By Susan Milius
From Snowbird, Utah, at a meeting of the Animal Behavior Society
A former whale-acoustics analyst says that he has for the first time decoded a vibrational signal by paper wasps.
Biologists have known that a female paper wasp frequently presses her abdomen against cells in her nest and waggles, says Bernard Brennan of Cornell University. To study this phenomenon, he focused on a brand-new nest where the founding female was tending to her first 20 or so larvae. He removed one larva and put a tiny vibration sensor in its place. The resulting data indicate that the queen’s vibrations spread throughout the nest.
To look for the intended receiver of the vibrational signals, Brennan painstakingly removed all larvae from their nursery cells. He found that a mother returning to an empty nest waggled at first, but quickly stopped. When Brennan eased the larvae back into place, the female began waggling again. These observations suggest that the vibrations are signals for larvae, he says.
Brennan suspected that the signals have something to do with feeding. In an extensive series of experiments, he considered whether the signal might be connected to the larvae feeding saliva to their mother.
In one set of tests, Brennan deprived the queen of her usual liquid diet, while hand feeding bits of ground-up caterpillar to the larvae every hour. The queen continued her occasional waggling. The tests suggested to Brennan that the vibrations indicate hunger of the adult, not of the larvae.
In another set of experiments, he mounted nests on a finely controlled mechanical shaker to mimic the queen’s waggling. In response to a nest trembling, he measured saliva increasing in the mouths of the larvae. He concluded that a hungry wasp waggles to signal her youngsters to start drooling.
