Not all pirate wasps have a tragic past.

The home wreckers, kidnappers, and hijackers of the paper wasp world may not all be driven to mayhem by broken homes. Instead, some of these wasps are playing out a novel sit-and-wait reproductive strategy, says Philip T. Starks of Cornell University.

The European wasp species Polistes dominulus landed in Massachusetts some 20 years ago. Its kingdom of papery combs now extends into the Midwest.

Lone females of the species sometimes buzz out of the sky onto another female's nest and take over, chasing away the original queen and eating her youngest offspring. The older offspring are allowed to live but must tend the eggs laid by the new ruler. Lone females also appropriate undefended nests whose founding females have died.

Researchers once assumed that these takeover artists had lost their own nests or been stuck as subordinate females in other queens' colonies. In the early 1990s, however, two behavioral ecologists proposed that some nest-grabbers had never bothered to build or tend a nest. These wasps just waited for the right moment to pirate somebody else's, suggested Peter Nonacs, now of the University of California, Los Angeles, and H. Kern Reeve of Cornell.

To test this idea, Starks established colonies of labeled wasps in a greenhouse and noted which captive wasps were tending nests and which were unaffiliated. He then collected more nests from the wild, removed the queens, and left the undefended combs and youngsters up for grabs in the greenhouse.

All the females who took over the introduced nests came from the population of floaters, Starks says. His analysis appears in the Aug. 7 Proceedings of the Royal Society of London B.

"It's a very risky behavior," Starks observes. A pirate female whose takeover bids fail hits a genetic dead end.

What prompts some females to lurk for takeover opportunities while others build nests? "I'm having a heck of a time figuring out the conditions," Starks says.

Nonacs notes that "nest-building is very dangerous too." Dashing around for nest fibers and food for her offspring exposes a wasp queen to spiders, praying mantises, and other killers. How many females in the wild dodge these risks early in the season and go into piracy is not clear from Starks' greenhouse test, Nonacs cautions.

He would not be surprised if other Polistes wasps include lurking takeover queens. "I don't think it's been looked for a lot," Nonacs says.