Paper Wasps Beg Their Young for a Saliva Snack

August 17, 2005

Parents across the globe usually take their role as providers very seriously. But in an unusual role reversal, paper wasp queens beg their young for a meal.

When they get peckish, the queens wag their abdomens across their nests, creating vibrations that "ask" for a nutritious saliva snack.

"She does it when she's hungry, not when the larvae are hungry. So the adult is begging for food back from the larvae," said Bernard Brennan, the postdoctoral researcher at Yale University in New Haven, Connecticut, who made the discovery.

Paper wasps (Polistes dominulus) are among the best studied insects in the world. But the reason for the queens' wagging behavior remained a mystery until Brennan started researching it as a graduate student at Cornell University in Ithaca, New York.

The evolutionary biologist presented his most recent findings last week at the annual meeting of the Animal Behavior Society in Snowbird, Utah.

Brennan's research shows how the wasps manage their food supply between the queen and her young. It also unmasks the surprisingly active role the young wasps play in the relationship: They control how much saliva they give up.

"This is certainly a fascinating example of parent-offspring communication, in a context where adults are not only feeding the young, but also being fed by them," Rex Cocroft wrote in an e-mail to National Geographic News. Cocroft is a biologist who studies animal communication systems at the University of Missouri in Columbia.

Liquid Diet

Like all adult wasps, bees, and ants, adult paper wasps are limited to liquid diets, because a section of their bodies between the head and the abdomen is extremely narrow. Solid chunks of food just wouldn't fit through.

"All digestion occurs in the abdomen, so their food has to get through this constriction," Brennan, the Yale biologist, said.

But wasp larvae, which are shaped more like fat worms, are able to eat a wider range of food.

Adult paper wasps—usually queens—exploit this difference by capturing caterpillars and feeding them to larvae in the nest. The larvae digest the caterpillars and produce nutrient-loaded saliva that is fed back to the adults.

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