A report by Greg Miller in the November 25, 2005 issue of Science magazine (vol. 310. no. 5752, pp. 1260-1) explains that:
Because air turbulence can signal that a wing is losing lift, Zook reasoned that the hairs on the Merkel cells might help tell bats when to adjust the angle and curvature of their wings during tight maneuvers to avoid stalling out in midair.
"To test this hypothesis, Zook treated two bats with Nair, a depilating cream more commonly applied to the human bikini zone. Then he videotaped the bats in flight. "They flew perfectly well–in a straight line," he says. But when the bats had to make a 90-degree turn to avoid an obstacle, their elevation control was erratic. "Sometimes they hit the ceiling," Zook says. When the hairs grew back, the bats regained their aviation skills….
Other bat researchers are impressed.
(Thanks to Investigator Jay Passachoff for bringing this to our attention)