Retire to Florida, lie around in the sun, and take it easy: It is a familiar urge, and apparently not just for humans. Nikos Papadopoulos, an entomologist at the University of California at Davis, has observed fruit flies enacting their own lazy retirement rituals when they hit old age.
While running an aging experiment, Papadopoulos caught some of his oldest fruit flies lying upside down in their cages. At first sight, the elderly insects seemed to be dead, but they were merely resting on their backs. When Papadopoulos poked them with a pencil, they flipped over and began walking about, flapping their wings and seeking food and sex. In the wild, a supine fly would never survive; it would quickly be eaten. That might explain why such behavior has never been seen before. But these flies had been cosseted by Papadopoulos, who tended 203 male Mediterranean fruit flies until they died of old age at about 61 days. Beginning about 16 days before their deaths, nearly all the increasingly feeble flies spent up to an hour or more a day upside down.
According to Papadopoulos's colleague James Carey, this behavior may signal some form of neurodegenerative disease similar to Parkinson's or narcolepsy in humans. If so, the insects may provide an ideal model for studying such disorders. "This is not a quirk," says Carey. "This behavior is universal, progressive, and persistent. Now we have a model system where you can ask questions about the onset of this disabled period and whether you can postpone or compress it."