Correction

ECOLOGY. For the article “Monarch butterflies (Danaus plexippus L.) use a magnetic compass for navigation” by Jason A. Etheredge, Sandra M. Perez, Orley R. Taylor, and Rudolf Jander, which appeared in number 24, November 23, 1999, of Proc. Natl. Acad. Sci. USA (96, 13845–13846), the authors note the following. “The positive response to magnetic fields in two experiments cannot be repeated. Further experiments show the false positives in these tests result from a positive taxis by the butterflies to the light reflected off the clothing of the observers. We therefore retract our report. We regret the inconvenience that publication of this study may have caused.”