Why is that wasp helping?

For the first time, researchers have found nests of a social insect with helpers that are neither close kin nor slaves.

In the wasp species Polistes dominulus, about a third of females nest with an unrelated female. In the arrangement, one becomes the queen and the other submits to a nonreproductive working life, reports David C. Queller of Rice University in Houston. He and his Rice colleagues cooperated with a team from the University of Florence on the wasp-helper analysis, published in the June 15 NATURE.

When social insects forgo their own chance for reproduction to help raise close relatives, the strategy makes sense to people: The next generation that the insects are raising carries many of their genes.

Researchers have also known of wasp households with unrelated members. In one arrangement, two females sometimes work together to start a colony, but usually, both keep reproducing. In another, workers submit to unrelated, usurper queens late in the season--when it's too late to start a colony of their own.

Neither pattern fits what Queller and his colleagues saw in wasp colonies collected in central Italy. Genetic markers revealed within nests a bunch of unrelated females as well as full sisters. Yet all participated in raising the queen's offspring.

The most probable benefit for the submissive females, Queller and his colleagues speculate, comes from the chance that the queen will die during the summer, giving an unrelated wasp a chance to take over. That gamble paid off in 6 of 49 cases the researchers studied.