Ratnieks and Wenseleers, his former postdoctoral student, recently examined policing patterns in ten insect species.
In some, such as the Asian paper wasp, the queen personally kills and consumes eggs that her daughters lay.
In other species, including honeybees, loyal workers assist the queen by eating the eggs of insubordinate workers who attempted to spawn.
(See related photo: "Oldest-Ever Bee Found in Amber" [October 25, 2006].)
As many as one-third of Asian paper wasps—but fewer than one honeybee in a thousand—lay eggs, the researchers report in the November 2 issue of the journal Nature.
While most worker-laid eggs survive in Asian paper wasp colonies, nearly all get killed in honeybee hives, the researchers found.
"Egg-killing helps to retain the reproductive monopoly of the queen," Wenseleers said.
"If there is a very high probability of [workers' eggs] being killed," he said, "then there's not much point in them laying the eggs in the first place."
In effect, insect colonies enforce a sort of zero-offspring policy.
That manipulation explains why most honeybee workers essentially abandon any design on bearing offspring, Wenseleers says.
"Their seeming altruism is not really voluntary."
Family Ties
If voluntary altruism drove workers to favor their kin's welfare over their own propagation, then closely related workers would be more cooperative than ones who weren't related.
"We actually find the reverse," Wenseleers said. "The less closely related, the more cooperative they are."
Asian paper wasp workers, for instance, share 75 percent of their genes with each of their nest-mates, but they lay more eggs. The more altruistic honeybees are only about 30 percent related to one another.
This suggests that "altruism is not based on family ties," Wenseleers said. "It's based on social coercion."
"Some individuals are manipulating the options that other individuals have," commented David Queller, an evolutionary biologist at Rice University in Houston.
For workers deprived of the chance to reproduce, helping their mother and sisters is their best shot at perpetuating their genes, he says.
This lesson might have implications for human societies, Wenseleers adds.
"Cooperation is possible even among genetically unrelated strangers," he said.
On the other hand, the lesson shouldn't be taken too literally, he says.
"A society where everyone is very cooperative out of fear for being punished is not the sort of society you would want to live in."
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