Paper wasps follow a secret succession line

Royal successions in human history have often been violent and disorderly affairs. These bloody power struggles are seen in the insect kingdom as well, where emerging queen bees kill virgin queens and breeding termites fight over the right to pass on their genes — but this is not the case with paper wasps.

When it comes to selecting their next queen, some paper wasps are surprisingly peaceful, a recent study published in the Proceedings of the National Academy of Sciences suggests. These insects seem to have an innate sense of their position in the succession line, and when the time comes for a new queen to take the throne, she is allowed to rule without riot or squabble. This is contrary to the common law of the insect world, rife with wars over territory and the right to pass on genetic material.

When researchers Alok Bang and Raghavendra Gadagkar of India removed the queen from a colony of south Indian paper wasps, Ropalidia marginata, they observed that within 30 to 45 minutes another female wasp displayed aggressive behavior and took up the position of queen. This hyper-aggressive wasp, which the researchers call a “potential queen,” initially dominated the others by pecking, nibbling and crushing them. Eventually, she calmed down and began developing ovaries. Within the next few days she began laying eggs. When the new queen was removed, another wasp promptly proclaimed herself sovereign, a pattern that held in 19 different colonies through five consecutive successions.

“As far as we know, this [behavior] is unique among the social wasps,” said Robert Jeanne, professor emeritus at the University of Wisconsin- Madison and an expert on the behavior of social insects.

In the line of succession, called the reproductive queue, older wasps generally came first, to scientists’ surprise. “I would have expected that the potential queen would come from the younger wasps as they would have more energy to get their ovaries working in a short time,” said James Hunt, a social insect researcher at North Carolina State University also not affiliated with the study. “But their research suggests the opposite, which is an enigma to me.”

This swift, conflict-free way of selecting the next heir is most likely an evolutionary strategy to avoid a gap period without a reigning queen, an anarchic period that could leave the group vulnerable to intruders. The queue might also give potential queens the choice to wait their turn to reproduce or leave the nest and begin a colony of their own.

Scientists are not sure what triggers this efficient replacement process or how wasps can tell when the queen is missing. Honeybee queens release a complex mix of compounds, called queen’s substance, that other bees recognize as “royal.” When that substance is absent, the honeybees know that they need a new queen. “It is plausible,” said Hunt, “that some kind of queen substance or pheromone might be involved in wasps as well.”

Whatever their method may be, it seems that while the rest of the insect kingdom continues to display signs of struggle, the evolutionary adaptive mechanisms of these wasps have led them to adopt a Gandhian queen selection process.