets are wasps, and though they seem eager to inflict pain, they do have some important redeeming qualities. They kill harmful garden pests and are among the most social insects on the planet, along with their stinging cousins, the ants and the social bees.

Life in the colony

"Yellow jackets are very much like honeybees and fire ants," says Goodisman, "in that they have a single queen that heads the colony, and a bunch of her worker-daughter offspring. Social insects are defined by three different criteria: The first is that there is an overlap of adult generations where a mother lives together with her daughter offspring. The second is that there is cooperative brood care, which means that lots of individuals help rear the young together. The third is the most important criterion--there is a reproductive division of labor."

In the case of the yellow jackets, fire ants and honeybees, the queen lays all the eggs and the workers service the queen and help her raise the young. "It is so extraordinary that you have this sterile worker or soldier cast that basically doesn't reproduce at all; this is what makes social insects so extreme and so bizarre. We are interested in studying the evolution of these traits," says Goodisman.

"There's the queen," he says as the team unearths another nest from the backyard. "The queen is the larger individual surrounded by her daughter offspring, the workers."

Workers are all female, he explains. Males are for mating only. Most social insect queens will mate once a season with one male, enough to collect all the sperm she needs to lay her eggs. The offspring will all be related to each other--one big happy family.

This is not the case with yellow jackets, however. Goodisman is finding that yellow jacket queens are 'players'. DNA testing reveals that, unlike honeybees, the yellow jacket queens have multiple sex partners. So instead of sister workers, half sisters guard the nest and feed the queen. Goodisman is using National Science Foundation (NSF) support to try and understand these complex relationships and how they impact these intricate communities.

"There's a big question out there about why animals of any species would mate multiple males," he says.

Extreme teamworkers

Goodisman is not just focused on sex. He is also curious how social insects within a community work as a team, where a queen cannot survive without a worker and a worker without a queen. To better understand these close relationships, he also studies fire ants which are more kin to yellow jackets than honeybees.

"Ants are very closely related to social wasps," says Goodisman. "Think of ants as wasps without wings that have given up the life of flying and decided to live on the ground. Bees are wasps that have become vegetarian. Most ants and wasps eat meat--they eat other insects--but honeybees eat pollen and nectar."

At a Georgia Tech physics lab run by fellow researcher and physics professor Daniel Goldman, photographs and x-rays are set up to capture fire ants at work digging intricate tunnels. For these ants, caring for their brood and keeping their queen safe are more important than their own lives.

In three buckets, Goodisman demonstrates their allegiance. Each bucket contains a floating brown blob; each blob is made up entirely of fire ants.

"Fire ants do form these living rafts of ants, when they get flooded," he explains. "They basically float on their young and they'll cannibalize each other to some extent until they hit land. Ants die but the colony survives, that's what it is all about. The colony survives, the queen survives."

The making of the queen

"That is the queen," he says, adding "she's very different than the workers, much larger than the workers. The male has wings. It's got a little tiny head and big shoulders. That's a running joke. They're basically all muscle and very little brain. They don't have much to do but fly off and mate."

Like yellow jackets, fire ant males live for the chance to mate with the queen, and all the workers are females.

Another puzzle Goodisman hopes to solve is what makes a queen a queen? Her DNA does not differ from her fellow worker females but she definitely stands out in the crowd.

"The queens are much larger, they are built differently, they are really completely different from the workers."

To help determine the differences that separate queen from worker yellow jackets, Goodisman studies their living quarters. There are obvious differences. The queen is reared from a different part of the nest. Within her quarters, or comb, the cells are much larger than the workers' and Goodisman believes that may make a difference. He hopes in the next few years to have a better understanding and might even impart some insight into who we are.

Insight into other social animals

"Humans are social animals," he explains. "We're not as social as the insects but the same kinds of pressure, the same kinds of problems that occur in insect societies occur in human societies. Do we have conflicts in social insects' societies where you have multiple families? Do we see the same thing in humans? Why do people tend to help their relatives more than others? Is there an evolutionary reason for that? These kinds of questions apply across the animal kingdom, and in studying insects, we can really get the most detailed levels of understanding of social behavior."

Meanwhile, back in that yellow jacket plagued backyard, the hunt is nearing its end as the research team unearths the third nest. "Alright, let's get this sucker out of the ground. Alright, we're good," Goodisman says as he places the last nest in a plastic bin and seals it shut with duct tape for the ride back to the lab.

The hunt is a success, the homeowner has reclaimed his garden and the researchers leave with nary a sting. Goodisman proclaims: "Nicely done--victory over the yellow jackets!"

Careful how loud you say that on this college campus!

Miles O'Brien, Science Nation Correspondent
Ann Kellan, Science Nation Producer


Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.